With a CV spanning 82 pages, including more than 340 publications, Professor John Raven’s broad-ranging scientific career has had many highlights. He is a Fellow of both the Royal Societies of London and Edinburgh, an acknowledged expert on algal physiology, ecology and biogeochemistry and, despite retiring in 2008, maintains a punishing international travel schedule whilst still lecturing at the University of Dundee and supervising PhD students.
In aquatic biology study and research , Professor Raven is better known as the co-author of “Aquatic Photosynthesis” first published in 1997 and considered by many as the seminal text in this field.
As a Visiting Fellow and Associate Member of The Plant Functional Biology and Climate Change Cluster (C3) Professor Raven plays an active role in the Algal Biofuels Research Program, gives seminars and is an invaluable mentor to the staff and students in C3.
Fellow of the Royal society of London
Fellow of the Royal Society of Edinburgh
Can supervise: YES
Raven, JA & Giordano, M 2018, 'Acquisition and metabolism of carbon in the Ochrophyta other than diatoms (vol 372, 20160400, 2017)', PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES, vol. 373, no. 1739.View/Download from: Publisher's site
Giordano, M, Olivieri, C, Ratti, S, Norici, A, Raven, JA & Knoll, AH 2018, 'A tale of two eras: Phytoplankton composition influenced by oceanic paleochemistry.', Geobiology, vol. 16, no. 5, pp. 498-506.View/Download from: UTS OPUS or Publisher's site
We report the results of simple experiments which support the hypothesis that changes in ocean chemistry beginning in the Mesozoic Era resulted in an increase in the nutritional quality per mole of C and per cell of planktonic algal biomass compared to earlier phytoplankton. We cultured a cyanobacterium, a diatom, a dinoflagellate, and a green alga in media mimicking aspects of the chemistry of Palaeozoic and Mesozoic-Cenozoic oceans. Substantial differences emerged in the quality of algal biomass between the Palaeozoic and Mesozoic-Cenozoic growth regimes; these differences were strongly affected by interspecific interactions (i.e., the co-existence of different species alters responses to the chemistry of the medium). The change was in the direction of a Mesozoic-Cenozoic biomass enriched in protein per mole C, although cells contained less carbon overall. This would lead to a lower C:N ratio. On the assumption that Mesozoic-Cenozoic grazers' assimilation of total C was similar to that of their earlier counterparts, their diet would be stoichiometrically closer to their C:N requirement. This, along with an increase in mean cell size among continental shelf phytoplankton, could have helped to facilitate observed evolutionary changes in the Mesozoic marine fauna. In turn, increased grazing pressure would have operated as a selective force for the radiation of phytoplankton clades better equipped with antigrazing capabilities (sensu lato), as found widely in phytoplankton with biomineralization. Our results emphasize potential links between changing seawater chemistry, increased predation pressure and the rise to ecological dominance of chlorophyll a+c algae in Mesozoic oceans. The experiments also suggest a potential role for ocean chemistry in changes of marine trophic structure from the Palaeozoic to the later Mesozoic Era.
Lavoie, M, Duval, JFL, Raven, JA, Maps, F, Béjaoui, B, Kieber, DJ & Vincent, WF 2018, 'Carbonate Disequilibrium in the External Boundary Layer of Freshwater Chrysophytes: Implications for Contaminant Uptake.', Environmental Science and Technology, vol. 52, no. 16, pp. 9403-9411.View/Download from: Publisher's site
The interplay between biological and chemical reactions in the freshwater phytoplankton phycosphere and the resulting modulations of contaminant speciation and uptake is poorly characterized. Here we modeled the effect of algal C and N uptake on carbonate cycling and speciation of selected contaminants in the phycosphere (external boundary layer) of chrysophytes, a key phytoplankton group in oligotrophic systems. We calculated an enrichment in H+ concentration relative to that in the bulk solution (pH 7.0) of approximately 40% or a depletion of approximately 30% for NH4+ or NO3--grown cells, respectively, at the algal membrane surface of a 5-m radius cell. Such changes are mainly due to direct H+ uptake or release at the plasmalemma if NO3- or NH4+ is the N source, respectively. Due to these pH changes in the external boundary layer, competition between H+ and metals for uptake is enhanced, for NH4+-grown cells which contributes to a decrease in potential metal uptake. Our model suggests that the uptake of protonated weakly acidic organic acids (HA) is greater in NH4+-grown cells compared to that in NO3--grown cells. The account of chemical reactions in the algal external boundary layer could improve ecological risk assessments for a wide range of contaminants.
De Clerck, O, Kao, S-M, Bogaert, KA, Blomme, J, Foflonker, F, Kwantes, M, Vancaester, E, Vanderstraeten, L, Aydogdu, E, Boesger, J, Califano, G, Charrier, B, Clewes, R, Del Cortona, A, D'Hondt, S, Fernandez-Pozo, N, Gachon, CM, Hanikenne, M, Lattermann, L, Leliaert, F, Liu, X, Maggs, CA, Popper, ZA, Raven, JA, Van Bel, M, Wilhelmsson, PKI, Bhattacharya, D, Coates, JC, Rensing, SA, Van Der Straeten, D, Vardi, A, Sterck, L, Vandepoele, K, Van de Peer, Y, Wichard, T & Bothwell, JH 2018, 'Insights into the Evolution of Multicellularity from the Sea Lettuce Genome.', Current biology : CB, vol. 28, no. 18, pp. 2921-2933.View/Download from: UTS OPUS or Publisher's site
We report here the 98.5 Mbp haploid genome (12,924 protein coding genes) of Ulva mutabilis, a ubiquitous and iconic representative of the Ulvophyceae or green seaweeds. Ulva's rapid and abundant growth makes it a key contributor to coastal biogeochemical cycles; its role in marine sulfur cycles is particularly important because it produces high levels of dimethylsulfoniopropionate (DMSP), the main precursor of volatile dimethyl sulfide (DMS). Rapid growth makes Ulva attractive biomass feedstock but also increasingly a driver of nuisance "green tides." Ulvophytes are key to understanding the evolution of multicellularity in the green lineage, and Ulva morphogenesis is dependent on bacterial signals, making it an important species with which to study cross-kingdom communication. Our sequenced genome informs these aspects of ulvophyte cell biology, physiology, and ecology. Gene family expansions associated with multicellularity are distinct from those of freshwater algae. Candidate genes, including some that arose following horizontal gene transfer from chromalveolates, are present for the transport and metabolism of DMSP. The Ulva genome offers, therefore, new opportunities to understand coastal and marine ecosystems and the fundamental evolution of the green lineage.
Raven, JA 2018, 'The potential effect of low cell osmolarity on cell function through decreased concentration of enzyme substrates.', Journal of experimental botany, vol. 69, no. 20, pp. 4667-4673.View/Download from: UTS OPUS or Publisher's site
Some freshwater algae have lower (<130 osmol m-3) intracellular osmolarities than most others (>180 osmol m-3). Low osmolarities are related to the presence of flagella and the low energy cost of active water efflux following downhill water influx unconstrained by cell walls covering the plasmalemma, and the low resource cost of cell wall synthesis with the same mechanical degree of safety. One consequence of low intracellular osmolarity is limitation on the concentration of metabolites, that is, substrates and products of enzyme activity. Models of the flux through metabolic pathways, and hence the specific growth rate, using steady-state concentrations of enzymes and metabolites have involved organisms with intracellular metabolite osmolarities >280 osmol m-3, where the metabolite concentrations are much greater than the total osmolarity of some freshwater algae. Since the protein concentration (mol m-3) in the cells and the specific growth rates of freshwater cells with low and with higher intracellular osmolarity are highly similar, the models of trade-offs between enzyme and metabolite concentrations for cells with high intracellular osmolarity need modification for cells with low intracellular osmolarity. The soluble free-radical scavenger ascorbate can constitute as little as 0.2% of the low intracellular metabolite concentration (mol m-3) of low-intracellular-osmolarity cells.
© 2018 The Author(s) Published by the Royal Society. All rights reserved. Blue carbon did not originally include macroalgal ecosystems; however evidence is mounting that macroalgal ecosystems function in marine carbon sequestration. The great majority of present day marine macroalgal net primary productivity (NPP) involves haptophytic algae on eroding shores. For these organisms the long-term storage of particulate organic carbon involves export from the site of production of biomass that has evaded parasites and grazers, and that some of the exported biomass is sedimented and stored rather than being mineralized en route by detritivores (microbes and fauna). Export from eroding shores, and subsequent storage, of haptophytic marine macroalgal particulate organic carbon could have started by 1.6 Ga. Storage on depositing shores close to the site of NPP by rhizophytic macroalgae and then by rhizophytic coastal seagrasses, tidal marshes and mangroves began not less than 209 Ma ago. Future increases in surface ocean temperatures may bring tropical marine macroalgae to their upper temperature limit, while temperate marine macroalgae will migrate poleward, in both cases assuming that temperature increases faster than genetic adaptation to higher temperature. Increased CO2 in the surface ocean will generally favour uncalcified over calcified marine macroalgae. This results in decreased CO2 release from decreased calcification, as well as decreased ballasting by CaCO3 of exported particulate organic carbon resulting in decreasing sedimentation. While much more work is needed, the available information suggests that macroalgae play a significant role in marine organic carbon storage.
Kim, M, Brodersen, KE, Szabó, M, Larkum, AWD, Raven, JA, Ralph, PJ & Pernice, M 2018, 'Low oxygen affects photophysiology and the level of expression of two-carbon metabolism genes in the seagrass Zostera muelleri.', Photosynthesis Research, vol. 136, no. 2, pp. 147-160.View/Download from: UTS OPUS or Publisher's site
Seagrasses are a diverse group of angiosperms that evolved to live in shallow coastal waters, an environment regularly subjected to changes in oxygen, carbon dioxide and irradiance. Zostera muelleri is the dominant species in south-eastern Australia, and is critical for healthy coastal ecosystems. Despite its ecological importance, little is known about the pathways of carbon fixation in Z. muelleri and their regulation in response to environmental changes. In this study, the response of Z. muelleri exposed to control and very low oxygen conditions was investigated by using (i) oxygen microsensors combined with a custom-made flow chamber to measure changes in photosynthesis and respiration, and (ii) reverse transcription quantitative real-time PCR to measure changes in expression levels of key genes involved in C4 metabolism. We found that very low levels of oxygen (i) altered the photophysiology of Z. muelleri, a characteristic of C3 mechanism of carbon assimilation, and (ii) decreased the expression levels of phosphoenolpyruvate carboxylase and carbonic anhydrase. These molecular-physiological results suggest that regulation of the photophysiology of Z. muelleri might involve a close integration between the C3 and C4, or other CO2 concentrating mechanisms metabolic pathways. Overall, this study highlights that the photophysiological response of Z. muelleri to changing oxygen in water is capable of rapid acclimation and the dynamic modulation of pathways should be considered when assessing seagrass primary production.
Zavřel, T, Szabó, M, Tamburic, B, Evenhuis, C, Kuzhiumparambil, U, Literáková, P, Larkum, AWD, Raven, JA, Červený, J & Ralph, PJ 2018, 'Effect of carbon limitation on photosynthetic electron transport in Nannochloropsis oculata.', Journal of photochemistry and photobiology. B, Biology, vol. 181, pp. 31-43.View/Download from: UTS OPUS or Publisher's site
This study describes the impacts of inorganic carbon limitation on the photosynthetic efficiency and operation of photosynthetic electron transport pathways in the biofuel-candidate microalga Nannochloropsis oculata. Using a combination of highly-controlled cultivation setup (photobioreactor), variable chlorophyll a fluorescence and transient spectroscopy methods (electrochromic shift (ECS) and P700 redox kinetics), we showed that net photosynthesis and effective quantum yield of Photosystem II (PSII) decreased in N. oculata under carbon limitation. This was accompanied by a transient increase in total proton motive force and energy-dependent non-photochemical quenching as well as slightly elevated respiration. On the other hand, under carbon limitation the rapid increase in proton motive force (PMF, estimated from the total ECS signal) was also accompanied by reduced conductivity of ATP synthase to protons (estimated from the rate of ECS decay in dark after actinic illumination). This indicates that the slow operation of ATP synthase results in the transient build-up of PMF, which leads to the activation of fast energy dissipation mechanisms such as energy-dependent non-photochemical quenching. N. oculata also increased content of lipids under carbon limitation, which compensated for reduced NAPDH consumption during decreased CO2 fixation. The integrated knowledge of the underlying energetic regulation of photosynthetic processes attained with a combination of biophysical methods may be used to identify photo-physiological signatures of the onset of carbon limitation in microalgal cultivation systems, as well as to potentially identify microalgal strains that can better acclimate to carbon limitation.
Pierangelini, M, Raven, JA & Giordano, M 2017, 'The relative availability of inorganic carbon and inorganic nitrogen influences the response of the dinoflagellate Protoceratium reticulatum to elevated CO2.', Journal of Phycology, vol. 53, no. 2, pp. 298-307.View/Download from: UTS OPUS or Publisher's site
This work originates from three facts: 1) changes in CO2 availability influence metabolic processes in algal cells. 2) Spatial and temporal variations of nitrogen availability cause repercussions on phytoplankton physiology. 3) Growth and cell composition are dependent on the stoichiometry of nutritional resources. In this study we assess whether the impact of rising pCO2 is influenced by N availability, through the impact that it would have on the C/N stoichiometry, in condition of N sufficiency. Our experiments used the dinoflagellate Protoceratium reticulatum, which we cultured under three CO2 regimes (400, 1000 and 5000 ppmv, pH of 8.1) and either variable (the NO3 (-) concentration was always 2.5 mmol * L(-1) ) or constant (NO3 (-) concentration varied to maintain the same Ci /NO3 (-) ratio at all pCO2 ) Ci /NO3 (-) ratio. Regardless of N availability, cells had higher specific growth rates, but lower cell dry weight and C and N quotas, at elevated CO2 . The carbohydrate pool size and the C/N was unaltered in all treatments. The lipid content only decreased at high pCO2 at constant Ci /NO3 (-) ratio. In the variable Ci /NO3 (-) conditions, the relative abundance of Rubisco (and other proteins) also changed; this did not occur at constant Ci /NO3 (-) . Thus, the biomass quality of P. reticulatum for grazers was affected by the Ci /NO3 (-) ratio in the environment and not only by the pCO2 , both with respect to the size of the main organic pools and the composition of the expressed proteome. This article is protected by copyright. All rights reserved.
Wells, ML, Potin, P, Craigie, JS, Raven, JA, Merchant, SS, Helliwell, KE, Smith, AG, Camire, ME & Brawley, SH 2017, 'Algae as nutritional and functional food sources: revisiting our understanding', Journal of Applied Phycology, vol. 29, no. 2, pp. 949-982.View/Download from: UTS OPUS or Publisher's site
© 2016 The Author(s)Global demand for macroalgal and microalgal foods is growing, and algae are increasingly being consumed for functional benefits beyond the traditional considerations of nutrition and health. There is substantial evidence for the health benefits of algal-derived food products, but there remain considerable challenges in quantifying these benefits, as well as possible adverse effects. First, there is a limited understanding of nutritional composition across algal species, geographical regions, and seasons, all of which can substantially affect their dietary value. The second issue is quantifying which fractions of algal foods are bioavailable to humans, and which factors influence how food constituents are released, ranging from food preparation through genetic differentiation in the gut microbiome. Third is understanding how algal nutritional and functional constituents interact in human metabolism. Superimposed considerations are the effects of harvesting, storage, and food processing techniques that can dramatically influence the potential nutritive value of algal-derived foods. We highlight this rapidly advancing area of algal science with a particular focus on the key research required to assess better the health benefits of an alga or algal product. There are rich opportunities for phycologists in this emerging field, requiring exciting new experimental and collaborative approaches.
Cl(-) is an essential micronutrient for oxygenic photolithotrophs. About half of global primary productivity is carried out by oxygenic photolithotrophs exposed to saline waters with Cl(-) concentrations orders of magnitude higher than that needed to satisfy the micronutrient requirement. The other half of primary productivity involves terrestrial and freshwater glycophytes sometimes in environments containing significantly more Cl(-) than is needed for the micronutrient requirement, but less than the toxic Cl(-) concentration for glycophytes. Intracellular Cl(-) acts in regulation of cell turgor and volume, including that of stomatal and pulvinar nastic movements, is a major ion in streptophyte and ulvophycean action potentials, and is involved in ion currents flowing around apices of pollen tubes and Acetabularia cells. More work is needed on the essentiality of Cl(-) in these processes, as well as the recent finding that Cl(-) at 1-5 mol m(-3) increases water use efficiency of growth and leaf area in Nicotiana tabacum.
Knowing the potential maximum photoautotrophic growth rate for planktonic primary producers is fundamental to our understanding of trophic and biogeochemical processes, and of importance in applied phycology. When day-integrated C-specific growth is considered over natural light:dark cycles, plausible RuBisCO activity (Kcat coupled with cellular RuBisCO content) caps growth to less than a few doubling per day. Prolonged periods of C-specific growth rates above ca. 1.3 d1 thus appear increasingly implausible. Discrepancies between RuBisCO-capped rates and reported microalgal-specific growth rates, including temperature–growth rate relationships, may be explained by transformational errors in growth rate determinations made by reference to cell counts or most often chlorophyll, or by extrapolations from short-term measurements. Coupled studies of enzyme activity and day-on-day C-specific growth rates are required to provide definitive evidence of high growth rates. It seems likely, however, that selective pressure to evolve a RuBisCO with a high Kcat (with a likely concomitant increase in Km for CO2) would be low, as other factors such as light limitation (developing during biomass growth due to self-shading), nutrient limitations, CO2 depletion and pH elevation, would all rapidly depress realized specific growth rates.
Contents 516 I. 516 II. 518 III. 518 IV. 521 V. 523 VI. 523 VII. 526 526 References 526 SUMMARY: The relevance of infochemicals in the relationships between organisms is emerging as a fundamental aspect of aquatic ecology. Exchanges of chemical cues are likely to occur not only between organisms of different species, but also between conspecific individuals. Especially intriguing is the investigation of chemical communication in microalgae, because of the relevance of these organisms for global primary production and their key role in trophic webs. Intraspecific communication between algae has been investigated mostly in relation to sexuality and mating. The literature also contains information on other types of intraspecific chemical communication that have not always been explicitly tagged as ways to communicate to conspecifics. However, the proposed role of certain compounds as intraspecific infochemicals appears questionable. In this article, we make use of this plethora of information to describe the various instances of intraspecific chemical communication between conspecific microalgae and to identify the common traits and ecological significance of intraspecific communication. We also discuss the evolutionary implications of intraspecific chemical communication and the mechanisms by which it can be inherited. A special focus is the genetic diversity among conspecific algae, including the possibility that genetic diversity is an absolute requirement for intraspecific chemical communication.
Ruan, Z, Raven, JA & Giordano, M 2017, 'In Synechococcus sp competition for energy between assimilation and acquisition of C and those of N only occurs when growth is light limited', JOURNAL OF EXPERIMENTAL BOTANY, vol. 68, no. 14, pp. 3829-3839.View/Download from: UTS OPUS or Publisher's site
Raven, JA, Beardall, J & Sanchez-Baracaldo, P 2017, 'The possible evolution and future of CO2-concentrating mechanisms', JOURNAL OF EXPERIMENTAL BOTANY, vol. 68, no. 14, pp. 3701-3716.View/Download from: UTS OPUS or Publisher's site
Raven, JA & Giordano, M 2017, 'Acquisition and metabolism of carbon in the Ochrophyta other than diatoms', PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES, vol. 372, no. 1728.View/Download from: UTS OPUS or Publisher's site
Leles, SG, Mitra, A, Flynn, KJ, Stoecker, DK, Hansen, PJ, Calbet, A, McManus, GB, Sanders, RW, Caron, DA, Not, F, Hallegraeff, GM, Pitta, P, Raven, JA, Johnson, MD, Glibert, PM & Våge, S 2017, 'Oceanic protists with different forms of acquired phototrophy display contrasting biogeographies and abundance.', Proceedings of the Royal Society B: Biological Sciences, vol. 284, no. 1860, pp. 1-6.View/Download from: UTS OPUS or Publisher's site
This first comprehensive analysis of the global biogeography of marine protistan plankton with acquired phototrophy shows these mixotrophic organisms to be ubiquitous and abundant; however, their biogeography differs markedly between different functional groups. These mixotrophs, lacking a constitutive capacity for photosynthesis (i.e. non-constitutive mixotrophs, NCMs), acquire their phototrophic potential through either integration of prey-plastids or through endosymbiotic associations with photosynthetic microbes. Analysis of field data reveals that 40-60% of plankton traditionally labelled as (non-phototrophic) microzooplankton are actually NCMs, employing acquired phototrophy in addition to phagotrophy. Specialist NCMs acquire chloroplasts or endosymbionts from specific prey, while generalist NCMs obtain chloroplasts from a variety of prey. These contrasting functional types of NCMs exhibit distinct seasonal and spatial global distribution patterns. Mixotrophs reliant on 'stolen' chloroplasts, controlled by prey diversity and abundance, dominate in high-biomass areas. Mixotrophs harbouring intact symbionts are present in all waters and dominate particularly in oligotrophic open ocean systems. The contrasting temporal and spatial patterns of distribution of different mixotroph functional types across the oceanic provinces, as revealed in this study, challenges traditional interpretations of marine food web structures. Mixotrophs with acquired phototrophy (NCMs) warrant greater recognition in marine research.
Sanchez-Baracaldo, P, Raven, JA, Pisani, D & Knoll, AH 2017, 'Early photosynthetic eukaryotes inhabited low-salinity habitats', PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, vol. 114, no. 37, pp. E7737-E7745.View/Download from: UTS OPUS or Publisher's site
Raven, JA 2017, 'The possible roles of algae in restricting the increase in atmospheric CO2 and global temperature', EUROPEAN JOURNAL OF PHYCOLOGY, vol. 52, no. 4, pp. 506-522.View/Download from: UTS OPUS or Publisher's site
Sanchez-Baracaldo, P, Bianchini, G, Huelsenbeck, JP, Raven, JA, Pisani, D & Knoll, AH 2017, 'REPLY TO NAKOV ET AL.: Model choice requires biological insight when studying the ancestral habitat of photosynthetic eukaryotes', PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, vol. 114, no. 50, pp. E10608-E10609.View/Download from: UTS OPUS or Publisher's site
Larkum, AWD, Davey, PA, Kuo, J, Ralph, PJ & Raven, JA 2017, 'Carbon-concentrating mechanisms in seagrasses.', Journal of Experimental Botany, vol. 68, no. 14, pp. 3773-3784.View/Download from: UTS OPUS or Publisher's site
Seagrasses are unique angiosperms that carry out growth and reproduction submerged in seawater. They occur in at least three families of the Alismatales. All have chloroplasts mainly in the cells of the epidermis. Living in seawater, the supply of inorganic carbon (Ci) to the chloroplasts is diffusion limited, especially under unstirred conditions. Therefore, the supply of CO2 and bicarbonate across the diffusive boundary layer on the outer side of the epidermis is often a limiting factor. Here we discuss the evidence for mechanisms that enhance the uptake of Ci into the epidermal cells. Since bicarbonate is plentiful in seawater, a bicarbonate pump might be expected; however, the evidence for such a pump is not strongly supported. There is evidence for a carbonic anhydrase outside the outer plasmalemma. This, together with evidence for an outward proton pump, suggests the possibility that local acidification leads to enhanced concentrations of CO2 adjacent to the outer tangential epidermal walls, which enhances the uptake of CO2, and this could be followed by a carbon-concentrating mechanism (CCM) in the cytoplasm and/or chloroplasts. The lines of evidence for such an epidermal CCM are discussed, including evidence for special 'transfer cells' in some but not all seagrass leaves in the tangential inner walls of the epidermal cells. It is concluded that seagrasses have a CCM but that the case for concentration of CO2 at the site of Rubisco carboxylation is not proven.
Lavoie, M, Raven, JA, Jones, OAH & Qian, H 2016, 'Energy cost of intracellular metal and metalloid detoxification in wild-type eukaryotic phytoplankton', METALLOMICS, vol. 8, no. 10, pp. 1097-1109.View/Download from: UTS OPUS or Publisher's site
Glibert, PM, Wilkerson, FP, Dugdale, RC, Raven, JA, Dupont, CL, Leavitt, PR, Parker, AE, Burkholder, JM & Kana, T 2016, 'Pluses and minuses of ammonium and nitrate uptake and assimilation by phytoplankton and implications for productivity and community composition, with emphasis on nitrogen-enriched conditions', Limnology and Oceanography, vol. 61, pp. 165-197.View/Download from: UTS OPUS or Publisher's site
Anthropogenic activities are altering total nutrient loads to many estuaries and freshwaters, resulting in high loads not only of total nitrogen (N), but in some cases, of chemically reduced forms, notably NH1 4 . Long thought to be the preferred form of N for phytoplankton uptake, NH1 4 may actually suppress overall growth when concentrations are sufficiently high. NH14 has been well known to be inhibitory or repressive for NO-3 uptake and assimilation, but the concentrations of NH1 4 that promote vs. repress NO- 3 uptake, assimilation, and growth in different phytoplankton groups and under different growth conditions are not well understood. Here, we review N metabolism first in a 'generic' eukaryotic cell, and the contrasting metabolic pathways and regulation of NH1 4 and NO2 3 when these substrates are provided individually under equivalent growth conditions. Then the metabolic interactions of these substrates are described when both are provided together, emphasizing the cellular challenge of balancing nutrient acquisition with photosynthetic energy balance in dynamic environments. Conditions under which dissipatory pathways such as dissimilatory NO2 3 / NO2 2 reduction to NH1 4 and photorespiration that may lead to growth suppression are highlighted. While more is known about diatoms, taxon-specific differences in NH14
and NO2 3 metabolism that may contribute to changes in phytoplankton community composition when the composition of the N pool changes are presented. These relationships have important implications for harmful algal blooms, development of nutrient criteria for management, and modeling of nutrient uptake by phytoplankton, particularly in conditions where eutrophication is increasing and the redox state of N loads is changing.
Lavoie, M, Raven, J & Levasseur, M 2016, 'Energy cost and putative benefits of cellular mechanisms modulating buoyancy in aflagellate marine phytoplankton', European Journal of Phycology, vol. 52, no. 2, pp. 239-251.View/Download from: UTS OPUS or Publisher's site
Little information is available on the energetics of buoyancy modulation in aflagellate phytoplankton, which comprise the majority of autotrophic cells found in the ocean. Here we computed for three aflagellate species of marine phytoplankton (Emiliania huxleyi, Thalassiosira pseudonana, and Ethmodiscus rex) the theoretical minimum energy cost as photons absorbed and nitrogen resource required of the key physiological mechanisms (i.e. replacement of quaternary ammonium by dimethylsulfoniopropionate, storage of polysaccharides, and cell wall biosynthesis) affecting the cell's vertical movement as a function of nitrogen (N) availability. These energy costs were also normalized to the capacity of each buoyancy mechanism to modulate sinking or rising rates based on Stokes' law. The three physiological mechanisms could act as ballast in the three species tested in conditions of low N availability at a low fraction (<11.9%) of the total photon energy cost for growth. Cell wall formation in E. huxleyi was the least costly ballast strategy whereas in T. pseudonana the photon energy cost of the three ballast strategies were similar. In E. rex, carbohydrate storage and mobilization appear to be energetically cheaper than modulations in organic solute synthesis to achieve vertical migration. This supports the carbohydrate ballast strategy for vertical migration for this species, but argues against the theory of replacement of low or high density organic solutes. The present study brings new insights into the energy cost and potential selective advantage of several strategies modulating the buoyancy of aflagellate marine phytoplankton.
Raven, JA & Colmer, TD 2016, 'Life at the boundary: photosynthesis at the soil-fluid interface. A synthesis focusing on mosses', JOURNAL OF EXPERIMENTAL BOTANY, vol. 67, no. 6, pp. 1613-1623.View/Download from: UTS OPUS or Publisher's site
Mitra, A, Flynn, KJ, Tillmann, U, Raven, JA, Caron, D, Stoecker, DK, Not, F, Hansen, PJ, Hallegraeff, G, Sanders, R, Wilken, S, McManus, G, Johnson, M, Pitta, P, Vage, S, Berge, T, Calbet, A, Thingstad, F, Jeong, HJ, Burkholder, J, Glibert, PM, Graneli, E & Lundgren, V 2016, 'Defining Planktonic Protist Functional Groups on Mechanisms for Energy and Nutrient Acquisition: Incorporation of Diverse Mixotrophic Strategies', PROTIST, vol. 167, no. 2, pp. 106-120.View/Download from: Publisher's site
Stocker, BD, Prentice, IC, Cornell, SE, Davies-Barnard, T, Finzi, AC, Franklin, O, Janssens, I, Larmola, T, Manzoni, S, Nasholm, T, Raven, JA, Rebel, KT, Reed, S, Vicca, S, Wiltshire, A & Zaehle, S 2016, 'Terrestrial nitrogen cycling in Earth system models revisited', NEW PHYTOLOGIST, vol. 210, no. 4, pp. 1165-1168.View/Download from: UTS OPUS or Publisher's site
Forgan, DH, Mead, A, Cockell, CS & Raven, JA 2015, 'Surface flux patterns on planets in circumbinary systems and potential for photosynthesis', International Journal of Astrobiology, vol. 14, no. 3, pp. 465-478.View/Download from: UTS OPUS or Publisher's site
Copyright © Cambridge University Press 2014. Recently, the Kepler Space Telescope has detected several planets in orbit around a close binary star system. These so-called circumbinary planets will experience non-trivial spatial and temporal distributions of radiative flux on their surfaces, with features not seen in their single-star orbiting counterparts. Earth-like circumbinary planets inhabited by photosynthetic organisms will be forced to adapt to these unusual flux patterns. We map the flux received by putative Earth-like planets (as a function of surface latitude/longitude and time) orbiting the binary star systems Kepler-16 and Kepler-47, two star systems which already boast circumbinary exoplanet detections. The longitudinal and latitudinal distribution of flux is sensitive to the centre-of-mass motion of the binary, and the relative orbital phases of the binary and planet. Total eclipses of the secondary by the primary, as well as partial eclipses of the primary by the secondary add an extra forcing term to the system. We also find that the patterns of darkness on the surface are equally unique. Beyond the planet's polar circles, the surface spends a significantly longer time in darkness than latitudes around the equator, due to the stars' motions delaying the first sunrise of spring (or hastening the last sunset of autumn). In the case of Kepler-47, we also find a weak longitudinal dependence for darkness, but this effect tends to average out if considered over many orbits. In the light of these flux and darkness patterns, we consider and discuss the prospects and challenges for photosynthetic organisms, using terrestrial analogues as a guide.
O'Malley-James, JT, Greaves, JS, Raven, JA & Cockell, CS 2015, 'In search of future earths: assessing the possibility of finding Earth analogues in the later stages of their habitable lifetimes.', Astrobiology, vol. 15, no. 5, pp. 400-411.View/Download from: UTS OPUS or Publisher's site
Earth will become uninhabitable within 2-3 Gyr as a result of the increasing luminosity of the Sun changing the boundaries of the habitable zone (HZ). Predictions about the future of habitable conditions on Earth include declining species diversity and habitat extent, ocean loss, and changes to geochemical cycles. Testing these predictions is difficult, but the discovery of a planet that is an analogue to future Earth could provide the means to test them. This planet would need to have an Earth-like biosphere history and to be approaching the inner edge of the HZ at present. Here, we assess the possibility of finding such a planet and discuss the benefits of analyzing older Earths. Finding an old-Earth analogue in nearby star systems would be ideal, because this would allow for atmospheric characterization. Hence, as an illustrative example, G stars within 10 pc of the Sun are assessed as potential old-Earth-analog hosts. Six of these represent good potential hosts. For each system, a hypothetical Earth analogue is placed at locations within the continuously habitable zone (CHZ) that would allow enough time for Earth-like biosphere development. Surface temperature evolution over the host star's main sequence lifetime (assessed by using a simple climate model) is used to determine whether the planet would be in the right stage of its late-habitable lifetime to exhibit detectable biosignatures. The best candidate, in terms of the chances of planet formation in the CHZ and of biosignature detection, is 61 Virginis. However, planet formation studies suggest that only a small fraction (0.36%) of G stars in the solar neighborhood could host an old-Earth analogue. If the development of Earth-like biospheres is rare, requiring a sequence of low-probability events to occur, biosphere evolution models suggest they are rarer still, with only thousands being present in the Galaxy as a whole.
Raven, JA & Griffiths, H 2015, 'Photosynthesis in reproductive structures: costs and benefits', JOURNAL OF EXPERIMENTAL BOTANY, vol. 66, no. 7, pp. 1699-1705.View/Download from: UTS OPUS or Publisher's site
Giordano, M, Palmucci, M & Raven, JA 2015, 'Growth rate hypothesis and efficiency of protein synthesis under different sulphate concentrations in two green algae', PLANT CELL AND ENVIRONMENT, vol. 38, no. 11, pp. 2313-2317.View/Download from: UTS OPUS or Publisher's site
Raven, JA 2015, 'Implications of mutation of organelle genomes for organelle function and evolution.', Journal of experimental botany, vol. 66, no. 19, pp. 5639-5650.View/Download from: UTS OPUS or Publisher's site
Organelle genomes undergo more variation, including that resulting from damage, than eukaryotic nuclear genomes, or bacterial genomes, under the same conditions. Recent advances in characterizing the changes to genomes of chloroplasts and mitochondria of Zea mays should, when applied more widely, help our understanding of how damage to organelle genomes relates to how organelle function is maintained through the life of individuals and in succeeding generations. Understanding of the degree of variation in the changes to organelle DNA and its repair among photosynthetic organisms might help to explain the variations in the rate of nucleotide substitution among organelle genomes. Further studies of organelle DNA variation, including that due to damage and its repair might also help us to understand why the extent of DNA turnover in the organelles is so much greater than that in their bacterial (cyanobacteria for chloroplasts, proteobacteria for mitochondria) relatives with similar rates of production of DNA-damaging reactive oxygen species. Finally, from the available data, even the longest-lived organelle-encoded proteins, and the RNAs needed for their synthesis, are unlikely to maintain organelle function for much more than a week after the complete loss of organelle DNA.
Edwards, D, Cherns, L & Raven, JA 2015, 'Could land-based early photosynthesizing ecosystems have bioengineered the planet in mid-Palaeozoic times?', PALAEONTOLOGY, vol. 58, no. 5, pp. 803-837.View/Download from: UTS OPUS or Publisher's site
Flynn, KJ, St John, M, Raven, JA, Skibinski, DOF, Allen, JI, Mitra, A & Hofmann, EE 2015, 'HORIZONS: Acclimation, adaptation, traits and trade-offs in plankton functional type models: Reconciling terminology for biology and modelling', Journal of Plankton Research, vol. 37, no. 4, pp. 683-691.View/Download from: UTS OPUS or Publisher's site
© 2015 The Author 2015. Published by Oxford University Press. All rights reserved. For permissions, please email: email@example.com. We propose definitions in terminology to enhance ongoing collaborations between biologists and modellers on plankton ecology. Organism "functional type" should refer to commonality in ecology not biogeochemistry; the latter is largely an emergent property of the former, while alignment with ecology is also consistent with usage in terrestrial science. Adaptation should be confined, as in genetics, to consideration of species inter-generational change; most so-called "adaptive" plankton models are thus acclimative, modifying vital rates in response to stimuli. Trait trade-off approaches should ideally only be considered for describing intra-generational interactions; in applications between generations, and certainly between unrelated species, such concepts should be avoided. We suggest that s ystems biology approaches, through to complex adaptive/acclimative systems modelling, with explicit modelling of feedback processes (which we suggest should define "mechanistic" models), would provide realistic and flexible bases upon which to develop descriptions of functional type models.
Tamburic, B, Evenhuis, CR, Suggett, DJ, Larkum, AWD, Raven, JA & Ralph, PJ 2015, 'Gas Transfer Controls Carbon Limitation During Biomass Production by Marine Microalgae', CHEMSUSCHEM, vol. 8, no. 16, pp. 2727-2736.View/Download from: UTS OPUS or Publisher's site
Radford, D, Szabo, M, Raven, J & Ralph, PJ 2015, 'SATISFYING THE NUTRIENT TANK OF NANNOCHLOROPSIS OCULATA; CO-LIMITATION REDUCES FILLING EFFICIENCY', EUROPEAN JOURNAL OF PHYCOLOGY, vol. 50, pp. 138-139.
Raven, J & Ralph, PJ 2015, 'Enhanced biofuel production using optimality, pathway modification and waste minimization', Journal of Applied Phycology, vol. 27, pp. 1-31.View/Download from: UTS OPUS or Publisher's site
In response to their environment, algae in the wild may use an approximation to optimality of resource allocation in cellular structures, photosynthetic pigments, enzymes, transporters in membranes and RNAs and in their genetic material. However, under controlled conditions, when algae are grown for biofuel (lipid) production for example, some of these processes can be altered to increase the efficiency of photosynthesis and therefore, lipid yield. This suggests that there is scope for selecting mutations and for genetic engineering at various levels in the photosynthetic apparatus with the aim of increasing efficiency of photon use and the rate of transformation of resources per unit biomass to improve biofuel yields. More specifically, the wavelength range covered by photosynthetic pigments and photochemical reaction centres could be increased, the number of protons transported from the thylakoid lumen to the stroma per unit ATP synthesised by the ATP synthetase could be decreased, the fluctuating light effect could be utilised and photosynthetic pathways changed, e.g. replacing part or all of the current machinery for autotrophic fixation of inorganic carbon. There are also possibilities for decreasing carbon loss by decreasing `wasteful aspects of dark respiration and of dissolved organic carbon loss. Provided that the environmental fluctuations to which algal growth conditions are constrained, there are possibilities for decreasing the resource costs of protection from ROS, and by down-regulating photoprotective mechanisms, as well as limiting the capacity to repair processes related to photoinhibition. Decreased protein turnover is also a potential energetic saving. These interventions apply to individual processes; however, this may not be immediately incorporated into the optimal allocation of resources by the alga, and further intervention using a system biology approach may be required.
Raven, JA & Doblin, MA 2014, 'Active water transport in unicellular algae: where, why, and how', JOURNAL OF EXPERIMENTAL BOTANY, vol. 65, no. 22, pp. 6279-6292.View/Download from: UTS OPUS or Publisher's site
Brown, SP, Mead, AJ, Forgan, DH, Raven, JA & Cockell, CS 2014, 'Photosynthetic potential of planets in 3 : 2 spin-orbit resonances', International Journal of Astrobiology, vol. 13, no. 4, pp. 279-289.View/Download from: UTS OPUS or Publisher's site
© Cambridge University Press 2014. Photosynthetic life requires sufficient photosynthetically active radiation to metabolize. On Earth, plant behaviour, physiology and metabolism are sculpted around the night-day cycle by an endogenous biological circadian clock. The evolution of life was influenced by the Earth-Sun orbital dynamic, which generates the photo-environment incident on the planetary surface. In this work, the unusual photo-environment of an Earth-like planet (ELP) in 3 : 2 spin-orbit resonance is explored. Photo-environments on the ELP are longitudinally differentiated, in addition to differentiations related to latitude and depth (for aquatic organisms) which are familiar on Earth. The light environment on such a planet could be compatible with Earth's photosynthetic life although the threat of atmospheric freeze-out and prolonged periods of darkness would present significant challenges. We emphasize the relationship between the evolution of life on a planetary body with its orbital dynamics.
O'Malley-James, JT, Cockell, CS, Greaves, JS & Raven, JA 2014, 'Swansong biospheres II: the final signs of life on terrestrial planets near the end of their habitable lifetimes', INTERNATIONAL JOURNAL OF ASTROBIOLOGY, vol. 13, no. 3, pp. 229-243.View/Download from: UTS OPUS or Publisher's site
Mitra, A, Flynn, KJ, Burkholder, JM, Berge, T, Calbet, A, Raven, JA, Granéli, E, Glibert, PM, Hansen, PJ, Stoecker, DK, Thingstad, F, Tillmann, U, Väge, S, Wilken, S & Zubkov, MV 2014, 'The role of mixotrophic protists in the biological carbon pump', Biogeosciences, vol. 11, no. 4, pp. 995-1005.View/Download from: UTS OPUS or Publisher's site
The traditional view of the planktonic food web describes consumption of inorganic nutrients by photoautotrophic phytoplankton, which in turn supports zooplankton and ultimately higher trophic levels. Pathways centred on bacteria provide mechanisms for nutrient recycling. This structure lies at the foundation of most models used to explore biogeochemical cycling, functioning of the biological pump, and the impact of climate change on these processes. We suggest an alternative new paradigm, which sees the bulk of the base of this food web supported by protist plankton communities that are mixotrophic-combining phototrophy and phagotrophy within a single cell. The photoautotrophic eukaryotic plankton and their heterotrophic microzooplankton grazers dominate only during the developmental phases of ecosystems (e.g. spring bloom in temperate systems). With their flexible nutrition, mixotrophic protists dominate in more-mature systems (e.g. temperate summer, established eutrophic systems and oligotrophic systems); the more-stable water columns suggested under climate change may also be expected to favour these mixotrophs. We explore how such a predominantly mixotrophic structure affects microbial trophic dynamics and the biological pump. The mixotroph-dominated structure differs fundamentally in its flow of energy and nutrients, with a shortened and potentially more efficient chain from nutrient regeneration to primary production. Furthermore, mixotrophy enables a direct conduit for the support of primary production from bacterial production. We show how the exclusion of an explicit mixotrophic component in studies of the pelagic microbial communities leads to a failure to capture the true dynamics of the carbon flow. In order to prevent a misinterpretation of the full implications of climate change upon biogeochemical cycling and the functioning of the biological pump, we recommend inclusion of multi-nutrient mixotroph models within ecosystem studies. © 2014 Author(s)...
Brodie, J, Williamson, CJ, Smale, D, Kamenos, KA, Mieszkowska, N, Santos, R, Cunliffe, M, Steinke, M, Yesson, C, Anderson, KM, Asnaghi, V, Brownlee C, Burdett, HL, Burrows, MT, Collins, S, Donahue, PJC, Harvey, B, Foggo, A, Noisette, F, Nunes, J, Ragazzola, F, Raven, JA, Schmidt, DN, Suggett, DJ, Teichberg, M & Hall-Spencer, JM 2014, 'The future of the northeast Atlantic benthic flora in a high CO2 world', Ecology & Evolution, vol. 4, no. 13, pp. 2787-2798.View/Download from: UTS OPUS or Publisher's site
Seaweed and seagrass communities in the northeast Atlantic have been profoundly impacted by humans, and the rate of change is accelerating rapidly due to runaway CO2 emissions and mounting pressures on coastlines associated with human population growth and increased consumption of finite resources. Here, we predict how rapid warming and acidification are likely to affect benthic flora and coastal ecosystems of the northeast Atlantic in this century, based on global evidence from the literature as interpreted by the collective knowledge of the authorship. We predict that warming will kill off kelp forests in the south and that ocean acidification will remove maerl habitat in the north. Seagrasses will proliferate, and associated epiphytes switch from calcified algae to diatoms and filamentous species. Invasive species will thrive in niches liberated by loss of native species and spread via exponential development of artificial marine structures. Combined impacts of seawater warming, ocean acidification, and increased storminess may replace structurally diverse seaweed canopies, with associated calcified and noncalcified flora, with simple habitats dominated by noncalcified, turf-forming seaweeds.
Algae frequently get a bad press. Pond slime is a problem in garden pools, algal blooms can produce toxins that incapacitate or kill animals and humans and even the term seaweed is pejorative - a weed being a plant growing in what humans consider to be the wrong place. Positive aspects of algae are generally less newsworthy - they are the basis of marine food webs, supporting fisheries and charismatic marine megafauna from albatrosses to whales, as well as consuming carbon dioxide and producing oxygen. Here we consider what algae are, their diversity in terms of evolutionary origin, size, shape and life cycles, and their role in the natural environment and in human affairs.
Sánchez-Baracaldo, P, Ridgwell, A & Raven, JA 2014, 'A neoproterozoic transition in the marine nitrogen cycle.', Current Biology, vol. 24, no. 6, pp. 652-657.View/Download from: UTS OPUS or Publisher's site
The Neoproterozoic (1000-542 million years ago, Mya) was characterized by profound global environmental and evolutionary changes, not least of which included a major rise in atmospheric oxygen concentrations [1, 2], extreme climatic fluctuations and global-scale glaciation , and the emergence of metazoan life in the oceans [4, 5]. We present here phylogenomic (135 proteins and two ribosomal RNAs, SSU and LSU) and relaxed molecular clock (SSU, LSU, and rpoC1) analyses that identify this interval as a key transition in the marine nitrogen cycle. Specifically, we identify the Cryogenian (850-635 Mya) as heralding the first appearance of both marine planktonic unicellular nitrogen-fixing cyanobacteria and non-nitrogen-fixing picocyanobacteria (Synechococcus and Prochlorococcus ). Our findings are consistent with the existence of open-ocean environmental conditions earlier in the Proterozoic adverse to nitrogen-fixers and their evolution-specifically, insufficient availability of molybdenum and vanadium, elements essential to the production of high-yielding nitrogenases. As these elements became more abundant during the Cryogenian [7, 8], both nitrogen-fixing cyanobacteria and planktonic picocyanobacteria diversified. The subsequent emergence of a strong biological pump in the ocean implied by our evolutionary reconstruction may help in explaining increased oxygenation of the Earth's surface at this time, as well as tendency for glaciation.
Raven, J, Beardall, J & Giordano, M 2014, 'Energy costs of carbon dioxide concentration mechanisms in aquatic organisms', Photosynthesis Research, vol. 121, no. 2-Mar, pp. 111-124.View/Download from: Publisher's site
© 2014 Elsevier B.V. Nitrogen and sulfur are abundant constituents of plant and algal cells that are assimilated at the lowest oxidation number, as NH 4 + and S 2- , although they can (in the case of sulfur, usually must) be acquired with their highest oxidation number, as NO 3 - and SO 4 2- . Some occasional differences and variants exists for transport and assimilation systems; the greatest differences in the way vascular plants and algae use N and S, however, most probably resides in regulation. For instance, nitrate assimilation in plants is strongly regulated by phosphorylation. In algae, redox regulation appears to be more important. Similarly, sulfate reduction has its main control step at the level of APS reductase in higher plants, whereas in algae a redox regulation has been recently been hypothesized for ATP sulfurylase, the first step in sulfate assimilation. Unfortunately, the information on the regulation of N and S acquisition and assimilation is limited to very few species (e.g. Chlamydomonas reinhardtii, Arabidopsis thaliana) this is especially true in the case of sulfur. This review attempts to highlight the points of divergence in N and S utilization by plants and algae, leaving aside the biochemical details and the features that do not show any obvious difference.
Sulpice, R, Ishihara, H, Schlereth, A, Cawthray, GR, Encke, B, Giavalisco, P, Ivakov, A, Arrivault, S, Jost, R, Krohn, N, Kuo, J, Laliberté, E, Pearse, SJ, Raven, JA, Scheible, W-R, Teste, F, Veneklaas, EJ, Stitt, M & Lambers, H 2014, 'Low levels of ribosomal RNA partly account for the very high photosynthetic phosphorus-use efficiency of Proteaceae species.', Plant, Cell and Environment, vol. 37, no. 6, pp. 1276-1298.View/Download from: UTS OPUS or Publisher's site
Proteaceae species in south-western Australia occur on phosphorus- (P) impoverished soils. Their leaves contain very low P levels, but have relatively high rates of photosynthesis. We measured ribosomal RNA (rRNA) abundance, soluble protein, activities of several enzymes and glucose 6-phosphate (Glc6P) levels in expanding and mature leaves of six Proteaceae species in their natural habitat. The results were compared with those for Arabidopsis thaliana. Compared with A. thaliana, immature leaves of Proteaceae species contained very low levels of rRNA, especially plastidic rRNA. Proteaceae species showed slow development of the photosynthetic apparatus ('delayed greening'), with young leaves having very low levels of chlorophyll and Calvin-Benson cycle enzymes. In mature leaves, soluble protein and Calvin-Benson cycle enzyme activities were low, but Glc6P levels were similar to those in A. thaliana. We propose that low ribosome abundance contributes to the high P efficiency of these Proteaceae species in three ways: (1) less P is invested in ribosomes; (2) the rate of growth and, hence, demand for P is low; and (3) the especially low plastidic ribosome abundance in young leaves delays formation of the photosynthetic machinery, spreading investment of P in rRNA. Although Calvin-Benson cycle enzyme activities are low, Glc6P levels are maintained, allowing their effective use.
Fanesi, A, Raven, JA & Giordano, M 2014, 'Growth rate affects the responses of the green alga Tetraselmis suecica to external perturbations.', Plant, Cell and Environment, vol. 37, no. 2, pp. 512-519.View/Download from: UTS OPUS or Publisher's site
Acclimation to environmental changes involves a modification of the expressed proteome and metabolome. The reproductive advantage associated with the higher fitness that acclimation provides to the new conditions more than compensates for the costs of acclimation. To exploit such an advantage, however, the duration of the perturbation must be sufficiently long relative to the growth rate. Otherwise, a selective pressure may exist in favour of responses that minimize changes in carbon allocation and resource use and do not require reversal of the acclimation after the perturbation ceases (compositional homeostasis). We hypothesize that the choice between acclimation and homeostasis depends on the duration of the perturbation relative to the length of the cell cycle. To test this hypothesis, we cultured the green alga Tetraselmis suecica at two growth rates and subjected the cultures to three environmental perturbations. Carbon allocation was studied with Fourier transform infrared (FTIR) spectroscopy; elemental stoichiometry was investigated by total reflection X-ray fluorescence (TXRF) spectroscopy. Our data confirmed that growth rate is a crucial factor for C allocation in response to external changes, with a higher degree of compositional homeostasis in cells with lower growth rate.
Tamburic, B, Guruprasad, S, Radford, DT, Szabo, M, Lilley, R, Larkum, A, Franklin, J, Kramer, D, Blackburn, S, Raven, J, Schliep, MT & Ralph, PJ 2014, 'The effect of diel temperature and light cycles on the growth of Nannochloropsis oculata in a photobioreactor matrix', PLoS One, vol. 9, no. 1, p. e86047.View/Download from: UTS OPUS or Publisher's site
Szabo, M, Parker, KB, Guruprasad, S, Kuzhiumparambil, U, Lilley, RM, Tamburic, B, Schliep, MT, Larkum, A, Schreiber, U, Raven, J & Ralph, PJ 2014, 'Photosynthetic acclimation of Nannochloropsis oculata investigated by multi-wavelength chlorophyll fluorescence analysis', Bioresource Technology, vol. 167, pp. 521-529.View/Download from: UTS OPUS or Publisher's site
Multi-wavelength chlorophyll fluorescence analysis was utilised to examine the photosynthetic efficiency of the biofuel-producing alga Nannochloropsis oculata, grown under two light regimes; low (LL) and high (HL) irradiance levels. Wavelength dependency was evident in the functional absorption cross-section of Photosystem II (sII (?)), absolute electron transfer rates (ETR(II)), and non-photochemical quenching (NPQ) of chlorophyll fluorescence in both HL and LL cells. While sII(?) was not significantly different between the two growth conditions, HL cells upregulated ETR(II) 1.6 to 1.8-fold compared to LL cells, most significantly in the wavelength range of 440-540 nm. This indicates preferential utilisation of blue-green light, a highly relevant spectral region for visible light in algal pond conditions. Under these conditions, the HL cells accumulated saturated fatty acids, whereas polyunsaturated fatty acids were more abundant in LL cells. This knowledge is of importance for the use of N. oculata for fatty acid production in the biofuel industry.
Raven, J.A., Beardall, J., Larkum, A.W.D. & Sánchez-Baracaldo, P. 2013, 'Interactions of photosynthesis with genome size and function.', Philosophical transactions of the Royal Society of London. Series B, Biological sciences, vol. 368, no. 1622, p. 20120264.
Photolithotrophs are divided between those that use water as their electron donor (Cyanobacteria and the photosynthetic eukaryotes) and those that use a different electron donor (the anoxygenic photolithotrophs, all of them Bacteria). Photolithotrophs with the most reduced genomes have more genes than do the corresponding chemoorganotrophs, and the fastest-growing photolithotrophs have significantly lower specific growth rates than the fastest-growing chemoorganotrophs. Slower growth results from diversion of resources into the photosynthetic apparatus, which accounts for about half of the cell protein. There are inherent dangers in (especially oxygenic) photosynthesis, including the formation of reactive oxygen species (ROS) and blue light sensitivity of the water spitting apparatus. The extent to which photolithotrophs incur greater DNA damage and repair, and faster protein turnover with increased rRNA requirement, needs further investigation. A related source of environmental damage is ultraviolet B (UVB) radiation (280-320 nm), whose flux at the Earth's surface decreased as oxygen (and ozone) increased in the atmosphere. This oxygenation led to the requirements of defence against ROS, and decreasing availability to organisms of combined (non-dinitrogen) nitrogen and ferrous iron, and (indirectly) phosphorus, in the oxygenated biosphere. Differential codon usage in the genome and, especially, the proteome can lead to economies in the use of potentially growth-limiting elements.
O'Malley-James, JT, Greaves, JS, Raven, JA & Cockell, CS 2013, 'Swansong biospheres: Refuges for life and novel microbial biospheres on terrestrial planets near the end of their habitable lifetimes', International Journal of Astrobiology, vol. 12, no. 2, pp. 99-112.View/Download from: UTS OPUS or Publisher's site
The future biosphere on Earth (as with its past) will be made up predominantly of unicellular micro-organisms. Unicellular life was probably present for at least 2.5 Gyr before multicellular life appeared and will likely be the only form of life capable of surviving on the planet in the far future, when the ageing Sun causes environmental conditions to become more hostile to more complex forms of life. Therefore, it is statistically more likely that habitable Earth-like exoplanets we discover will be at a stage in their habitable lifetime more conducive to supporting unicellular, rather than multicellular life. The end stage of habitability on Earth is the focus of this work. A simple, latitude-based climate model incorporating eccentricity and obliquity variations is used as a guide to the temperature evolution of the Earth over the next 3 Gyr. This allows inferences to be made about potential refuges for life, particularly in mountains and cold-trap (ice) caves and what forms of life could live in these environments. Results suggest that in high latitude regions, unicellular life could persist for up to 2.8 Gyr from present. This begins to answer the question of how the habitability of Earth will evolve at local scales alongside the Sun's main sequence evolution and, by extension, how the habitability of Earth-like planets would evolve over time with their own host stars
Andrews, M, Raven, JA & Lea, PJ 2013, 'Do plants need nitrate? The mechanisms by which nitrogen form affects plants', ANNALS OF APPLIED BIOLOGY, vol. 163, no. 2, pp. 174-199.View/Download from: UTS OPUS or Publisher's site
Raven, J 2013, 'Polar auxin transport in relation to long-distance transport of nutrients in the Charales', Journal Of Experimental Botany, vol. 64, no. 1, pp. 1-9.View/Download from: UTS OPUS or Publisher's site
This paper examines the significance of the recent demonstration of polar auxin transport (PAT) in the green macroalga Chara (Charophyceae: Charales) and, especially, options for explaining some features of PAT in the Charales. The occurrence of PAT in the Charales shows that PAT originated in the algal ancestors of the embryophytes (liverworts, mosses, hornworts, and vascular plants), although it is not yet known if PAT occurs elsewhere in the Charophyceae or in other algae. While in the embryophytes PAT occurs in parenchymatously constructed structures which commonly also have xylem and phloem (or their bryophyte analogues) as long-distance transport processes in parallel to PAT, in Chara corallina PAT shares the pathway for long-distance transport of nutrients though the parenchymatously constructed nodal complexes and the single giant cells of the internode. The speed of auxin movement of PAT is much more rapid than that attributable to diffusion and of the same order as the rate of cytoplasmic streaming in the giant internodal cells, yet complete inhibition of streaming by the inhibitor cytochalasin H does not slow down auxin transport. Explanations for this phenomenon are sought in the operation of other mechanochemical motors, dyneinâtubulin and kinesinâtubulin, as alternatives to the myosinâactin system which powers cytoplasmic streaming. Experiments in which microtubules are disrupted, for example by colchicine, could show if one of the tubulin-based motors is involved. If these motors are involved, some mechanism is needed to amplify the speeds known for the motors to explain the order of magnitude higher speeds seen for auxin transport.
Raven, J, Beardall, J, Larkum, A & Sanchez-baracaldo, P 2013, 'Interactions of photosynthesis with genome size and function', Philosophical Transactions of the Royal Society B, vol. 368, no. 1622, pp. 1-11.View/Download from: UTS OPUS or Publisher's site
Photolithotrophs are divided between those that use water as their electron donor (Cyanobacteria and the photosynthetic eukaryotes) and those that use a different electron donor (the anoxygenic photolithotrophs, all of them Bacteria). Photolithotrophs wi
Lane, N, Martin, WF, Raven, JA & Allen, JF 2013, 'Energy, genes and evolution: introduction to an evolutionary synthesis', PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES, vol. 368, no. 1622.View/Download from: UTS OPUS or Publisher's site
Beardall, J & Raven, JA 2013, 'Calcification and ocean acidification: new insights from the coccolithophore Emiliania huxleyi', NEW PHYTOLOGIST, vol. 199, no. 1, pp. 1-3.View/Download from: Publisher's site
Fowler, D, Pyle, JA, Raven, JA & Sutton, MA 2013, 'The global nitrogen cycle in the twenty-first century: introduction', PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES, vol. 368, no. 1621.View/Download from: UTS OPUS or Publisher's site
Schmidt, S, Raven, JA & Paungfoo-Lonhienne, C 2013, 'The mixotrophic nature of photosynthetic plants', Functional Plant Biology, vol. 40, no. 5, pp. 425-438.View/Download from: UTS OPUS or Publisher's site
Plants typically have photosynthetically competent green shoots. To complement resources derived from the atmospheric environment, plants also acquire essential elements from soil. Inorganic ions and molecules are generally considered to be the sources of soil-derived nutrients, and plants tested in this respect can grow with only inorganic nutrients and so can live as autotrophs. However, mycorrhizal symbionts are known to access nutrients from organic matter. Furthermore, specialist lineages of terrestrial photosynthetically competent plants are mixotrophic, including species that obtain organic nutrition from animal prey (carnivores), fungal partners (mycoheterotrophs) or plant hosts (hemi-parasites). Although mixotrophy is deemed the exception in terrestrial plants, it is a common mode of nutrition in aquatic algae. There is mounting evidence that non-specialist plants acquire organic compounds as sources of nutrients, taking up and metabolising a range of organic monomers, oligomers, polymers and even microbes as sources of nitrogen and phosphorus. Plasma-membrane located transporter proteins facilitate the uptake of low-molecular mass organic compounds, endo-and phagocytosis may enable the acquisition of larger compounds, although this has not been confirmed. Identifying the mechanisms involved in the acquisition of organic nutrients will provide understanding of the ecological significance of mixotrophy. Here, we discuss mixotrophy in the context of nitrogen and phosphorus nutrition drawing parallels between algae and plants. © 2013 CSIRO.
Flynn, KJ, Stoecker, DK, Mitra, A, Raven, JA, Glibert, PM, Hansen, PJ, Graneli, E & Burkholder, JM 2013, 'Misuse of the phytoplanktonzooplankton dichotomy: the need to assign organisms as mixotrophs within plankton functional types', JOURNAL OF PLANKTON RESEARCH, vol. 35, no. 1, pp. 3-11.View/Download from: UTS OPUS or Publisher's site
Flynn, K.J., Blackford, J.C., Baird, M.E., Raven, J.A., Clark, D.R., Beardall, J., Brownlee, C., Fabian, H. & Wheeler, G.L. 2012, 'Erratum: Changes in pH at the exterior surface of plankton with ocean acidification (Nature Climate Change (2012) 2 (510-513))', Nature Climate Change, vol. 2, no. 10, p. 760.View/Download from: Publisher's site
O'Malley-James, J.T., Raven, J.A., Cockell, C.S. & Greaves, J.S. 2012, 'Life and Light: Exotic Photosynthesis in Binary and Multiple-Star Systems', ASTROBIOLOGY, vol. 12, no. 2, pp. 115-124.View/Download from: Publisher's site
O'Malley-James, JT, Raven, JA, Cockell, CS & Greaves, JS 2012, 'Life and light: Exotic photosynthesis in binary and multiple-star systems', Astrobiology, vol. 12, no. 2, pp. 115-124.View/Download from: UTS OPUS or Publisher's site
The potential for Earth-like planets within binary/multiple-star systems to host photosynthetic life was evaluated by modeling the levels of photosynthetically active radiation (PAR) such planets receive. Combinations of M and G stars in (i) close-binary systems; (ii) wide-binary systems, and (iii) three-star systems were investigated, and a range of stable radiation environments were found to be possible. These environmental conditions allow for the possibility of familiar, but also more exotic, forms of photosynthetic life, such as IR photosynthesizers and organisms that are specialized for specific spectral niches. © 2012, Mary Ann Liebert, Inc.
Flynn, KJ, Blackford, JC, Baird, ME, Raven, JA, Clark, DR, Beardall, J, Brownlee, C, Fabian, H & Wheeler, GL 2012, 'Changes in pH at the exterior surface of plankton with ocean acidification (vol 2, pg 510, 2012)', NATURE CLIMATE CHANGE, vol. 2, no. 10, pp. 760-760.
Raven, JA 2012, 'Effects on marine algae of changed seawater chemistry with increasing atmospheric CO2 (vol 111, pg 1, 2011)', BIOLOGY AND ENVIRONMENT-PROCEEDINGS OF THE ROYAL IRISH ACADEMY, vol. 112B, no. 3, pp. 315-315.
Raven, JA, Giordano, M, Beardall, J & Maberly, SC 2012, 'Algal evolution in relation to atmospheric CO2: carboxylases, carbon-concentrating mechanisms and carbon oxidation cycles', PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES, vol. 367, no. 1588, pp. 493-507.View/Download from: UTS OPUS or Publisher's site
Flynn, KJ, Blackford, JC, Baird, ME, Raven, J, Clark, DR, Beardall, J, Brownlee, C, Fabian, H & Wheeler, GL 2012, 'Changes in pH at the exterior surface of plankton with ocean acidification', Nature Climate Change, vol. 2, no. 7, pp. 510-513.View/Download from: UTS OPUS or Publisher's site
Anthropogenically released CO2 is dissolving in the ocean, causing a decrease in bulk-seawater pH (ocean acidification). Projections indicate that the pH will drop 0.3 units from its present value by 2100 (ref. 1). However, it is unclear how the growth of plankton is likely to respond. Using simulations we demonstrate how pH and carbonate chemistry at the exterior surface of marine organisms deviates increasingly from those of the bulk sea water as organism metabolic activity and size increases. These deviations will increase in the future as the buffering capacity of sea water decreases with decreased pH and as metabolic activity increases with raised seawater temperatures. We show that many marine plankton will experience pH conditions completely outside their recent historical range. However, ocean acidification is likely to have differing impacts on plankton physiology as taxon-specific differences in organism size, metabolic activity and growth rates during blooms result in very different microenvironments around the organism. This is an important consideration for future studies in ocean acidification as the carbonate chemistry experienced by most planktonic organisms will probably be considerably different from that measured in bulk-seawater samples. An understanding of these deviations will assist interpretation of the impacts of ocean acidification on plankton of different size and metabolic activity.
Veneklaas, EJ, Lambers, H, Bragg, J, Finnegan, PM, Lovelock, CE, Plaxton, WC, Price, CA, Scheible, W-R, Shane, MW, White, PJ & Raven, JA 2012, 'Opportunities for improving phosphorus-use efficiency in crop plants', NEW PHYTOLOGIST, vol. 195, no. 2, pp. 306-320.View/Download from: UTS OPUS or Publisher's site
Bragg, JG, Quigg, A, Raven, JA & Wagner, A 2012, 'Protein elemental sparing and codon usage bias are correlated among bacteria', MOLECULAR ECOLOGY, vol. 21, no. 10, pp. 2480-2487.View/Download from: UTS OPUS or Publisher's site
Raven, JA 2011, 'Effects on marine algae of changed seawater chemistry with increasing atmospheric CO2', Biology and Environment, vol. 111B, no. 1, pp. 1-17.View/Download from: UTS OPUS or Publisher's site
The acid-base relations of plant (including algal) environments are complex, comprising geological processes as modified by biology including, especially over the last 200 years, man. Some habitats (e.g. high intertidal rockpools and some freshwater bodies) have pH variations of up to three units over a diel cycle as a result of photosynthesis and respiration. Other habitats, e.g. nutrient-poor open ocean habitats, have diel variations that are more than an order of magnitude smaller. Anthropogenic influences on acid-base relations of different habitats include the input to the atmosphere of gases that dissolve to produce acidic solutions. The quantitatively predominant gas is CO 2 , but SO 2 , NO x and NH y (via nitrification) can also be significant. The influence of the acidic gases in aquatic habitats (including the upper layers of peat bogs) and on terrestrial photosynthetic organisms alters the inorganic carbon speciation and pH around the photosynthetic cells. The calcified coralline marine red macroalgae, with benthic and unattached (maerl) life forms, have extracellular calcification; their calcification rate will decline in the future, with a more CO 2 -rich ocean and decreasing CO 3 2- concentrations. The marine planktonic coccolithophores have intracellular calcification, though the coccoliths themselves occur externally. While many coccolithophores show decreased calcification with increasing external CO 2 and the attendant decrease in external CO 3 2- , this is not universal. For both coralline red algae and coccolithophores the external CaCO 3 will dissolve when seawater becomes undersaturated with respect to the relevant crystal form of CaCO 3 . Overall, the effects of increased CO 2 alone are negligible or result in increased growth of non-calcified algae, while there is most generally a decreased growth of calcified algae. © Royal Irish Academy.
Andrews, M, Edwards, GR, Ridgway, HJ, Cameron, KC, Di, HJ & Raven, JA 2011, 'Positive plant microbial interactions in perennial ryegrass dairy pasture systems', ANNALS OF APPLIED BIOLOGY, vol. 159, no. 1, pp. 79-92.View/Download from: Publisher's site
Hepburn, CD, Pritchard, DW, Cornwall, CE, McLeod, RJ, Beardall, J, Raven, JA & Hurd, CL 2011, 'Diversity of carbon use strategies in a kelp forest community: implications for a high CO2 ocean', GLOBAL CHANGE BIOLOGY, vol. 17, no. 7, pp. 2488-2497.View/Download from: UTS OPUS or Publisher's site
Raven, JA, Giordano, M, Beardall, J & Maberly, SC 2011, 'Algal and aquatic plant carbon concentrating mechanisms in relation to environmental change', PHOTOSYNTHESIS RESEARCH, vol. 109, no. 1-3, pp. 281-296.View/Download from: UTS OPUS or Publisher's site
Crawfurd, KJ, Raven, JA, Wheeler, GL, Baxter, EJ & Joint, I 2011, 'The Response of Thalassiosira pseudonana to Long-Term Exposure to Increased CO2 and Decreased pH', PLOS ONE, vol. 6, no. 10.View/Download from: UTS OPUS or Publisher's site
Marconi, M, Giordano, M & Raven, JA 2011, 'IMPACT OF TAXONOMY, GEOGRAPHY, AND DEPTH ON delta C-13 AND delta N-15 VARIATION IN A LARGE COLLECTION OF MACROALGAE', JOURNAL OF PHYCOLOGY, vol. 47, no. 5, pp. 1023-1035.View/Download from: UTS OPUS or Publisher's site
Lambers, H, Brundrett, MC, Raven, JA & Hopper, SD 2011, 'Plant mineral nutrition in ancient landscapes: high plant species diversity on infertile soils is linked to functional diversity for nutritional strategies', PLANT AND SOIL, vol. 348, no. 1-2, pp. 7-27.View/Download from: UTS OPUS or Publisher's site
Norici, A, Bazzoni, AM, Pugnetti, A, Raven, JA & Giordano, M 2011, 'Impact of irradiance on the C allocation in the coastal marine diatom Skeletonema marinoi Sarno and Zingone', PLANT CELL AND ENVIRONMENT, vol. 34, no. 10, pp. 1666-1677.View/Download from: UTS OPUS or Publisher's site
Raven, J & Thomas, H 2010, 'Grasses', CURRENT BIOLOGY, vol. 20, no. 19, pp. R837-R839.
Raven, JA 2010, 'Why are mycorrhizal fungi and symbiotic nitrogen-fixing bacteria not genetically integrated into plants?', ANNALS OF APPLIED BIOLOGY, vol. 157, no. 3, pp. 381-391.View/Download from: Publisher's site
Hodgson, JG, Sharafi, M, Jalili, A, Diaz, S, Montserrat-Marti, G, Palmer, C, Cerabolini, B, Pierce, S, Hamzehee, B, Asri, Y, Jamzad, Z, Wilson, P, Raven, JA, Band, SR, Basconcelo, S, Bogard, A, Carter, G, Charles, M, Castro-Diez, P, Cornelissen, JHC, Funes, G, Jones, G, Khoshnevis, M, Perez-Harguindeguy, N, Perez-Rontome, MC, Shirvany, FA, Vendramini, F, Yazdani, S, Abbas-Azimi, R, Boustani, S, Dehghan, M, Guerrero-Campo, J, Hynd, A, Kowsary, E, Kazemi-Saeed, F, Siavash, B, Villar-Salvador, P, Craigie, R, Naqinezhad, A, Romo-Diez, A, de Torres Espuny, L & Simmons, E 2010, 'Stomatal vs. genome size in angiosperms: the somatic tail wagging the genomic dog?', ANNALS OF BOTANY, vol. 105, no. 4, pp. 573-584.View/Download from: Publisher's site
Finkel, ZV, Beardall, J, Flynn, KJ, Quigg, A, Rees, TAV & Raven, JA 2010, 'Phytoplankton in a changing world: cell size and elemental stoichiometry', JOURNAL OF PLANKTON RESEARCH, vol. 32, no. 1, pp. 119-137.View/Download from: Publisher's site
Renberg, L, Johansson, AI, Shutova, T, Stenlund, H, Aksmann, A, Raven, JA, Gardestrom, P, Moritz, T & Samuelsson, G 2010, 'A Metabolomic Approach to Study Major Metabolite Changes during Acclimation to Limiting CO2 in Chlamydomonas reinhardtii', PLANT PHYSIOLOGY, vol. 154, no. 1, pp. 187-196.View/Download from: Publisher's site
Lambers, H, Brundrett, MC, Raven, JA & Hopper, SD 2010, 'Plant mineral nutrition in ancient landscapes: high plant species diversity on infertile soils is linked to functional diversity for nutritional strategies', PLANT AND SOIL, vol. 334, no. 1-2, pp. 11-31.View/Download from: UTS OPUS or Publisher's site
Titlyanov, EA, Kiyashko, SI, Titlyanova, TV & Raven, JA 2010, 'delta C-13 and delta N-15 in tissue of coral polyps and epilithic algae inhabiting damaged coral colonies under the influence of different light intensities', AQUATIC ECOLOGY, vol. 44, no. 1, pp. 13-21.View/Download from: Publisher's site
Flynn, KJ, Raven, JA, Rees, TAV, Finkel, Z, Quigg, A & Beardall, J 2010, 'IS THE GROWTH RATE HYPOTHESIS APPLICABLE TO MICROALGAE?', JOURNAL OF PHYCOLOGY, vol. 46, no. 1, pp. 1-12.View/Download from: Publisher's site
Cockell, CS, Kaltenegger, L & Raven, JA 2009, 'Cryptic Photosynthesis-Extrasolar Planetary Oxygen Without a Surface Biological Signature', ASTROBIOLOGY, vol. 9, no. 7, pp. 623-636.View/Download from: UTS OPUS or Publisher's site
Cockell, CS, Leger, A, Fridlund, M, Herbst, TM, Kaltenegger, L, Absil, O, Beichman, C, Benz, W, Blanc, M, Brack, A, Chelli, A, Colangeli, L, Cottin, H, du Foresto, FC, Danchi, WC, Defrere, D, den Herder, J-W, Eiroa, C, Greaves, J, Henning, T, Johnston, KJ, Jones, H, Labadie, L, Lammer, H, Launhardt, R, Lawson, P, Lay, OP, LeDuigou, J-M, Liseau, R, Malbet, F, Martin, SR, Mawet, D, Mourard, D, Moutou, C, Mugnier, LM, Ollivier, M, Paresce, F, Quirrenbach, A, Rabbia, YD, Raven, JA, Rottgering, HJA, Rouan, D, Santos, NC, Selsis, F, Serabyn, E, Shibai, H, Tamura, M, Thiebaut, E, Westall, F & White, GJ 2009, 'Darwin-A Mission to Detect and Search for Life on Extrasolar Planets', ASTROBIOLOGY, vol. 9, no. 1, pp. 1-22.View/Download from: UTS OPUS or Publisher's site
Andrews, M, Lea, PJ, Raven, JA & Azevedo, RA 2009, 'Nitrogen use efficiency. 3. Nitrogen fixation: genes and costs', ANNALS OF APPLIED BIOLOGY, vol. 155, no. 1, pp. 1-13.View/Download from: Publisher's site
Raven, JA & Giordano, M 2009, 'Biomineralization by photosynthetic organisms: Evidence of coevolution of the organisms and their environment?', GEOBIOLOGY, vol. 7, no. 2, pp. 140-154.View/Download from: Publisher's site
Dimier, C, Brunet, C, Geider, R & Raven, J 2009, 'Growth and photoregulation dynamics of the picoeukaryote Pelagomonas calceolata in fluctuating light', LIMNOLOGY AND OCEANOGRAPHY, vol. 54, no. 3, pp. 823-836.View/Download from: Publisher's site
Raven, JA, Beardall, J, Flynn, KJ & Maberly, SC 2009, 'Phagotrophy in the origins of photosynthesis in eukaryotes and as a complementary mode of nutrition in phototrophs: relation to Darwin's insectivorous plants', JOURNAL OF EXPERIMENTAL BOTANY, vol. 60, no. 14, pp. 3975-3987.View/Download from: Publisher's site
Wouters, J, Raven, JA, Minnhagen, S & Janson, S 2009, 'The luggage hypothesis: Comparisons of two phototrophic hosts with nitrogen-fixing cyanobacteria and implications for analogous life strategies for kleptoplastids/secondary symbiosis in dinoflagellates', SYMBIOSIS, vol. 49, no. 2, pp. 61-70.View/Download from: Publisher's site
Woodward, FI, Bardgett, RD, Raven, JA & Hetherington, AM 2009, 'Biological Approaches to Global Environment Change Mitigation and Remediation', CURRENT BIOLOGY, vol. 19, no. 14, pp. R615-R623.View/Download from: Publisher's site
Hurd, CL, Hepburn, CD, Currie, KI, Raven, JA & Hunter, KA 2009, 'TESTING THE EFFECTS OF OCEAN ACIDIFICATION ON ALGAL METABOLISM: CONSIDERATIONS FOR EXPERIMENTAL DESIGNS', JOURNAL OF PHYCOLOGY, vol. 45, no. 6, pp. 1236-1251.View/Download from: Publisher's site
Granum, E, Roberts, K, Raven, JA & Leegood, RC 2009, 'PRIMARY CARBON AND NITROGEN METABOLIC GENE EXPRESSION IN THE DIATOM THALASSIOSIRA PSEUDONANA (BACILLARIOPHYCEAE): DIEL PERIODICITY AND EFFECTS OF INORGANIC CARBON AND NITROGEN', JOURNAL OF PHYCOLOGY, vol. 45, no. 5, pp. 1083-1092.View/Download from: Publisher's site
Wouters, J, Raven, JA, Minnhagen, S & Janson, S 2009, 'The luggage hypothesis: Comparisons of two phototrophic hosts with nitrogen-fixing cyanobacteria and implications for analogous life strategies for kleptoplastids/secondary symbiosis in dinoflagellates', Symbiosis, vol. 49, no. 3, pp. 61-70.View/Download from: Publisher's site
Nostoc and Richelia belong to a group of heterocystous cyanobacteria and are unique within this group in forming intracellular symbioses with phototrophic hosts, the angiosperm Gunnera and the diatoms (algae) Rhizosolenia and Hemiaulus, respectively. The function of the cyanobiont is similar in the symbioses, namely providing fixed atmospheric nitrogen to their hosts; also the cyanobionts are contained in a host compartment, the symbiosome. The evolutionary timescale for the cyanobiont-endosymbiosis formation is in both instances about 90 Ma. However, the potentials for further co-evolution of host and microsymbiont, are different. Nostoc is regarded as preyed upon by its host, while in the Richelia-Rhizosolenia symbiosis example the evolution towards a new type of permanent organelle is possible. It is proposed that symbiosis is ruled by divergent host strategies. In the case of Richelia-Rhizosolenia the evolution of a permanent symbiosis is linked to diatom hosts needing to carry the cyanobiont permanently, as it is not available free-living in the oceans. However, in the case of Nostoc/Gunnera, the host exploits an abundant cyanobacterial species. A model where the relative abundance of microsymbionts determines the nature of the symbiosis comes into view: If environmental ratios of host/microsymbiont are so that hosts are the dominating party, then the host has to carry the microsymbiont as luggage (vertical transmission). Likewise, if the ratio of microsymbiont is higher than host, than the host will prey on the microsymbiont (horizontal transmission). The article also discusses the retention of secondary plastids in dinoflagellates. We show that dinoflagellates are organisms that exemplify both types of strategies that is either preying or harbouring a permanent organelle. The difference from the cyanobacterial example is that only parts of the eukaryotic microsymbionts are kept, usually only the plastid. We emphasize that the dinoflagellates can obtain th...
Raven, JA 2009, 'Functional evolution of photochemical energy transformations in oxygen-producing organisms', Functional Plant Biology, vol. 36, no. 6, pp. 505-515.View/Download from: Publisher's site
Chlorophyll a is the photochemical agent accounting for most oxygenic photosynthesis, that is, over 99.9% of photosynthetic primary activity on Earth. The spectral and energetic properties of chlorophyll a can, at least in part, be rationalised in terms of the solar spectral output and the energetics of oxygen production and carbon dioxide reduction with two photochemical reactions. The long wavelength limit on in vivo chlorophyll a absorption is probably close to the energetic limit: longer wavelengths could not support a high rate and efficiency of oxygenic photosynthesis. Retinal, a -carotene derivative that is the chromophore of rhodopsin, acts not only as a sensory pigment, but also as an ion-pumping photochemical transducer. Both sensory and energy-transforming rhodopsins occur in oxygenic phototrophs, although the extent of expression and the function of the latter are not well understood. © 2009 CSIRO.
Cockell, CS, Raven, JA, Kaltenegger, L & Logan, RC 2009, 'Planetary targets in the search for extrasolar oxygenic photosynthesis', Plant Ecology and Diversity, vol. 2, no. 2, pp. 207-219.View/Download from: Publisher's site
Background: In the coming decades space telescopes will be constructed that will attempt to find the gaseous products of oxygenic photosynthesis, the most promising biosignatures of life, in the atmospheres of temperate Earth-like planets orbiting distant stars. Aims: This paper aims to provide a synthesis of the range of feasible targets either planets or their satellites that could harbour photosynthesis. Methods: We calculated photosynthetically active radiation (PAR) fluxes on a diversity of planetary bodies including those receiving direct light from a single star, similarly to the Earth, and investigated the potential of these fluxes to support photosynthesis. Results: All main sequence stars emit radiation that is capable of supporting photosynthesis on Earth-like planets. We discuss tidally-locked M star planets as a special case. Less conventional targets for searches include large moons orbiting gas giant planets, which receive reflected light from their host planets and from the host star, planets in stable orbits in binary star systems, and the search for two planets within the same star system with photosynthetic signatures. Conclusions: A diversity of planetary bodies are targets in the search for extrasolar photosynthesis. The demonstration that many or none of these candidate planetary bodies harbour photosynthesis would be an important conclusion in understanding the evolution and prevalence of photosynthesis. © 2009 Botanical Society of Scotland and Taylor & Francis.
Beardall, J, Allen, D, Bragg, J, Finkel, ZV, Flynn, KJ, Quigg, A, Rees, TAV, Richardson, A & Raven, JA 2009, 'Allometry and stoichiometry of unicellular, colonial and multicellular phytoplankton', NEW PHYTOLOGIST, vol. 181, no. 2, pp. 295-309.View/Download from: Publisher's site
Raven, J 2008, 'The institutional logic of welfare attitudes: How welfare regimes influence public support', JOURNAL OF EUROPEAN SOCIAL POLICY, vol. 18, no. 2, pp. 205-205.View/Download from: Publisher's site
Jones, MR, Raven, JA, Leith, ID, Cape, JN, Smith, RI & Fowler, D 2008, 'Short-term flux chamber experiment to quantify the deposition of gaseous N-15-NH3 to Calluna vulgaris', AGRICULTURAL AND FOREST METEOROLOGY, vol. 148, no. 6-7, pp. 893-901.View/Download from: Publisher's site
Kilminster, KL, Walker, DI, Thompson, PA & Raven, JA 2008, 'Changes in growth, internode distance and nutrient concentrations of the seagrass Halophila ovalis with exposure to sediment sulphice', MARINE ECOLOGY PROGRESS SERIES, vol. 361, pp. 83-91.View/Download from: Publisher's site
Raven, JA, Cockell, CS & De La Rocha, CL 2008, 'The evolution of inorganic carbon concentrating mechanisms in photosynthesis', PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES, vol. 363, no. 1504, pp. 2641-2650.View/Download from: Publisher's site
Raven, JA, Giordano, M & Beardall, J 2008, 'Insights into the evolution of CCMs from comparisons with other resource acquisition and assimilation processes', PHYSIOLOGIA PLANTARUM, vol. 133, no. 1, pp. 4-14.View/Download from: Publisher's site
Titlyanov, EA, Kiyashko, SI, Titlyanova, TV, Kalita, TL & Raven, JA 2008, 'delta(13)C and delta(15)N values in reef corals Porites lutea and P-cylindrica and in their epilithic and endolithic algae', MARINE BIOLOGY, vol. 155, no. 4, pp. 353-361.View/Download from: Publisher's site
Iglesias-Rodriguez, MD, Buitenhuis, ET, Raven, JA, Schofield, O, Poulton, AJ, Gibbs, S, Halloran, PR & de Baar, HJW 2008, 'Response to Comment on "Phytoplankton Calcification in a High-CO2 World"', SCIENCE, vol. 322, no. 5907.View/Download from: Publisher's site
Lambers, H, Raven, JA, Shaver, GR & Smith, SE 2008, 'Plant nutrient-acquisition strategies change with soil age', TRENDS IN ECOLOGY & EVOLUTION, vol. 23, no. 2, pp. 95-103.View/Download from: Publisher's site
Kuehn, SF & Raven, JA 2008, 'Photosynthetic oscillation in individual cells of the marine diatom Coscinodiscus wailesii (Bacillariophyceae) revealed by microsensor measurements', PHOTOSYNTHESIS RESEARCH, vol. 95, no. 1, pp. 37-44.View/Download from: Publisher's site
Raven, J 2007, 'Why do phytoplankton make such a Fuss about carbon dioxide?', JOURNAL OF PHYCOLOGY, vol. 43, pp. 54-55.
Jones, MR, Leith, ID, Fowler, D, Raven, JA, Sutton, MA, Nemitz, E, Cape, JN, Sheppard, LJ, Smith, RI & Theobald, MR 2007, 'Concentration-dependent NH3 deposition processes for mixed moorland semi-natural vegetation', ATMOSPHERIC ENVIRONMENT, vol. 41, no. 10, pp. 2049-2060.View/Download from: Publisher's site
Raven, JA & Larkum, AWD 2007, 'Are there ecological implications for the proposed energetic restrictions on photosynthetic oxygen evolution at high oxygen concentrations?', PHOTOSYNTHESIS RESEARCH, vol. 94, no. 1, pp. 31-42.View/Download from: Publisher's site
Leegood, R, Roberts, K, Granum, E & Raven, J 2007, 'Single-cell C-4 photosynthesis in marine diatoms?', PHOTOSYNTHESIS RESEARCH, vol. 91, no. 2-3, pp. 222-223.
Andrews, M, Scholefield, D, Abberton, MT, McKenzie, BA, Hodge, S & Raven, JA 2007, 'Use of white clover as an alternative to nitrogen fertiliser for dairy pastures in nitrate vulnerable zones in the UK: productivity, environmental impact and economic considerations', ANNALS OF APPLIED BIOLOGY, vol. 151, no. 1, pp. 11-23.View/Download from: Publisher's site
Jones, MR, Leith, ID, Raven, JA, Fowler, D, Sutton, MA, Nemitz, E, Cape, JN, Sheppard, LJ & Smith, RI 2007, 'Concentration-dependent NH3 deposition processes for moorland plant species with and without stomata', ATMOSPHERIC ENVIRONMENT, vol. 41, no. 39, pp. 8980-8994.View/Download from: Publisher's site
Raven, J, Beardall, J, Franklin, L & Giordano, M 2007, 'Influence of nutrient supply and UV on photosynthesis and inorganic carbon concentrating mechanisms: relation to environmental change?', PHOTOSYNTHESIS RESEARCH, vol. 91, no. 2-3, pp. 297-297.
Roberts, K, Granum, E, Leegood, RC & Raven, JA 2007, 'C-3 and C-4 pathways of photosynthetic carbon assimilation in marine diatoms are under genetic, not environmental, control', PLANT PHYSIOLOGY, vol. 145, no. 1, pp. 230-235.View/Download from: Publisher's site
Andrews, M, Raven, JA, Sprent, JI & Lea, PJ 2007, 'Is shoot growth correlated to leaf protein concentration?', Trends in plant science, vol. 12, no. 12, pp. 531-532.View/Download from: Publisher's site
Andrews, M, Scholefield, D, Abberton, MT, McKenzie, BA, Hodge, S & Raven, JA 2007, 'Use of white clover as an alternative to nitrogen fertiliser for dairy pastures in nitrate vulnerable zones in the UK: Productivity, environmental impact and economic considerations', Annals of Applied Biology, vol. 151, no. 1, pp. 11-23.View/Download from: Publisher's site
Perennial ryegrass and perennial ryegrass/white clover permanent dairy pastures are compared with respect to productivity, environmental impact and financial costs in nitrate vulnerable zones (NVZ) in the UK. With appropriate management, and utilisation of recommended perennial ryegrass and white clover cultivars, white clover is likely to stabilise at around 20% of total dry matter production in a mixed pasture. Plant dry matter production and milk production from a perennial ryegrass/white clover pasture are likely to be similar to that from a perennial ryegrass pasture receiving 200 kg N ha -1 annum -1 and around 70% of that obtained with perennial ryegrass supplied with 350-400 kg N ha -1 annum -1 . Nitrate, phosphorus and methane losses from the system and decreases in biodiversity relative to a grazed indigenous sward are likely to be similar for a perennial ryegrass/white clover pasture and a perennial ryegrass pasture receiving 200 kg N ha -1 annum -1 : nitrate leachate from both systems is likely to comply with European legislation. Greenhouse gas emissions resulting from nitrogen (N) fertiliser production would be avoided with the perennial ryegrass/white clover pasture. Within NVZ stocking rate restrictions, white clover can provide the N required by a pasture at a lower financial cost than that incurred by the application of N fertiliser. © 2007 Association of Applied Biologists.
Cockell, CS & Raven, JA 2007, 'Ozone and life on the Archaean earth', PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES, vol. 365, no. 1856, pp. 1889-1901.View/Download from: Publisher's site
Giordano, M, Norici, A, Gilmour, DJ & Raven, JA 2007, 'Physiological responses of the green alga Dunaliella parva (Volvocales, Chlorophyta) to controlled incremental changes in the N source', Functional Plant Biology, vol. 34, no. 10, pp. 925-934.View/Download from: Publisher's site
This work is aimed at obtaining information on the acclimation processes of the green flagellate Dunaliella parva Lerche to gradual changes in the N source from NO3- to NH4+, in continuous cultures. Photosynthesis, dark respiration, and light-independent carbon fixation (LICF) rates, chlorophyll a fluorescence, RUBISCO and phosphoenolpyruvate carboxylase (PEPc) activities, plasmalemma electrical potential difference, cell volume, and absolute or relative amounts of major cell constituents were measured. Two phases characterised the response to the transition from NO3- to NH4+: (1) an initial phase in which photosynthesis and anaplerosis were stimulated and protein increased; (2) a subsequent phase in which most parameters reached new values that were close to those at the beginning of the experiment (100% NO 3-). The only exceptions were PEPc activity and LICF, whose rates remained at least 2-fold higher than at 100% NO3-, when NH4+ was the sole N source. The results are indicative of a tendency to re-establish homeostasis, after an initial perturbation of the intracellular composition. The roles of different metabolic processes during acclimation are discussed. © CSIRO 2007.
Beerling, DJ, Hewitt, CN, Pyle, JA & Raven, JA 2007, 'Critical issues in trace gas biogeochemistry and global change', PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES, vol. 365, no. 1856, pp. 1629-1642.View/Download from: Publisher's site
Jones, MR, Leith, ID, Fowler, D, Raven, JA, Sutton, MA, Nemitz, E, Cape, JN, Sheppard, LJ, Smith, RI & Theobald, MR 2007, 'Concentration-dependent NH3 deposition processes for mixed moorland semi-natural vegetation', Atmospheric Environment, vol. 41, no. 10, pp. 2049-2060.View/Download from: Publisher's site
Dry deposition modelling typically assumes that canopy resistance (Rc) is independent of ammonia (NH3) concentration. An innovative flux chamber system was used to provide accurate continuous measurements of NH3 deposition to a moorland composed of a mixture of Calluna vulgaris (L.) Hull, Eriophorum vaginatum L. and Sphagnum spp. Ammonia was applied at a wide range of concentrations (1-100 g m-3). The physical and environmental properties and the testing of the chamber are described, as well as results for the moorland vegetation using the 'canopy resistance' and 'canopy compensation point' interpretations of the data. Results for moorland plant species demonstrate that NH3 concentration directly affects the rate of NH3 deposition to the vegetation canopy, with Rc and cuticular resistance (Rw) increasing with increasing NH3 concentrations. Differences in Rc were found between night and day: during the night Rc increases from 17 s m-1 at 10 g m-3 to 95 s m-1 at 80 g m-3, whereas during the day Rc increases from 17 s m-1 at 10 g m-3 to 48 s m-1 at 80 g m-3. The lower resistance during the day is caused by the stomata being open and available as a deposition route to the plant. Rw increased with increasing NH3 concentrations and was not significantly different between day and night (at 80 g m-3 NH3 day Rw=88 s m-1 and night Rw=95 s m-1). The results demonstrate that assessments using fixed Rc will over-estimate NH3 deposition at high concentrations (over 15 g m-3). © 2006 Elsevier Ltd. All rights reserved.
Theobald, S, Raven, J, Tolhurst, R, Makwiza, I & Taegtmeyer, M 2006, 'Public health approach to HIV treatment in resource-poor settings.', Lancet (London, England), vol. 368, no. 9541, p. 1064.View/Download from: Publisher's site
Leegood, R, Granum, E, Brown, K & Raven, J 2006, 'Single-cell C4 photosynthesis in marine diatoms?', COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY A-MOLECULAR & INTEGRATIVE PHYSIOLOGY, vol. 143, no. 4, pp. S160-S161.
Finkel, ZV, Quigg, A, Raven, JA, Reinfelder, JR, Schofield, OE & Falkowski, PG 2006, 'Irradiance and the elemental stoichiometry of marine phytoplankton', LIMNOLOGY AND OCEANOGRAPHY, vol. 51, no. 6, pp. 2690-2701.View/Download from: Publisher's site
Kilminster, KL, Walker, DI, Thompson, PA & Raven, JA 2006, 'Limited nutritional benefit to the seagrass Halophila ovalis, in culture, following sediment organic matter enrichment', ESTUARINE COASTAL AND SHELF SCIENCE, vol. 68, no. 3-4, pp. 675-685.View/Download from: Publisher's site
Raven, JA & Cockell, CS 2006, 'Influence on photosynthesis of starlight, moonlight, planetlight, and light pollution (reflections on photosynthetically active radiation in the universe)', ASTROBIOLOGY, vol. 6, no. 4, pp. 668-675.View/Download from: Publisher's site
Enzymes and transporters that catalyse reactions involving inorganic carbon are well characterized with respect to the species of inorganic carbon (CO2 or HCO3-) with which they interact. There is less information on the species recognized by proteins that sense inorganic carbon. In this issue of the Biochemical Journal, Hammer and colleagues show conclusively that cyanobacterial adenylyl cyclases are activated by CO2 and not HCO3-, as was believed previously. While in some circumstances a similar in vivo regulatory outcome is achieved from sensing HCO3- as from sensing CO2, there are cases in which the outcomes are significantly different. The most striking example is where a compartment lacks carbonic anhydrase yet supports large metabolic fluxes of inorganic carbon species so that CO2 and HCO3- are not at equilibrium. Other examples involve changes in pH, or temperature, of a compartment containing an equilibrium mixture of CO2 and HCO3-.
Montechiaro, F, Hirschmugl, CJ, Raven, JA & Giordano, M 2006, 'Homeostasis of cell composition during prolonged darkness.', Plant, cell & environment, vol. 29, no. 12, pp. 2198-2204.View/Download from: Publisher's site
The chemical composition of organisms in relation to their environmental resource availability is an area of intense research activity. We studied the changes in cell composition of the cyanobacterium Phormidium autumnale in response to prolonged darkness. Cells allocated their internal resources in a homeostatic manner, oxidizing all the three major cellular constituents in a proportional way. This resulted in constant C/N and carbohydrates, lipids and proteins ratios that remained unaltered throughout the whole incubation period. We propose the maintenance of balanced cell composition (homeostasis) as an evolutionary strategy related to environmental transitory changes.
Andrews, M, Raven, JA, Lea, PJ & Sprent, JI 2006, 'A role for shoot protein in shoot-root dry matter allocation in higher plants', ANNALS OF BOTANY, vol. 97, no. 1, pp. 3-10.View/Download from: Publisher's site
Quigg, A, Kevekordes, K, Raven, JA & Beardall, J 2006, 'Limitations on microalgal growth at very low photon fluence rates: the role of energy slippage.', Photosynthesis research, vol. 88, no. 3, pp. 299-310.View/Download from: Publisher's site
The lower limits of photosynthetically useable radiation at which growth and photosynthesis can occur establish the lower boundaries for the extent of photolithotrophy in the biosphere. Photolithotrophic growth denotes the capacity to grow with photons as the sole energy input. Slippage in terms of photosynthetic energy conversion implies a less than theoretical stoichiometry of energy-transduction process(es) such as the dissipation of intermediates of O(2) evolution and of ATP synthesis (H(+)/e(-) and H(+)/ATP ratios). Slippage is particularly important in limiting the growth of photolithotrophic organisms at very low photon fluence rates. We found that Dunaliella tertiolecta and Phaeodactylum tricornutum avoid such reductions in photon use efficiency by increasing the size and number of their photosynthetic units, respectively, and by altering Q(A) reduction kinetics on the reducing side of PS II. P. tricornutum is also less susceptible to slippage in terms of the breakdown of intermediates in its O(2) evolution pathway than D. tertiolecta. Minimizing H(+) leakage through the CF(0)-CF(1) ATP synthetase (and other H(+ )porters) is also discussed briefly. In combination, strategies employed by P. tricornutum effectively allow it to grow and photosynthesize at lower rates of energy input than D. tertiolecta, consistent with our observations. Differences in the responses of the photosynthetic apparatus of these two marine microalgae are mechanistic and probably representative of evolutionary divergences associated with strategies for dealing with environmental perturbations.
Kevekordes, K, Holland, D, Häubner, N, Jenkins, S, Koss, R, Roberts, S, Raven, JA, Scrimgeour, CM, Shelly, K, Stojkovic, S & Beardall, J 2006, 'Inorganic carbon acquisition by eight species of Caulerpa (Caulerpaceae, Chlorophyta)', Phycologia, vol. 45, no. 4, pp. 442-449.View/Download from: Publisher's site
This investigation examines the occurrence of carbon concentrating mechanisms (CCMs) in eight species of the acellular green marine macroalgal genus Caulerpa. The measurements made were of the 13C of organic matter, extracellular carbonic anhydrase activities, pH compensation values, and the inorganic C dependence of light-saturated photosynthesis rates. The data suggest that the pyrenoid-containing C. cactoides and C. geminata, and probably C. scalpelliformis (which lacks pyrenoids) have CCMs. Net diffusive influx of CO2 fulfills the inorganic carbon requirements of the other species for which pH-drift data are available, i.e. C. flexilis, C. longifolia, C. obscura and C. brownii. No pH drift data are available for C. trifaria and no information is available as to whether it has pyrenoids, although 13C data suggest the absence of a CCM in this species. The three species showing evidence of CCMs have the lowest affinities for inorganic C of the eight species tested. This apparently paradoxical finding has precedence for marine red-macroalgae, and requires that the selective significance of the CCMs in these organisms is not that of increased inorganic C affinity, but is perhaps associated with the ability to both suppress photoinhibition and to photosynthesize at higher seawater pH values.
Granum, E, Leegood, RC, Brown, K & Raven, JA 2005, 'SINGLE-CELL C(4) PHOTOSYNTHESIS IN MARINE DIATOMS?', PHYCOLOGIA, vol. 44, no. 4, pp. 38-39.
Granum, E, Leegood, RC, Brown, K & Raven, JA 2005, 'The role of the C-4 pathway in carbon acquisition by marine diatoms', COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY A-MOLECULAR & INTEGRATIVE PHYSIOLOGY, vol. 141, no. 3, pp. S284-S284.
Raven, JA, Andrews, M & Quigg, A 2005, 'The evolution of oligotrophy: implications for the breeding of crop plants for low input agricultural systems', ANNALS OF APPLIED BIOLOGY, vol. 146, no. 3, pp. 261-280.View/Download from: Publisher's site
Raven, JA, Finkel, ZV & Irwin, AJ 2005, 'Picophytoplankton: Bottom-up and top-down controls on ecology and evolution', VIE ET MILIEU-LIFE AND ENVIRONMENT, vol. 55, no. 3-4, pp. 209-215.
Andrews, M, Maule, HG, Raven, JA & Mistry, A 2005, 'Extension growth of Impatiens glandulifera at low irradiance: Importance of nitrate and potassium accumulation', Annals of Botany, vol. 95, no. 4, pp. 641-648.View/Download from: Publisher's site
* Background and Aims: The summer annual Impatiens glandulifera can reach 3 m in height within deciduous woodland. The primary objective was to determine if NO3- accumulation, and hence its osmotic effect, is an important physiological mechanism allowing Impatiens to achieve substantial height under low irradiance. * Methods: Stem extension, concentrations of K+ and NO3- in leaves and concentrations of K+, NO3- and other inorganic anions, malate, sugars, total N and total osmoticum in stem were measured in I. glandulifera sampled at different irradiance levels in deciduous woodland and in a glasshouse. Also, the energetic costs, as absorbed photons, of generating osmolarity in stem cell vacuoles with KNO3, K2malate or hexose sugar were determined. * Key Results: Results were similar in the woodland and glasshouse. At 50-100 % relative irradiance (Ir; open ground PAR = 100 % Ir) and 2-10 % Ir, plant height increased from 7-14 cm to 130-154 cm in 64-67 d. Leaf and stem NO3- concentrations were negligible at 50-100 % Ir while K+, malate2- and sugars, respectively, accounted for 33.2-50.1 %, 19.3-20.8 % and 2.0-2.6 % of total osmoticum in stems. At 2-10 % Ir, NO3- concentrations were four to eight times greater in stems than leaves. Here, NO3- constituted 26.7-34.3 % of the total osmotic concentration in the stem and NO3--N constituted 69-81 % of total N in stem tissue. Also at 2-10 % Ir, K+ comprised 44.9-45.9 % and malate plus sugars 2.2-3.1 % of total osmotic concentration. The energy cost of osmoticum as KNO3 was calculated as less than half that of malate and less than one-seventh that for hexose. Further calculations suggest that use of KNO 3, K2malate or glucose as osmoticum at low irradiance would, respectively, cost approx. 7 %, 16 % and 50 % of the total construction cost of the stem. * Conclusions: It is concluded that accumulation of NO3- in place of organic molecules in stems is an important mechanism allowing I. glandulifera to achieve substantial heigh...
Raven, JA, Handley, LL & Andrews, M 2004, 'Global aspects of C/N interactions determining plant-environment interactions', JOURNAL OF EXPERIMENTAL BOTANY, vol. 55, no. 394, pp. 11-25.View/Download from: Publisher's site
Ultraviolet radiation is more damaging on the surface of Mars than on Earth because of the lack of an ozone shield. We investigated micro-habitats in which UV radiation could be reduced to levels similar to those found on the surface of present-day Earth, but where light in the photosynthetically active region (400-700 nm) would be above the minimum required for photosynthesis. We used a simple radiative transfer model to study four micro-habitats in which such a theoretical Martian Earth-like Photosynthetic Zone (MEPZ) might exist. A favorable radiation environment was found in martian soils containing iron, encrustations of halite, polar snows and crystalline rocks shocked by asteroid or comet impacts, all of which are known habitats for phototrophs on Earth. Although liquid water and nutrients are also required for life, micro-environments with favorable radiation environments for phototrophic life exist in a diversity of materials on Mars. This finding suggests that the lack of an ozone shield is not in itself a limit to the biogeographically widespread colonization of land by photosynthetic organisms, even if there are no other UV-absorbers in the atmosphere apart from carbon dioxide. When applied to the Archean Earth, these data suggest that even with the worst-case assumptions about the UV radiation environment, early land masses could have been colonized by primitive photosynthetic organisms. Such zones could similarly exist on anoxic extra-solar planets lacking ozone shields. © 2004 Elsevier Inc. All rights reserved.
Beardall, J & Raven, JA 2004, 'The potential effects of global climate change on microalgal photosynthesis, growth and ecology', PHYCOLOGIA, vol. 43, no. 1, pp. 26-40.View/Download from: Publisher's site
Falkowski, PG, Katz, ME, Knoll, AH, Quigg, A, Raven, JA, Schofield, O & Taylor, FJR 2004, 'The evolution of modern eukaryotic phytoplankton', SCIENCE, vol. 305, no. 5682, pp. 354-360.View/Download from: Publisher's site
Andrews, M, Lea, PJ, Raven, JA & Lindsey, K 2004, 'Can genetic manipulation of plant nitrogen assimilation enzymes result in increased crop yield and greater N-use efficiency? An assessment', ANNALS OF APPLIED BIOLOGY, vol. 145, no. 1, pp. 25-40.View/Download from: Publisher's site
Cooke, RRM, Hurd, CL, Lord, JM, Peake, BM, Raven, JA & Rees, TAV 2004, 'Iron and zinc content of Hormosira banksii in New Zealand', New Zealand Journal of Marine and Freshwater Research, vol. 38, no. 1, pp. 73-85.View/Download from: Publisher's site
In the Northern Hemisphere, brown seaweeds in the Order Fucales have been used extensively as bio-monitors of heavy metal contamination in sea water, but in New Zealand there has been no assessment of the suitability of the Fucales in this role. We measured iron (Fe) and zinc (Zn) concentrations in the intertidal fucalean seaweed Hormosira banksii at three sites in Otago, southeastern New Zealand and two sites at Leigh, northeastern New Zealand. There was no evidence of Zn or Fe contamination at any site studied. Zn levels for H. banksii from Otago Harbour followed a trend similar to an earlier study of Ulva sp. and the Fe content reflected patterns previously observed in sea water. Thus, as for Northern Hemisphere fucalean seaweeds, H. banksii is potentially useful as a biomonitor for heavy metals in sea water. Levels of Fe and Zn were among the lowest of any brown seaweed worldwide, and the Fe content of H. banksii from Waterfall Reef, Goat Island Marine Reserve, Leigh, was 50% lower than samples from Otago. These low trace metal levels led us to examine if the growth of H. banksii in New Zealand is limited by Fe or Zn. The physiological requirements of Fe and Zn for growth were calculated and compared with measured values and we suggest that despite low Zn and Fe levels, these trace elements do not limit the growth of H. banksii.
Carfrae, JA, Sheppard, LJ, Raven, JA, Leith, ID, Stein, W, Crossley, A & Theobald, M 2004, 'Early effects of atmospheric ammonia deposition on Calluna vulgaris (L.) hull growing on an ombrotrophic peat bog', Water, Air, and Soil Pollution: Focus, vol. 4, no. 6, pp. 229-239.View/Download from: Publisher's site
This paper reports data from a field study investigating the impacts of elevated ammonia (NH3) deposition on Calluna vulgaris growing on an ombrotrophic peat bog in S.E. Scotland. Shoot extension, foliar N concentrations, chlorophyll concentration and chlorophyll fluorescence were measured during the second growing season of exposure to a gradient of ammonia concentrations. Results indicate that NH3 increases growth between 150-200 kg N ha-1y-1 cumulative deposition. Foliar N content increased significantly in response to NH3 cumulative deposition up to 400 kg N ha-1 y-1 whereas chlorophyll a content significantly decreased. Measurements of Fv/Fm suggest that although NH3 exposure altered the growth and reduced chlorophyll a, the efficiency of photosystem II was insensitive to NH3-N deposition at this stage. © Kluwer Academic Publishers 2004.
The cyanelles of glaucocystophyte ( = glaucophyte) algae and the thecate amoeba Paulinella were previously thought to be endosymbiotic cyanobacteria or intermediates in the evolution of plastids from endosymbiotic cyanobacteria. While the more recent determinations of the number and nature of genes in the cyanelle genome show that cyanelles are genetically plastids, they have retained cyanobacterial features which are never (peptidoglycan walls) or only very rarely (carboxysomes) found in other plastids. The hypothesis presented here relates the peptidoglycan wall and the function of carboxysomes to the involvement of active water effiux using contractile vacuoles or their functional equivalent in volume regulation of non-cyanelle compartments of the cell in at least some parts of the life cycle. The peptidoglycan wall could permit a relatively high intracyanelle osmolarity which is presumably needed for cyanelle growth. A high intracyanelle osmolarity permits the high inorganic carbon concentration in the cyanelle during photosynthesis which is required for a carboxysome-based inorganic carbon concentration mechanism. The occurrence of a contractile-vacuole-based mechanism of volume regulation in at least part of the life cycle argues on energetic grounds for a low osmolarity of the cytosol, with a consequent lack of potential for a high inorganic carbon concentration in the cell as a whole. These predictions are susceptible to experimental test.
Kustka, A, Sanudo-Wilhelmy, S, Carpenter, EJ, Capone, DG & Raven, JA 2003, 'A revised estimate of the iron use efficiency of nitrogen fixation, with special reference to the marine cyanobacterium Trichodesmium spp. (Cyanophyta)', JOURNAL OF PHYCOLOGY, vol. 39, no. 1, pp. 12-25.View/Download from: Publisher's site
Giordano, M, Norici, A, Forssen, M, Eriksson, M & Raven, JA 2003, 'An anaplerotic role for mitochondrial carbonic anhydrase in Chlamydomonas reinhardtii', PLANT PHYSIOLOGY, vol. 132, no. 4, pp. 2126-2134.View/Download from: Publisher's site
Raven, JA & Taylor, R 2003, 'Macroalgal growth in nutrient-enriched estuaries: A biogeochemical and evolutionary perspective', Water, Air, and Soil Pollution: Focus, vol. 3, no. 1, pp. 7-26.View/Download from: Publisher's site
Increased nutrient loading of a body of water leads to an increase in macroalgal growth. It is generally observed, however, that certain species thrive more than others, capitalising on the increased nutrient availability. These are usually small, fast-growing, ephemeral algae that often appear as nuisance blooms. This article discusses the correlation between nutrient increase and macroalgal bloom formation. From a historical perspective, the evolutionary history of nuisance macroalgae, and the habits available to them prior to anthropogenic influences on estuarine geochemistry are considered. The occurrence of macroalgal genera whose distribution is commonly related to estuaries with high nutrient loading is discussed, along with evidence suggesting that the ecophysiological traits of r-selected, ephemeral algae largely contribute to their ecological success and bloom-formation at nutrient-enriched sites. © 2003 Kluwer Academic Publishers.
Raven, JA, Johnston, AM, Kubler, JE, Korb, R, McInroy, SG, Handley, LL, Scrimgeour, CM, Walker, DI, Beardall, J, Clayton, MN, Vanderklift, M, Fredriksen, S & Dunton, KH 2002, 'Seaweeds in cold seas: Evolution and carbon acquisition', ANNALS OF BOTANY, vol. 90, no. 4, pp. 525-536.View/Download from: Publisher's site
Hill, PW, Raven, JA & Sutton, MA 2002, 'Leaf age-related differences in apoplastic NH4+ concentration, pH and the NH3 compensation point for a wild perennial', JOURNAL OF EXPERIMENTAL BOTANY, vol. 53, no. 367, pp. 277-286.View/Download from: Publisher's site
Longstaff, BJ, Kildea, T, Runcie, JW, Cheshire, A, Dennison, WC, Hurd, C, Kana, T, Raven, JA & Larkum, AWD 2002, 'An in situ study of photosynthetic oxygen exchange and electron transport rate in the marine macroalga Ulva lactuca (Chlorophyta)', PHOTOSYNTHESIS RESEARCH, vol. 74, no. 3, pp. 281-293.View/Download from: Publisher's site
Wolstencroft, RD & Raven, JA 2002, 'Photosynthesis: Likelihood of occurrence and possibility of detection on earth-like planets', Icarus, vol. 157, no. 2, pp. 535-548.View/Download from: Publisher's site
Although there are considerable technical challenges to be overcome during this decade, the prospects for the detection of Earth-like planets (ELPs) orbiting nearby stars are encouraging. If life has developed on some of the ELPs that may be discovered by sophisticated telescope systems, such as the Terrestrial Planet Finder, the detection of photosynthesis is an attractive possibility. Here we discuss the likely preconditions and subsequent events that have led to the occurrence of O2-producing photosynthesis on Earth and then extend this discussion to how this may have occurred on ELPs orbiting in the habitable zone of a variety of main-sequence stars from spectral type F0V to M0V. We point out how the need for liquid water and the need to avoid UV radiation have influenced the evolution of photosynthesis on Earth, how the absorption spectra of the dominant (chlorophyll) photosynthetic pigments may have been determined in natural selection, and how and when the evolution of the ability to use water as an electron donor took place. Models for the photosynthetic productivity of ELPs orbiting at the inner edge of the habitable zone are discussed both from aquatic and land-based photosynthesis, making some allowance for global cloud cover on the ELP. The photosynthetic generation of O2is greatest on cloud-free planets with hot (e.g., F0V) parent stars, though the advantage over cooler stars depends on the fraction of the planet covered by oceans. The low O2generation in ELPs orbiting cooler stars is due to the poor match between the parent star's spectral energy distribution and the assumption of terrestrial pigment properties. We discuss the possibility that a three- or four-photon mechanism might operate on such planets (as opposed to the two-photon system on Earth) and how it could influence the spectral properties of the ELP. We also emphasize the role of tectonic and other geological processes as well as biology in determining the O2level on Earth and on ELPs....
Riisgard, HU, Quinn, G, Fee, E, Larsen, PS, Shumway, SE, Gili, JM, Kiorboe, T, Hagerman, L, Beninger, P, Tessier, A, Raven, J, Middelburg, JJ, Lesser, M, Gremare, A, Cole, J, Larsen, ON, Beukema, JJ, Reise, K, Canfield, D & Kinne, O 2001, 'The peer-review system: time for re-assessment?', AQUATIC MICROBIAL ECOLOGY, vol. 26, no. 1, pp. 305A-313A.
Raven, JA 2001, 'An aquatic perspective on the concepts of Ingestad relating plant nutrition to plant growth.', Physiologia plantarum, vol. 113, no. 3, pp. 301-307.View/Download from: Publisher's site
The Ingestad approach to the culture of higher terrestrial plants for physiological studies is discussed in relation to a number of resources, organisms and growth situations that were not part of the original design and rationale of Ingestad's methodology. The additional resource considered is photosynthetically active radiation, and difficulties of applying the Ingestad approach to this resource as well as to atmospheric CO2 are considered. The relationship of the Ingestad approach to reductionist studies based on enzyme kinetic studies is then briefly considered. The organisms considered next are aquatic plants, including both micro- and macrophytes. The consideration of photosynthetic microorganisms leads to a comparison of the Ingestad approach with growth in batch, and in continuous (chemostat and turbidostat) cultures, and with studies on growth in synchronous cultures in which cyclic changes in cell composition in the cell growth and division cycle can be identified. The natural environmental conditions for these organisms are a natural extension of the light/dark synchronization of laboratory cultures, and the bloom (batch culture equivalent to new production) and of grazing and parasitism removing biomass and recycling nutrients (chemostat or turbidostat culture equivalent to recycled production) situations for phytoplankton. The overall conclusion is that, while the Ingestad approach is a useful mirror in which to examine other concepts of plant resource acquisition and manipulation, the Ingestad methodology seems to make assumptions about the intrinsic growth rate and composition of plants that cannot be independently verified.
Raven, JA & Weyers, JDB 2001, 'Significance of epidermal fusion and intercalary growth for angiosperm evolution', TRENDS IN PLANT SCIENCE, vol. 6, no. 3, pp. 111-113.View/Download from: Publisher's site
Hill, PW, Raven, JA, Loubet, B, Fowler, D & Sutton, MA 2001, 'Comparison of gas exchange and bioassay determinations of the ammonia compensation point in Luzula sylvatica (Huds.) Gaud.', PLANT PHYSIOLOGY, vol. 125, no. 1, pp. 476-487.View/Download from: Publisher's site
Sanudo-Wilhelmy, SA, Kustka, AB, Gobler, CJ, Hutchins, DA, Yang, M, Lwiza, K, Burns, J, Capone, DG, Raven, JA & Carpenter, EJ 2001, 'Phosphorus limitation of nitrogen fixation by Trichodesmium in the central Atlantic Ocean', NATURE, vol. 411, no. 6833, pp. 66-69.View/Download from: Publisher's site
Bausenwein, U, Millard, P, Thornton, B & Raven, JA 2001, 'Seasonal nitrogen storage and remobilization in the forb Rumex acetosa', FUNCTIONAL ECOLOGY, vol. 15, no. 3, pp. 370-377.View/Download from: Publisher's site
Geider, RJ, Delucia, EH, Falkowski, PG, Finzi, AC, Grime, JP, Grace, J, Kana, TM, La Roche, J, Long, SP, Osborne, BA, Platt, T, Prentice, IC, Raven, JA, Schlesinger, WH, Smetacek, V, Stuart, V, Sathyendranath, S, Thomas, RB, Vogelmann, TC, Williams, P & Woodward, FI 2001, 'Primary productivity of planet earth: biological determinants and physical constraints in terrestrial and aquatic habitats', GLOBAL CHANGE BIOLOGY, vol. 7, no. 8, pp. 849-882.View/Download from: Publisher's site
Raven, JA & Edwards, D 2001, 'Roots: Evolutionary origins and biogeochemical significance', Journal of Experimental Botany, vol. 52, no. SPEC. ISS. MAR., pp. 381-401.
Roots, as organs distinguishable developmentally and anatomically from shoots (other than by occurrence of stomata and sporangia on above-ground organs), evolved in the sporophytes of at least two distinct lineages of early vascular plants during their initial major radiation on land in Early Devonian times (c. 410-395 million years ago). This was some 15 million years after the appearance of tracheophytes and c. 50 million years after the earliest embryophytes of presumed bryophyte affinity. Both groups are known initially only from spores, but from comparative anatomy of extant bryophytes and later Lower Devonian fossils it is assumed that, during these times, below-ground structures (if any) other than true roots fulfilled the functions of anchorage and of water and nutrient acquisition, despite lacking an endodermis (as do the roots of extant Lycopodium spp.). By 375 million years ago root-like structures penetrated almost a metre into the substratum, greatly increasing the volume of mineral matter subject to weathering by the higher than atmospheric CO2levels generated by plant and microbial respiration in material with restricted diffusive contact with the atmosphere. Chemical weathering consumes CO2in converting silicates into bicarbonate and Si(OH)4. The CO2consumed in weathering ultimately came from atmospheric CO2via photosynthesis and respiration; this use of CO2probably accounts for most of the postulated 10-fold decrease in atmospheric CO2from 400-350 million years ago, with significant effects on shoot evolution. Subsequent evolution of roots has yielded much-branched axes down to 40 m diameter, a lower limit set by long-distance transport constraints. Finer structures involved in the uptake of nutrients of low diffusivity in soil evolved at least 400 million years ago as arbuscular mycorrhizas or as evaginations of 'roots' ('root hairs').
Raven, JA, Walker, DI, Jensen, KR, Handley, LL, Scrimgeour, CM & McInroy, SG 2001, 'What fraction of the organic carbon in sacoglossans is obtained from photosynthesis by kleptoplastids? An investigation using the natural abundance of stable carbon isotopes', MARINE BIOLOGY, vol. 138, no. 3, pp. 537-545.View/Download from: Publisher's site
Raven, JA, Beardall, J, Chudek, JA, Scrimgeour, CM, Clayton, MN & McInroy, SG 2001, 'Altritol synthesis by Notheia anomala', PHYTOCHEMISTRY, vol. 58, no. 3, pp. 389-394.View/Download from: Publisher's site
Bausenwein, U, Millard, P & Raven, JA 2001, 'Remobilized old-leaf nitrogen predominates for spring growth in two temperate grasses', NEW PHYTOLOGIST, vol. 152, no. 2, pp. 283-290.View/Download from: Publisher's site
Taylor, R, Fletcher, RL & Raven, JA 2001, 'Preliminary studies on the growth of selected 'Green tide' algae in laboratory culture: Effects of irradiance, temperature, salinity and nutrients on growth rate', BOTANICA MARINA, vol. 44, no. 4, pp. 327-336.View/Download from: Publisher's site
Raven, JA 2001, 'A role for mitochondrial carbonic anhydrase in limiting CO2 leakage from low CO2-grown cells of Chlamydomonas reinhardtii', Plant, Cell and Environment, vol. 24, no. 2, pp. 261-265.View/Download from: Publisher's site
A model is presented which quantifies a possible role for the carbonic anhydrase in the mitochondrial matrix of Chlamydomonas reinhardtii which incorporates the observation that the expression of this enzyme is increased under growth conditions in which the expression of the carbon dioxide-concentrating mechanism is increased. It is assumed that the inorganic carbon enters the cytosol from the medium, and leaves the cytosol to the plastids, as HCO3- and that there is negligible carbonic anhydrase activity in the cytosol. The role of the mitochondrial carbonic anhydrase is suggested to be the conversion to HCO3- of the CO2 produced in the mitochondria in the light from tricarboxylic acid cycle activity and from decarboxylation of glycine in any photorespiratory carbon oxidation cycle activity which is not suppressed by the carbon concentrating mechanism. If there is a HCO3- channel in the inner mitochondrial membrane then almost all of the inorganic carbon leaves the mitochondria as HCO3-, thus limiting the potential for CO2 leakage through the plasmalemma. This mechanism could increase inorganic C supply to ribulose bisphosphate carboxylase-oxygenase by some 10% at the energetic expense of less than 1% of the total ATP generation by plastids plus mitochondria.
The predominant silicon (Si) compound in the soil solution is silicic acid, and the baseline condition for Si transport into and within a plant with no membrane channels or transporters which can move Si compounds is the movement of silicic acid across membranes by dissolving in the lipid phase of the membrane ('lipid solution' transport). Based on the best current estimates of 'lipid solution' permeability of membranes to silicic acid (10-10 m s-1), even the lowest Si contents in plants cannot be explained in terms of the soil solution silicic acid concentration and the lipid solution mechanism, and a component of silicic acid entry coupled to transpiratory water uptake is required. For Oryza (rice) and, under some conditions, Hordeum (barley), and Phaseolus (bean), active influx of silicic acid is needed to account for the observed silica content. Further work is needed as to the mechanism of active tranport of silicic acid following the lead of the characterization of Na+-coupled transport in a diatom, and on how silicic acid is coupled to water transport (involving aquaporins?), and on the phloem mobility of silicic acid. © 2001 Elsevier B.V. All rights reserved.
Ivanov, AG, Park, YI, Miskiewicz, E, Raven, JA, Huner, NPA & Oquist, G 2000, 'Iron stress restricts photosynthetic intersystem electron transport in Synechococcus sp, PCC 7942', FEBS LETTERS, vol. 485, no. 2-3, pp. 173-177.View/Download from: Publisher's site
McKenzie, JD, Black, KD, Kelly, MS, Newton, LC, Handley, LL, Scrimgeour, CM, Raven, JA & Henderson, RJ 2000, 'Comparisons of fatty acid and stable isotope ratios in symbiotic and non-symbiotic brittlestars from Oban Bay, Scotland', Journal of the Marine Biological Association of the United Kingdom, vol. 80, no. 2, pp. 311-320.View/Download from: Publisher's site
The bed-forming brittlestars Ophiothrix fragilis, Ophiocomina nigra and Amphiura chiajei from Oban Bay, Scotland were studied using methods previously employed to study chemoautotrophic symbioses. Ophiothrix fragilis and A. chiajei both contain symbiotic bacteria (SCB) while Ophiocomina nigra is non-symbiotic. Samples were taken of Ophiothrix fragilis at approximately two-week intervals for one year. Symbiotic bacteria numbers were determined by direct counting of homogenates of the arms of 50 individual brittlestars. Water samples were analysed for chlorophyll content. Stable isotope ratios for carbon and nitrogen were determined for each homogenate sample. Regular SCB counts were made on the infaunal brittlestar A. chiajei. Homogenate samples of Ophiothrix fragilis, A. chiajei and the non-symbiotic Ophiocomina nigra were analysed to produce fatty acid profiles for each species. Symbiotic bacteria count varied by up to one order of magnitude in both Ophiothrix fragilis and A. chiajei with no evidence of seasonality in this variation. Symbiotic bacteria number was inversely correlated with 15N but no relationship was established with 13C. 16:17 and 18:1.7 fatty acids were used as putative bacterial markers. Both symbiotic species had higher percentages of 16:17 than the non-symbiotic Ophiocomina nigra. However, only Ophiothrix fragilis appeared to receive appreciable quantities of 18:17 from its SCB. The SCB are heterotrophic and may contribute to the nitrogen budget of the host. The two symbiotic species studied here derive the bulk of their nutrition from conventional feeding but SCB make significant, additional contributions.
Van Vuuren, MMI, Robinson, D, Scrimgeour, CM, Raven, JA & Fitter, AH 2000, 'Decomposition of 13C-labelled wheat root systems following growth at different CO2 concentrations', Soil Biology and Biochemistry, vol. 32, no. 3, pp. 403-413.View/Download from: Publisher's site
We tested whether the amounts of carbon (C) mineralized from decomposing wheat (Triticum aestivum L. cv. Tonic) roots were related to the quantity (i.e. root dry weight per plant) or the chemical composition of material which had been grown at ambient or elevated CO2 concentrations (350 or 700 mol CO2 mol-1). Plants were grown in 13C-depleted CO2 to distinguish root-derived C from soil-derived C. Over periods of up to ca. 400 d, root C, soil C and nitrogen (N) mineralization were measured from: (i) root systems left in situ in soil; (ii) soil after removal of visible roots; and (iii) equal amounts of roots added to fresh soil. Root systems in situ showed transiently faster C mineralization rates after growth at elevated [CO2] compared with ambient [CO2]. Ultimately, there were no [CO2]-related differences in the amounts of C or N mineralized from root systems in situ. Specific rates of C loss from extracted roots were not significantly different for roots from the two [CO2] treatments. The potential accuracy of the 13C method was demonstrated and 13C/12C fractionation during root decomposition was negligible. We conclude that when wheat is grown under elevated [CO2], subsequent root decomposition will not necessarily be affected. If it does, it is likely to do so via an effect of [CO2] on the amounts of root material produced per unit of soil rather than on the chemical quality of that material. (C) 2000 Elsevier Science Ltd.
Poole, I, Lawson, T, Weyers, JDB & Raven, JA 2000, 'Effect of elevated CO2 on the stomatal distribution and leaf physiology of Alnus glutinosa', NEW PHYTOLOGIST, vol. 145, no. 3, pp. 511-521.View/Download from: Publisher's site
Raven, JA, Kubler, JE & Beardall, J 2000, 'Put out the light, and then put out the light', JOURNAL OF THE MARINE BIOLOGICAL ASSOCIATION OF THE UNITED KINGDOM, vol. 80, no. 1, pp. 1-25.View/Download from: Publisher's site
Logan, KAB, Thomas, RJ & Raven, JA 2000, 'Effect of ammonium and phosphorus supply on H+production in gel by two tropical forage grasses', Journal of Plant Nutrition, vol. 23, no. 1, pp. 41-54.View/Download from: Publisher's site
The effect of the supply of ammonium (NH4+) and phosphorus (P) in gel on the amounts of hydrogen ion (H+) excreted from plant roots was studied with Brachiaria humidicola (a highly acid-soil tolerant tropical grass) and B. brizantha (less acid-soil tolerant) grown in soil in a glasshouse. The H+production was measured over 24 h in agar gel containing full nutrient solution with a range of NH4+-N levels (0, 0.25, 0.5, and 5.0 mM NH4+-N). Highly soluble P, K2HPO4, or relatively insoluble P, rock P, was supplied at four concentrations (0, 11.5, 34.5, or 115 M P) in the gel. Increasing NH4+concentration in the gel increased H+production for both grasses, but there was some inhibition of growth for B. brizantha at the highest N concentration. For B. humidicola, but not B. brizantha H+production was greater with 34.5 M K2HPO4than 11.5 M K2HPO4. At 34.5 M P for both grasses there was no difference in H+production when P was supplied as rock P or K2HPO4. With 11.5 M P both grasses produced less acid in the gel with the rock P compared with K2HPO4. The reduced H+production is probably due to a lower availability of P in the rock P compared with K2HPO4. This effect was greater with B. brizantha than B. humidicola, implying that 11.5 M rock P was not able to supply sufficient P for the growth of B. brizantha. Brachiaria humidicola was able to dissolve more rock P than B. brizantha or alternatively, the growth of B. humidicola was less adversely affected by the low P supply from rock P than B. brizantha. Plant-induced acidity does not seem to occur as a response to a lack of available P, but rather these grasses only produce acid if there are enough nutrients for growth, i.e., both NH4+and P. If either N or P is limiting, growth is limited as is NH4+uptake, so that H+production is curtailed.
Raven, JA, Evans, MCW & Korb, RE 1999, 'The role of trace metals in photosynthetic electron transport in O-2-evolving organisms', PHOTOSYNTHESIS RESEARCH, vol. 60, no. 2-3, pp. 111-149.View/Download from: Publisher's site
Raven, JA 1999, 'Cell geometry revisited: Realistic shapes and accurate determination of cell volume and surface area from microscopic measurements', Journal of Phycology, vol. 35, no. 2, pp. 209-210.
Handley, LL, Austin, AT, Robinson, D, Scrimgeour, CM, Raven, JA, Heaton, THE, Schmidt, S & Stewart, GR 1999, 'The 15 N natural abundance ( 15 N) of ecosystem samples reflects measures of water availability', Australian Journal of Plant Physiology, vol. 26, no. 2, pp. 185-199.View/Download from: Publisher's site
We assembled a globally-derived data set for site-averaged foliar 15 N, the 15 N of whole surface mineral soil and corresponding site factors (mean annual rainfall and temperature, latitude, altitude and soil pH). The 15 N of whole soil was related to all of the site variables (including foliar 15 N) except altitude and, when regressed on latitude and rainfall, provided the best model of these data, accounting for 49% of the variation in whole soil 15 N. As single linear regressions, site-averaged foliar 15 N was more strongly related to rainfall than was whole soil 15 N. A smaller data set showed similar, negative correlations between whole soil 15 N, site-averaged foliar d15N and soil moisture variations during a single growing season. The negative correlation between water availability (measured here by rainfall and temperature) and soil or plant 15 N fails at the landscape scale, where wet spots are 15 N-enriched relative to their drier surroundings. Here we present global and seasonal data, postulate a proximate mechanism for the overall relationship between water availability and ecosystem 15 N and, newly, a mechanism accounting for the highly 15 N-depleted values found in the foliage and soils of many wet/cold ecosystems. These hypotheses are complemented by documentation of the present gaps in knowledge, suggesting lines of research which will provide new insights into terrestrial N-cycling. Our conclusions are consistent with those of Austin and Vitousek (1998) that foliar (and soil) 15 N appear to be related to the residence time of whole ecosystem N. © CSIRO 1999.
Logan, KAB, Thomas, RJ & Raven, JA 1999, 'Hydrogen ion production and ammonium uptake by two tropical forage grasses', Journal of Plant Nutrition, vol. 22, no. 1, pp. 53-66.View/Download from: Publisher's site
The amounts of hydrogen ion (H+) excreted from roots and the relationship of acid production with the uptake of ammonium (NH4/+) were studied with Brachiaria dictyoneura (a highly acid-soil tolerant tropical grass) and B. brizantha (less acid-soil tolerant) grown in soil in a glasshouse. At six dates between 39 and 73 d the H+ production in agar gel and NH4/+ uptake from solution were measured over 24 h for ten replicate plants of each species. The agar gel and solution contained the same nutrients with 5 mM N supplied as NH4/+-N. Brachiaria dictyoneura tended to have greater total dry matter (DM) production than B. brizantha mainly as a result of greater root than shoot DM production. Daily H+ production increased with increasing DM and was always greater for B. dictyoneura than B. brizantha. Similarly NH4/+ uptake was always greater for B. dictyoneura than B. brizantha and was linearly related (R2=0.85) to H± production in gel. Hydrogen ion production/ NH4± uptake ratios were 0.3 to 0.5 for B. dictyoneura and 0.1 to 0.3 for B. brizantha. Hence as well as taking up more NH4/+ B. dictyoneura also produced more H± for every mole of NH4/+ taken up than B. brizantha. Differences in the pH changes between the gels and solutions and the effects of the inclusion of NO3 in the media are discussed. It is concluded that for pastures B. brizantha would be a better choice than B. dictyoneura in that it would have less of an acidifying effect on the soil without detracting from the herbage yield.
Raven, JA 1999, 'Constraints on marine algal invasion of low-salinity environments: Sex in the Baltic', JOURNAL OF PHYCOLOGY, vol. 35, no. 2, pp. 210-212.
Raven, JA 1999, 'Photosynthesis in the intertidal zone: Algae get an airing', JOURNAL OF PHYCOLOGY, vol. 35, no. 6, pp. 1102-1105.
Andrews, M, Sprent, JI, Raven, JA & Eady, PE 1999, 'Relationships between shoot to root ratio, growth and leaf soluble protein concentration of Pisum sativum, Phaseolus vulgaris and Triticum aestivum under different nutrient deficiencies', PLANT CELL AND ENVIRONMENT, vol. 22, no. 8, pp. 949-958.
The earliest O2-evolvers were marine cyanobacteria (3.5 billion years ago) with marine eukaryotic phototrophs from 2.0 billion years ago. These organisms were, and are, poikilohydric, i.e., cannot remain hydrated when exposed to a desiccating atmosphere (as can occur for intertidal benthic algae and cyanobacteria at low tide). The smallest marine primarily poikilohydric O2-evolvers are close to the lower size limit imposed by non-scaleable components such as minimum genome size and constant membrane thickness, with cyanobacterial unicells 0.65 m in diameter and eukaryotic unicells 0.95 m in diameter. The largest (multicellular) marine primarily aquatic poikilohydric O2-evolvers are brown algae at least 60 m long and over 100 kg fresh mass; there are no obvious constraints on the maximum size of such organisms. In freshwaters the size range for primarily poikilohydric O2-evolving organisms is smaller, due to the absence of very large organisms. An even smaller size range characterizes terrestrial algae and cyanobacteria which have occurred for about 1 billion years. Desiccation-tolerant cyanobacterium and algae (intertidal, freshwater, terrestrial) are at the lower end of the size ranges. Embryophytic terrestrial O2-evolvers arose some 450 million years ago and were than all poikilohydric and (probably) desiccation-tolerant. Embryophytic defining structural features require organisms of at least 100 m equivalent spherical diameter for both gametophyte and sporophyte phases. Primarily poikilohydric embryophytes are not more than 1 m tall as a result of a mechanistically mysterious size limit for desiccation-tolerant organisms. Homoiohydric embryophytes evolved some 420 million years ago in the sporophyte phase (later to become the dominant terrestrial vegetation) and possibly in the gametophyte phase (although no such homoiohydric gametophytes are known today). The homoiohydric features of gas spaces, stomata, cuticle, endohydric water conducting system and wate...
Newman, JR & Raven, JA 1999, 'CO2 is the main inorganic C species entering photosynthetically active leaf protoplasts of the freshwater macrophyte Ranunculus penicillatus ssp. pseudofluitans', Plant, Cell and Environment, vol. 22, no. 8, pp. 1019-1026.View/Download from: Publisher's site
Submerged aquatic macrophytes growing in water where free CO2 is unavailable (above pH 8.2) must use mechanisms to supply external dissolved inorganic carbon in a form available to chloroplasts (CO2). Active transport of HCO3- across the plasmalemma has not been proven to be widespread in aquatic macrophytes and catalytic conversion of HCO3- to CO2 is the usual supply mechanism in submerged macrophytes. The interaction of leaf form and function in this respect was investigated in the linear, submerged leaves of Ranunculus penicillatus (Dumort.) Bab ssp. pseudofluitans (Syme) S.Webster. Viable protoplasts were isolated using a mixture of cell wall degrading enzymes optimized for this species. Protoplast viabilities greater than 80% after 5 h of isolation were achieved. Photosynthetic rates of isolated protoplasts were comparable with that of intact plant tissue. Results of carbon isotopic disequilibrium experiments showed that CO2 was the preferred species of dissolved inorganic carbon for photosynthesis by protoplasts and that HCO3- which predominates in the plant's natural environment mainly contributes by supplying CO2 outside the cells.
Kubler, JE, Johnston, AM & Raven, JA 1999, 'The effects of reduced and elevated CO2 and O-2 on the seaweed Lomentaria articulata', PLANT CELL AND ENVIRONMENT, vol. 22, no. 10, pp. 1303-1310.View/Download from: Publisher's site
Academic Press, 1997. $84.00 hbk (xi+303 pages) ISBN 0 12 083490 1.
Korb, RE, Raven, JA & Johnston, AM 1998, 'Relationship between aqueous CO2 concentrations and stable carbon isotope discrimination in the diatoms Chaetoceros calcitrans and Ditylum brightwellii', MARINE ECOLOGY PROGRESS SERIES, vol. 171, pp. 303-305.View/Download from: Publisher's site
Raven, JA & Yin, ZH 1998, 'The past, present and future of nitrogenous compounds in the atmosphere, and their interactions with plants', NEW PHYTOLOGIST, vol. 139, no. 1, pp. 205-219.View/Download from: Publisher's site
Raven, JA 1998, 'Extrapolating feedback processes from the present to the past', Philosophical Transactions of the Royal Society B: Biological Sciences, vol. 353, no. 1365, pp. 19-28.View/Download from: Publisher's site
Extant terrestrial vegetation alters its physical environment via its albedo, and its influence on immediate temperature via stomatal and boundary-layer influences of energy dissipation as sensible and latent heat; aquatic vegetation also controls albedo (e.g. coccolithophorids) and, by competing with water for electromagnetic energy absorption, the depth of the mixed layer and hence the quantity of nutrients trapped for the spring bloom. Both aquatic and terrestrial vegetation have had, together with microbial and geological processes, an influence on O2and CO2levels, and hence on the availability and biological functioning of Fe, Mn, Cu, Zn, Se and P, and the relative competitive advantage of C3versus C4, crassulacean acid metabolism (CAM) and carbon concentration mechanism (CCM) organisms. Less directly, changes in primary productivity impact on the production of CH4and N2O which, like CO2, are greenhouse gases, while some (marine) primary producers yield dimethyl sulphide (and hence cloud condensation nuclei, with effects on cloudiness) and halocarbons (via, in part, O2-dependent processes), partly negating the O3attenuation of UV-B radiation. These effects can be related to the terrestrial embryophytic vegetation back to ca. 450Ma, and to eukaryotic marine vegetation back to at least 1.7, and probably 2.1Ga, with implications for inter alia C3versus C4, CAM and CCM photosynthesis, and Fe acquisition mechanisms. Even earlier (3.8 Ga onwards), prokaryotes may have influenced CO2levels and hence controlled (as they did later) surface temperature. By producing O2, they may have led to decreasing availability of Fe, Mn and P (and utility of Se?), and increasing availability of Cu (and Zn?) that shaped the biochemistry on which later biogeochemistry was based.
Yin, ZH & Raven, JA 1998, 'Influences of different nitrogen sources on nitrogen- and water-use efficiency, and carbon isotope discrimination, in C-3 Triticum aestivum L. and C-4 Zea mays L. plants', PLANTA, vol. 205, no. 4, pp. 574-580.View/Download from: Publisher's site
Brenchley, JL, Raven, JA & Johnston, AM 1998, 'Carbon and nitrogen allocation patterns in two intertidal fucoids: Fucus serratus and Himanthalia elongata (Phaeophyta)', EUROPEAN JOURNAL OF PHYCOLOGY, vol. 33, no. 4, pp. 307-313.View/Download from: Publisher's site
Beardall, J, Beer, S & Raven, JA 1998, 'Biodiversity of marine plants in an era of climate change: Some predictions based on physiological performance', BOTANICA MARINA, vol. 41, no. 1, pp. 113-123.View/Download from: Publisher's site
Skene, KR, Sutherland, JM, Raven, JA & Sprent, JI 1998, 'Cluster root development in Grevillea robusta (Proteaceae): II. The development of the endodermis in a determinate root and in an indeterminate, lateral root', New Phytologist, vol. 138, no. 4, pp. 733-742.View/Download from: Publisher's site
Light, fluorescence and electron microscopy were employed to follow the development of the endodermis in cluster roots and lateral roots of Grevillea robusta A. Cunn. ex R. Br. Endodermal cells had three different origins: rootlet endodermis arose from the rootlet meristem; endodermis covering the primordium shortly after initiation came from division of parental endodermis; cells at the junction between parent and rootlet endodermis developed from re-differentiated rootlet cortical cells. In the cluster root, the Casparian band formed in three ways, and was not initially present opposite the two sets of single xylem elements in the rootlet stele. A new clearing technique was developed that allowed visualization of xylem, suberized endodermis, Casparian band formation and phenolic compounds. In lateral roots, endodermal differentiation was asynchronous, but was related to position relative to protoxylem poles. However, the observed delay began before these poles had differentiated. At the tip of mature rootlets, which are determinate, the endodermis terminates in a 'dome' of cells, with the initial cell differentiating as an endodermal cell. Results are discussed in terms of determinate development in roots and the spatial and temporal contexts within which this development takes place.
Skene, KR, Raven, JA & Sprent, JI 1998, 'Cluster root development in Grevillea robusta (Proteaceae) - I. Xylem, pericycle, cortex, and epidermis development in a determinate root', NEW PHYTOLOGIST, vol. 138, no. 4, pp. 725-732.View/Download from: Publisher's site
Raven, JA 1998, 'Insect and angiosperm diversity in marine environments: further comments on van der Hage', FUNCTIONAL ECOLOGY, vol. 12, no. 6, pp. 977-979.
Raven, JA 1998, 'The past, present and future of nitrogenous compounds in the atmosphere, and their interactions with plants', New Phytologist, vol. 139, no. 1, pp. 201-204.
Raven, J 1997, 'Green policy', NEW SCIENTIST, vol. 156, no. 2105, pp. U6-U6.
Poole, LJ, Scrimgeour, C, Korb, RB, McInroy, S & Raven, JA 1997, 'The use of 1802 uptake and 1602 production by Enteromorpha intestinalis to quantify 02 uptake processes in algae', PHYCOLOGIA, vol. 36, no. 4, pp. 89-89.
Raven, JA 1997, 'The role of marine biota in the evolution of terrestrial biota: Gases and genes. Atmospheric composition and evolution of terrestrial biota', Biogeochemistry, vol. 39, no. 2, pp. 139-164.View/Download from: Publisher's site
There is greater biodiversity (in the sense of genetic distance among higher taxa) of extant marine than of terrestrial O2-evolvers. In addition to contributing the genes from one group of algae (Class Charophyceae, Division Chlorophyta) to produce by evolution the dominant terrestrial plants (Embryophyta), the early marine O2-evolvers greatly modified the atmosphere and hence the land surface when the early terrestrial O2-evolvers grew. The earliest terrestrial phototrophs (from geochemical evidence) occurred 1.2 Ga ago, over 0.7 Ga before the Embryophyta evolved, but well after the earliest marine (cyanobacterial) O2 evolvers (3.45 Ga) and marine eukaryotic O2 evolvers (2.1 Ga). Even by the time of evolution of the earliest terrestrial O2-evolvers the marine O2-evolvers had modified the atmosphere and land environment in at least the following five ways. Once photosynthetic O2 paralleling organic C burial had satisfied marine (Fe2+, S2-) reductants, atmospheric O2 built (1) up to a considerable fraction of the extant value (although some was consumed in oxidising terrestrial exposed Fe2+) and (2) provided stratospheric O3 and thus a UV-screen. (3) CO2 drawdown to ~20-30 times the extant level is attributable to net production, and burial, of organic C in the oceans (plus other geological processes). Furthermore, (4) their production of volatile organic S compounds could have helped to supply S to inland sites but also (5) delivered Cl and Br to the stratosphere thus lowering the O3 level and the extent of UV screening.
VanVuuren, MMI, Robinson, D, Fitter, AH, Chasalow, SD, Williamson, L & Raven, JA 1997, 'Effects of elevated atmospheric CO2 and soil water availability on root biomass, root length, and N, P and K uptake by wheat', NEW PHYTOLOGIST, vol. 135, no. 3, pp. 455-465.View/Download from: Publisher's site
Yin, ZH & Raven, JA 1997, 'A comparison of the impacts of various nitrogen sources on acid-base balance in C3Triticum aestivum L. and C4Zea mays L. plants', Journal of Experimental Botany, vol. 48, no. 307, pp. 315-324.
This work aimed to study the impacts of acquisition and assimilation of various nitrogen sources, i.e. NO3, NH4/+or NH4NO3, in combination with gaseous NH3on plant growth and acid-base balance in higher plants. Plants of C3Triticum aestivum L. and C4Zea mays L. grown with shoots in ambient air in hydroponic culture solutions with 2 mol m-3of nitrogen source as NO3/-, NH4/+or NH4NO3for 21 d and 18 d, respectively, had their shoots exposed either to 320 g m-3NH3or to ambient air for 7 d. Variations in plant growth (leaves, stubble and roots), and OH-and H+extrusions as well as the relative increases in nitrogen, carbon and carboxylate were determined. These data were computed as H+/N, DH+/C, (C-A)/N, and (C-A)/C to analyse influences of different nitrogen sources on acid-base balance in C3Triticum aestivum and C4Zea mays plants. Root growth in dry weight gain was significantly reduced by treatment with 320 g m-3NH3in Triticum aestivum and Zea mays growing with different N-forms, whereas leaf growth was not significantly affected by NH3. In comparison with C3Triticum aestivum, non-fumigated C4Zea mays had low ratios of OH-/N in NO3/--grown plants and of H+/N in NH4/+-and NH4NO3-grown plants. Utilization of NH3from the atmosphere reduced both the OH-/N ratios in NO3/--grown plants and the H+/N ratio in NH4/+- and NH4NO3-grown plants of both species. Furthermore, Zea mays had higher ratios of (C-A)/N in NH4/+-and NH4NO3-grown plants than Triticum aestivum. This means that C4Zea mays had synthesized more organic anion per unit increase in organic N than C3Triticum aestivum plants. Within both species, different nitrogen sources altered the ratios of (C-A)/N in the order: NH4NO3>NH4/+>NO3/-. Fumigation with NH3increased organic acid synthesis in NO3/--and NH4/+grown plants of Triticum aestivum, whereas it decreased organic acid synthesis in Zea mays plants under the same conditions. Furthermore, these differences in acid-base regulation between C3Tr...
Raven, JA & Scrimgeour, CM 1997, 'The influence of anoxia on plants of saline habitats with special reference to the sulphur cycle', ANNALS OF BOTANY, vol. 79, pp. 79-86.
Korb, RE, Saville, PJ, Johnston, AM & Raven, JA 1997, 'Sources of inorganic carbon for photosynthesis by three species of marine diatom', Journal of Phycology, vol. 33, no. 3, pp. 433-440.View/Download from: Publisher's site
The utilization of inorganic carbon by three species of marine diatom, Skeletonema costatum (Grev.) Cleve. Ditylum brightwellii (West) Grun., and Chaetoceros calcitrans Paulsen was investigated using an inorganic carbon isotopic disequilibrium technique and inorganic carbon dose-response curves. Stable carbon isotope data of the diatoms are also presented. Observed rates of photosynthetic oxygen evolution were greater than could be accounted for by the theoretical rate of CO2 supply from the uncatalyzed dehydration of HCO3/- in the external medium, suggesting use of HCO3/- as an inorganic carbon source. Data from the isotopic disequilibrium experiment demonstrate the use of both HCO3/- and CO2 for photosynthesis. Carbon isotope discrimination values support the use of HCO3/- by the diatoms.
Plasmodesmata in photosynthetic eukaryotes are found in all embryophytes, in many members of the Chlorophyta, and in the Phaeophyceae. The Phaeophyceae and the Chlorophyta clearly developed cell walls and multicellularity independently, so that (in the absence of lateral gene transfer) plasmodesmata evolved independently in these groups. The minimum number of independent origins of plasmodesmata in the Chlorophyta based on molecular phylogenies is two (Chlorophyceae sensu lato, Charophyceae sensu lato). Other intercellular connections in members of the Chlorophyta (Ctenocladus, Smithsoniella, Volvox) are structurally very different from true plasmodesmata. Recently published taxonomies of the Chlorophyta have five classes (Chlorophyceae, Oedegoniophyceae, Trentepohliophyceae, Klebsormidiophyceae and Charophyceae sensu stricto) with plasmodesmata out of a total of thirteen. However, it is by no means clear that these classes all acquired plasmodesmata independently.
Yoneyama, T, Handley, LL, Scrimgeour, CM, Fisher, DB & Raven, JA 1997, 'Variations of the natural abundances of nitrogen and carbon isotopes in Triticum aestivum, with special reference to phloem and xylem exudates', New Phytologist, vol. 137, no. 2, pp. 205-213.View/Download from: Publisher's site
This work explored whether the natural abundances of carbon and nitrogen isotopes could be used to describe the movement of C and N within wheat plants; we also considered whether isotopic analyses of aphids or their honeydew would substitute for direct analysis of phloem exudate. The 13C of ears and roots (sinks) most closely matched those of the sugars + organic acids fraction (sources) in both growth stages; phloem 13C matched that of leaf blade sugars. Xylem exudate 13C matched no other putative (and measured) source in the ear-forming stage and matched that of whole roots and ears in the grain-filling stage. The 15N of grain and roots (sinks) resembled that of leaf amino acids (sources) in the ear-forming stage. In the grain-filling stage, ear 15N continued to resemble that of leaf amino acids, and 15N of roots most closely resembled that of whole leaves. In the grain-filling stage, phloem 15N fell between that of leaf blade amino acids and that of whole leaves and was 15N-depleted relative to internal and external NO3-N. In both growth stages, xylem exudate 15N was less than that of soil NO3--N and and more than that of residual soil N after mineral N extraction. The isotopic values are generally in agreement with data from other approaches, such as isotope labelling; they show NO3--N reduction in both shoots and roots of wheat and significant N recycling (root-shoot-phloem-root) and C movement. Aphids might serve as a substitute for isotopic analysis of phloem 15N, having the same value as their food source. Their excreta was 15N-enriched relative to phloem.
Raven, JA 1997, 'Inorganic carbon acquisition by marine autotrophs', ADVANCES IN BOTANICAL RESEARCH, VOL 27, vol. 27, pp. 85-209.
Brenchley, JL, Raven, JA & Johnston, AM 1997, 'Resource acquisition in two intertidal fucoid seaweeds, Fucus serratus and Himanthalia elongata: Seasonal variation and effects of reproductive development', Marine Biology, vol. 129, no. 2, pp. 367-375.View/Download from: Publisher's site
Seasonal variations and the effect of reproductive development on resource acquisition by two intertidal fucoid species, the iteroparous Fucus serratus L. and the semelparous Himanthalia elongata (L.) S. F. Gray were examined. The oxygen-exchange characteristics of vegetative apical tissue of both non-fertile and fertile plants and receptacle tissue were compared at monthly intervals throughout reproductive development. Respiratory rates in non-fertile F. serratus varied seasonally between 1.5 and 8.0 mol g-1 fresh wt h-1; in fertile plants the receptacle had a significantly lower respiratory rate than the vegetative tissue. The respiratory rate of the vegetative button of fertile H. elongata displayed less seasonal variation and was lower than that of the receptacle, which varied from a maximum of 9.5 mol g-1 fresh wt h-61 at receptacle initiation in October to a minimum of 2.0 mol g-1 fresh wt h-61 in February. The maximum photosynthetic rate (P(max)) of non-fertile plants of both species did not vary in a distinct seasonal manner (~60 mol G-1 fresh wt h-1 for F. serratus and ~12 mol g-1 fresh wt h-1 for H. elongata). In fertile plants, the P(max) of the receptacle tissue was (~50% lower in F. serratus, and at its peak three times higher in H. elongata, than that of vegetative tissue. The stable carbon-isotope ration (13 C) did not differ between different tissue types in F. serratus, but values did vary seasonally, being less negative in the summer than in the winter (-13.5‰ compared to -18‰). The receptacle tissue of H. elongata also displayed a distinct seasonal variation in 13C values (-12‰ in summer, -16‰ in winter), whilst the 13C of the vegetative button did not vary seasonally. The rate of uptake of inorganic nitrogen by the vegetative thallus was lower in H. elongata than in F. serratus. The receptacle tissue of F. serratus had lower uptake rates than the vegetative tissue, while the uptake rate by H. elongata receptacle tissue was higher than ...
A testable mechanism of CO2 accumulation in photolithotrophs, originally suggested by Pronina and Semenenko, is quantitatively analysed. The mechanism involves (as does the most widely accepted hypothesis) the delivery of HCO3- to the compartment containing Rubisco. It differs in proposing subsequent HCO3- entry (by passive uniport) to the thylakoid lumen, followed by carbonic anhydrase activity in the lumen; uncatalysed conversion of HCO3- to CO2, even at the low pH of the lumen, is at least 300 times too slow to account for the rate of inorganic C acquisition. Carbonic anhydrase converts the HCO3- to CO2 at the lower pH maintained in the illuminated thylakoid lumen by the light-driven H+ pump, generating CO2 at 10 times or more the thylakoid HCO3- concentration. Efflux of this CO2 can suppress Rubisco oxygenase activity and stimulate carboxylase activity in the stroma. This mechanism differs from the widely accepted hypotheses in the required location of carbonic anhydrase, i.e. in the thylakoid lumen rather than the stroma or pyrenoid, and in the need for HCO3- influx to thylakoids. The capacity for anion (assayed as Cl-) entry by passive uniport reported for thylakoid membranes is adequate for the proposed mechanism; if the Cl- channel dries not transport HCO3-, HCO~- entry could be by combination of the Cl- channel with a Cl- HCO3- antiporter. This mechanism is particularly appropriate for organisms which lack overt accumulation of total inorganic C in cells, but which nevertheless have the gas exchange characteristics of an organism with a CO2-concentrating mechanism.
Yin, ZH, Kaiser, WM, Heber, U & Raven, JA 1996, 'Acquisition and assimilation of gaseous ammonia as revealed by intracellular pH changes in leaves of higher plants', PLANTA, vol. 200, no. 4, pp. 380-387.
Raven, JA, Beardall, J, Johnston, AM, Kuebler, JE & Mcinroy, SG 1996, 'Inorganic carbon acquisition by Xiphophora chondrophylla (Phaeophyta, Fucales)', PHYCOLOGIA, vol. 35, no. 2, pp. 83-89.View/Download from: Publisher's site
Skene, KR, Kierans, M, Sprent, JI & Raven, JA 1996, 'Structural aspects of cluster root development and their possible significance for nutrient acquisition in Grevillea robusta (Proteaceae)', Annals of Botany, vol. 77, no. 5, pp. 443-452.View/Download from: Publisher's site
Light microscopy (LM), scanning (SEM) and transmission electron microscopy (TEM) were used to study structure and function of cluster roots in Grevillea robusta. These roots were developed during growth of G. robusta seedlings in modified Hoagland's solution lacking phosphate. Cluster rootlets formed root hairs, basipetally, only after completing their determinate development. The rootlet hairs branched in two ways and some had apical swelling Rootlets with hairs produced two different forms of exudate, one fibrous and the other globular in nature. The fibrous material appeared to he synthesised in the cortical cells. It is released by exocytosis from the epidermis Rootlet hairs produced only fibrous exudate. They attached firmly to pieces of vermiculite. The significance of cluster roots is discussed within the context of patchy soil resources.
Kübler, JE & Raven, JA 1996, 'Nonequilibrium rates of photosynthesis and respiration under dynamic light supply', Journal of Phycology, vol. 32, no. 6, pp. 963-969.View/Download from: Publisher's site
To identify processes that might account for differences in growth rates of rhodophytes under constant and dynamic light supply, we examined nonequilibrium gas exchanged by measuring time courses of photoinduction, loss of photoinduction, and respiration rates immediately after the light- dark transition. Using the rhodophyte species Palmaria palmata (Huds.) Lamour and Lomentaria articulata (Huds.) Lyngb., we compared the effects of growth- saturating constant photon flux density (PFD) (95 mol photons · m-2· s-1) to those of a dynamic light supply modeled on canopy movements in the intertidal zone (25 mol photons · m-2· s-1background PFD plus light flecks of 350 mol photons · m-2· s-1, 0.1 Hz). The time required for P. palmata and L. articulata to be fully photoinduced was not affected by the dynamics of light supply. L. articulata required only 6 min of illumination with either fluctuating or constant light to be completely induced compared to 20 min for P. palmata. The latter species also lost photoinduction more rapidly than did L. articulata in the dark. There was no significant decline in photoinduction state for either species at the background PFD. The time courses of respiration after illumination with constant and fluctuating light were significantly different for P. palmata but not for L. articulata when the total photon dose was equal. In general, gas exchange of P. palmata appeared to be particularly sensitive to the temporal distribution of light supply whereas that of L. articulata was sensitive to the amplitude of variations, being photoinhibited at high PFD. These results are discussed in terms of the different mechanisms of inorganic carbon acquisition in the two species.
Poole, I, Weyers, JDB, Lawson, T & Raven, JA 1996, 'Variations in stomatal density and index: Implications for palaeoclimatic reconstructions', Plant, Cell and Environment, vol. 19, no. 6, pp. 705-712.View/Download from: Publisher's site
The variation in stomatal characters in leaves from one Alnus glutinosa (L.) Gaertn. tree is analysed. Measurements were taken from over 70 sites on the abaxial surfaces of representative 'sun' and 'shade' leaves having the same insertion point. The mean values of stomatal density and index in the shade leaf were significantly lower (71 and 93%, respectively) than those for the sun leaf. Within leaves, up to 2.5-fold differences in stomatal density values were observed. Contour maps derived from the data reveal non-random trends over the leaf surface. Correlations between stomatal density, epidermal cell density and stomatal index indicate that the variation in stomatal density within leaves arose primarily from local differences in stomatal differentiation, rather than from local differences in leaf expansion. This research demonstrates that a high level of variation in stomatal characters occurs both within and between leaves. We conclude that a well-defined sampling strategy should be used when estimating stomatal characters for (tree) leaves. Furthermore, the leafs insertion point and situation within the tree crown should be taken into account. We discuss the implications of these findings for palaeoclimatic interpretations and emphasize the need for great caution when drawing conclusions based solely on stomatal characters.
Korb, RE, Raven, JA, Johnston, AM & Leftley, JW 1996, 'Effects of cell size and specific growth rate on stable carbon isotope discrimination by two species of marine diatom', MARINE ECOLOGY PROGRESS SERIES, vol. 143, no. 1-3, pp. 283-288.View/Download from: Publisher's site
Raven, JA 1996, 'The bigger the fewer: Size, taxonomic diversity and the range of chlorophyll(ide) pigments in oxygen-evolving marine photolithotrophs', Journal of the Marine Biological Association of the United Kingdom, vol. 76, no. 1, pp. 211-217.
There is a greater diversity of spectrally distinct chlorophyll(ide) pigments in individuals of many of the large number of higher taxa of marine oxygen-evolvers which contain only small organisms than in those few higher taxa which also (or only) have large-sized organisms. The occurrence of more types of pigment in smaller organisms can be mechanistically related to the lesser degree of self-shading in smaller organisms, thus allowing spectral diversity to be reflected in enhanced photon absorption from a given light field as a result of multiple spectral forms of chlorophyll(ide)s. This provides a mechanistic basis with ecological significance for the greater chlorophyll(ide) diversity in small marine O2-evolvers which show greater biodiversity at the level of higher taxa than do classes or divisions which are comprised only, or predominantly, of macrophytes (Ulvophyceae, Rhodophyta, Phaetophyta, seagrasses).
Johnston, AM & Raven, JA 1996, 'Inorganic carbon accumulation by the marine diatom phaeodactylum tricornutum', European Journal of Phycology, vol. 31, no. 3, pp. 285-290.View/Download from: Publisher's site
The ability of the diatom Phaeodactylum tricornutum to accumulate inorganic carbon was investigated using the silicone oil centrifugation technique. At internal inorganic carbon concentrations less than 0.2 mol m-3 the internal inorganic carbon concentration was always greater than expected assuming CO2 assimilation based on diffusion. When tested at 2.0 mol m-3, the normal inorganic carbon concentration of seawater, the internal inorganic carbon concentration was less than the external concentration. Apparently this alga has the ability to accumulate inorganic carbon. When grown in poorly aerated media P. tricornutum is able to reduce the inorganic carbon concentration of the media to a greater extent than during growth in well-aerated media. Cells that have experienced inorganic carbon depletion are able to accumulate inorganic carbon to a greater extent than cells from well-aerated cultures when tested at low external inorganic carbon concentrations. Inorganic carbon photosynthesis dose-response curves showed that carbon-depleted cells have a higher affinity for inorganic carbon than cells from well-aerated cultures. 13C values of carbon-depleted cultures were less negative than those of well-aerated cultures. These results are discussed in relation to previously reported inorganic carbon-photosynthesis dose-response curves. This alga is able to alter the mechanism of inorganic carbon acquisition in response to changes in the external inorganic carbon concentration. © 1996 The British Phycological Society.
Allen, JF & Raven, JA 1996, 'Free-radical-induced mutation vs redox regulation: costs and benefits of genes in organelles.', Journal of molecular evolution, vol. 42, no. 5, pp. 482-492.View/Download from: Publisher's site
The great majority of the CO2fixed by marine (freshwater and terrestrial) autotrophs involves Rubisco (Fuchs, 1989; Raven, 1991a,b). Generally, in marine autotrophs Rubisco is the sole carboxylase involved in converting exogenous inorganic C into at least 95% of cellular organic C. Thus, there are very few organisms in the sea with C4or CAM mechanisms which interpose (C3+ C1) carboxylation and (C4- C1) decarboxylation reactions between external inorganic C and Rubisco (and hence the great bulk of organic C in the organism). Furthermore, only a small number of species of microscopic marine autotrophs use non-Rubisco systems for the bulk of their inorganic C acquisition, e.g. those using the reductive tricarboxylic acid cycle and the reductive acetyl CoA pathway (Fuchs, 1989), and they account for a very small fraction of the total marine inorganic C reduction in biological processes. However, there are important roles for carboxylases other than Rubisco in autotrophs which have no carboxylase other than Rubisco involved in acquiring at least 95% of their total C. This is because certain compounds (e.g. tetrapyrrols) cannot be produced in most autotrophs without a (C3+ C1) carboxylation to give net production of the glutamate needed to produce pyrrol monomers. Non-Rubisco carboxylations are also involved in other essential biosyntheses e.g. of citrulline and arginine, of purines and (without inorganic C retention for more that a second) lipid synthesis (see Raven and Farquhar, 1990; Raven, 1995a). It must be emphasised that these non-Rubisco carboxylases only account for < 5% of the C retained by these organisms. Having seen how predominant Rubisco is in the conversion of inorganic C to reduced organic C in oceanic autotrophs, we consider the phylogeny of Rubisco.
KUBLER, JE & RAVEN, JA 1995, 'THE INTERACTION BETWEEN INORGANIC CARBON ACQUISITION AND LIGHT SUPPLY IN PALMARIA-PALMATA (RHODOPHYTA)', JOURNAL OF PHYCOLOGY, vol. 31, no. 3, pp. 369-375.View/Download from: Publisher's site
Primary producers in aquatic environments cover a range of living biomasses from 1013 to 104 g dw. Benthic plants at the high end of this range contribute 5 Gt C year,1 to global primary productivity. Plankton at the lower end (up to 104 g dw) contributes about 30 Gt C year1. While many problems of interpretation remain, in general terms the size of the organisms which dominate particular habitats can be related to the physics of water movement and its interaction with the availability of light and nutrients, the generation time of the organism, and the attentions of grazers. A second scaling problem is that of methods of studying the global energy flow and nutrient cycling roles of aquatic primary producers. Problems with scaling up from smallscale and mesoscale to regional or global scale, and the prospects of more direct estimates of largescale productivity, are discussed. Copyright © 1995, Wiley Blackwell. All rights reserved
RAVEN, JA, JOHNSTON, AM, NEWMAN, JR & SCRIMGEOUR, CM 1994, 'Inorganic carbon acquisition by aquatic photolithoatrophs of the Dighty Burn, Angus, U.K.: uses and limitations of natural abundance measurements of carbon isotopes', New Phytologist, vol. 127, no. 2, pp. 271-286.View/Download from: Publisher's site
The 13C/12C ratio (expressed as 13C) of benrhic photolithotrophs. in the Dighn Water (= Burn) were measured fur comparison with that of the potential inorganic carhun sources. CO2 and HCO3, in the Burn. The Burn water contains an average of 65.7 mmol m3 CO2 with 13C of 14.7% and 1600 mmol m3 HCO3 with 13C of 4.%. 13C values of riparian vegetation were also measured as contributors, after respiration in the soil or the Burn, to the 13C of inorganic carbon in the Burn. The potential range of differences in 13C/12C between dissolved CO2 and plant organic C is set by the intrinsic 13c/12C discrimination ( value) in CO2 fixation by Rubisco. Main results and conclusions are. as follows, (i) A literature survey suggests that there is no convincing evidence that the , Values (rate constant for 12CO2 fixation relative to that for 13CO2 fixation by Rubisco in the absence of CO2 transport limitation) for the'lower plants'in the Burn (diatoms, green and red algae, mosses) are significantly different from the wellestablished p values for the flowering plum enzyme. (ii) In confirmation of earlier work, the semierect 'streamer'gametophytes of the red alga Lemanea mamillosa and the moss Fontinalis antipyetica have 13C values which can only be interpreted in terms of diffusive CO2 entry with minimal limitation of photosynthesis by CO diffusion, (iii) The seruierect grren alga Cladophora glomerata and the flowering plant Ranunculus penicillatus ssp. pseudofluitons (formerly var. calcareus) are both able to use HCO3. Their 13C values indicate that, if the HCO3 use system does not (as is likely) discriminate significantly between 13C and 12C, then a substantial fraction of the inorganic C made available to Rubisco must return to the medium, carrying 13Cinorganic C not fixed by Rubisco. (iv) Two sets of 13C data from different hydrodynamic regimes distance from leading edge of a flat stone; different size of thalli) show that the attainable differences in si...
Handley, LL, Nevo, E, Raven, JA, Martinez-carrasco, R, Scrimgeour, CM, Pakniyat, H & Forster, BP 1994, 'Chromosome 4 controls potential water use efficiency (13C) in barley', Journal of Experimental Botany, vol. 45, no. 11, pp. 1661-1663.View/Download from: Publisher's site
By combining the approaches of whole-shoot carbon discrimination and genetic analysis, we found that chromosome 4 controls potential water use efficiency (13C) in barley. In a simultaneous experiment, 13C of 19 wild barley populations from Israel were grown under well-watered conditions in Scotland. Populations originating at the most arid sites had the most negative 13C, hence the lowest potential water use efficiency. © 1994 Oxford University Press.
Raven, JA, Johnston, AM, Parsons, R & Kübler, J 1994, 'The influence of natural and experimental high O2 concentrations on O2-evolving phototrophs', Biological Reviews of the Cambridge Philosophical Society, vol. 69, no. 1, pp. 61-94.
MARTINSLOUCAO, MA, WOLLENWEBER, B & RAVEN, JA 1993, 'RESPONSE OF SALVINIA SPP TO DIFFERENT NITROGEN-SOURCES - THE ACID-BASE REGULATION APPROACH', OECOLOGIA, vol. 93, no. 4, pp. 524-530.View/Download from: Publisher's site
RAVEN, JA 1993, 'THE EVOLUTION OF VASCULAR PLANTS IN RELATION TO QUANTITATIVE FUNCTIONING OF DEAD WATER-CONDUCTING CELLS AND STOMATA', BIOLOGICAL REVIEWS, vol. 68, no. 3, pp. 337-363.View/Download from: Publisher's site
Raven, JA, Johnston, AM & Turpin, DH 1993, 'Influence of changes in CO2 concentration and temperature on marine phytoplankton 13C/12C ratios: an analysis of possible mechanisms', Global and Planetary Change, vol. 8, no. 1-2, pp. 1-12.View/Download from: Publisher's site
The 13C/12C fractionation associated with net transport fluxes and chemical conversions, and with equilibria, associated with inorganic C assimilation processes in marine phytoplankton are quite well understood, though some gaps remain. These values are used in models of overall 13C/12C fractionation in inorganic C assimilation involving the two major mechanisms involved in inorganic C entry, i.e. diffusion of CO2 and active transport of CO2 and/or HCO3-. The CO2 diffusion model predicts the observed decrease in the 13C/12C of plankton organic C relative to source CO2 when CO2 concentration increases and/or temperature decreases. The inorganic C active transport model is complicated by repression of the active transport mechanism at high inorganic C levels, but this model also predicts the observed effect on cell 13C/12C of changes in CO2 partial pressure or temperature for cell growth. More refined modelling and more input data are needed for both transport processes. Operation of either of the alternative mechanisms for inorganic C entry can be consistent with growth rate not being limited by inorganic C supply even when the photosynthetic rate is inorganic C-limited. © 1993.
PARSONS, R, RAVEN, JA & SPRENT, JI 1992, 'A SIMPLE OPEN FLOW SYSTEM USED TO MEASURE ACETYLENE-REDUCTION ACTIVITY OF SESBANIA-ROSTRATA STEM AND ROOT-NODULES', JOURNAL OF EXPERIMENTAL BOTANY, vol. 43, no. 250, pp. 595-604.View/Download from: Publisher's site
RAVEN, JA 1992, 'PRESENT AND POTENTIAL USES OF THE NATURAL ABUNDANCE OF STABLE ISOTOPES IN PLANT-SCIENCE, WITH ILLUSTRATIONS FROM THE MARINE-ENVIRONMENT', PLANT CELL AND ENVIRONMENT, vol. 15, no. 9, pp. 1083-1091.View/Download from: Publisher's site
RAVEN, JA 1991, 'RESPONSES OF AQUATIC PHOTOSYNTHETIC ORGANISMS TO INCREASED SOLAR UVB', JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY, vol. 9, no. 2, pp. 239-244.View/Download from: Publisher's site
Raven, JA 1991, 'Plant responses to high O-2 concentrations: relevance to previous high O-2 episodes', PALAEOGEOGRAPHY PALAEOCLIMATOLOGY PALAEOECOLOGY, vol. 97, no. 1-2, pp. 19-38.View/Download from: Publisher's site
Exposure to the 43 kPa O2 thouhht to correspond to the highest O2 partial pressure in the Phanerozoic rather than the 21 kPa in the present atmosphere deleteriously affects extant C3 land plants by increasing (1) the O2 inhibition (competitive with CO2) of the carboxylating enzyme ribulose 1,5 bisphosphate carboxylase-oxygenase, (2) the O2 inactivation of nitrogenase in symbiotic N2-fixers, and (3) the generation of reactive oxygen species which can damage nuclei acids, proteins, lipids and other cell constituents. Exposure of these plants to O2 levels approximating a high O2 episode inhibits growth via inhibition of ribulose carboxylase and, possibly, by unrepaired damage caused by reactive oxygen species and by the resource diversion related to increasing the capacity of mechanisms reducing the level of reactive oxygen species and to repairing the damage caused by these species. Longer term effects (e.g. increased level of mutations in a population) have not been explored. Natural exposure of all or part of extant plants to O2 levels in excess of 43 kPa occurs in the light in most plants other than C3 land plants due to photosynthetic O2 evolution with restricted diffusion to a medium with normal O2 levels attendant on the maintenance of high CO2 concentrations around ribulose 1,5 bisphosphate carboxylase. While the high O2 levels seem to be restricted where possible to non-meristematic regions of multicellular plants, these plants which have high internal O2 levels do not seem to be disadvantaged relative to C3 land plants. The high O2 concentrations proposed for periods in the Phanerozoic are tolerated, as intracellular O2 levels, in some cells of a substantial fraction of extant phototrophs, and many can tolerate substantially higher levels. Fire seems more likely than the effects discussed in this paper as limitations on co-occurence of terrestrial vegetation and high O2 levels. © 1991.
RAVEN, JA & JOHNSTON, AM 1991, 'PHOTOSYNTHETIC INORGANIC CARBON ASSIMILATION BY PRASIOLA-STIPITATA (PRASIOLALES, CHLOROPHYTA) UNDER EMERSED AND SUBMERSED CONDITIONS - RELATIONSHIP TO THE TAXONOMY OF PRASIOLA', BRITISH PHYCOLOGICAL JOURNAL, vol. 26, no. 3, pp. 247-257.View/Download from: Publisher's site
SURIF, MB & RAVEN, JA 1990, 'PHOTOSYNTHETIC GAS-EXCHANGE UNDER EMERSED CONDITIONS IN EULITTORAL AND NORMALLY SUBMERSED MEMBERS OF THE FUCALES AND THE LAMINARIALES - INTERPRETATION IN RELATION TO C-ISOTOPE RATIO AND N-ISOTOPE AND WATER-USE EFFICIENCY', OECOLOGIA, vol. 82, no. 1, pp. 68-80.View/Download from: Publisher's site
JOHNSTON, AM & RAVEN, JA 1990, 'EFFECTS OF CULTURE IN HIGH CO2 ON THE PHOTOSYNTHETIC PHYSIOLOGY OF FUCUS-SERRATUS', BRITISH PHYCOLOGICAL JOURNAL, vol. 25, no. 1, pp. 75-82.View/Download from: Publisher's site
SURIF, MB & RAVEN, JA 1989, 'EXOGENOUS INORGANIC CARBON-SOURCES FOR PHOTOSYNTHESIS IN SEAWATER BY MEMBERS OF THE FUCALES AND THE LAMINARIALES (PHAEOPHYTA) - ECOLOGICAL AND TAXONOMIC IMPLICATIONS', OECOLOGIA, vol. 78, no. 1, pp. 97-105.View/Download from: Publisher's site
MACFARLANE, JJ & RAVEN, JA 1989, 'QUANTITATIVE-DETERMINATION OF THE UNSTIRRED LAYER PERMEABILITY AND KINETIC-PARAMETERS OF RUBISCO IN LEMANEA-MAMILLOSA', JOURNAL OF EXPERIMENTAL BOTANY, vol. 40, no. 212, pp. 321-327.View/Download from: Publisher's site
This chapter discusses the transport systems in algae and bryophytes. Giant-celled algae were of great importance in developing many techniques for the study of (and the hypotheses of the mechanism of) membrane transport in plants and in biological material in general. They, as well as smaller-celled algae and bryophytes, will prove useful in the analyses of general membrane transport phenomena as well as of specifically plant processes. Further advances in the use of algae and bryophytes in general membrane transport studies require that their demonstrated utility in relation to perfusion, voltage-clamp, and (radio) chemical tracer studies be integrated with the genetic, biochemical, and patch-clamp techniques developed for other groups of organisms. Such integration would also greatly benefit the studies of membrane transport in algae and bryophytes in relation to studies of the structure, physiology, and ecology of the organisms. © 1989, Elsevier Inc. All rights reserved.
Raven, JA & Reed, RH 1989, 'Abstracts of papers read at the winter meeting at the university of sheffield, 3-5 january 1989', British Phycological Journal, vol. 24, no. 3, pp. 297-315.View/Download from: Publisher's site
RAVEN, JA & SAMUELSSON, G 1988, 'ECOPHYSIOLOGY OF FUCUS-VESICULOSUS L CLOSE TO ITS NORTHERN LIMIT IN THE GULF OF BOTHNIA', BOTANICA MARINA, vol. 31, no. 5, pp. 399-410.View/Download from: Publisher's site
Osborne, BA & Raven, JA 1986, 'Growth light level and photon absorption by cells of chlamydomonas rheinhardii, dunaliella tertiolecta (Chlorophyceae, volvocales), scenedesmus obliquus (chlorophyceae, chlorococcales) and euglena viridis (euglenophyceae, euglenales)', British Phycological Journal, vol. 21, no. 3, pp. 303-313.View/Download from: Publisher's site
Reductions in the growth light level (40 to 6 pmol m-2 s-1) resulted in increases in chlorophyll and protein per cell for all of the species examined. Only Dunaliella tertiolecta exhibited a reduction in chlorophyll a:b ratio with decreases in the photon flux density. However, the specific absorption coefficient (af) normalized to chlorophyll a (aa*) remained invariant for all of the microalgae studied. Constant values for the specific absorption coefficient normalized to the total pigment content (a*a+b) were also found for the species Chlamydomonas rheinhardii, Euglena viridis and Scenedesmus obliquus. In contrast a*a+b for D. tertiolecta decreased with a reduction in light level due to an increase in the proportion of chlorophyll b. Differences in ai* were related to cell size and pigment content and possible reasons for the constancy of aa* discussed. Increases in the absorption cross sections (sQa were also found at reduced light levels due to an increase in the absorptance per cell (acell). The lower acel] for D. tertiolecta, compared with C. rheinhardii was exactly compensated for by a larger light-capturing area. Although the increase in acell does not compensate for the reduction in the incident light level, it does reduce this range by half on an absorbed light basis. © 1986 Taylor & Francis Group, LLC.
MACFARLANE, JJ & RAVEN, JA 1985, 'EXTERNAL AND INTERNAL CO2 TRANSPORT IN LEMANEA - INTERACTIONS WITH THE KINETICS OF RIBULOSE BISPHOSPHATE CARBOXYLASE', JOURNAL OF EXPERIMENTAL BOTANY, vol. 36, no. 165, pp. 610-622.View/Download from: Publisher's site
ALLEN, S, RAVEN, JA & THOMAS, GE 1985, 'ONTOGENETIC CHANGES IN THE CHEMICAL-COMPOSITION OF RICINUS-COMMUNIS GROWN WITH NO3(-) OR NH4(+) AS N-SOURCE', JOURNAL OF EXPERIMENTAL BOTANY, vol. 36, no. 164, pp. 413-425.View/Download from: Publisher's site
ANDREWS, M, BOX, R, FYSON, A & RAVEN, JA 1984, 'Source—sink characteristics of carbon transport in Chara hispida', Plant, Cell & Environment, vol. 7, no. 9, pp. 683-687.View/Download from: Publisher's site
Abstract Rates of uptake of 14Clabelled inorganic carbon were measured for whole Chara hispida plants, detached parts of the shoot and isolated (splitchamber technique) apices, lateral branchlets and rhizoid—node complexes. The rates of inorganic carbon uptake by the rhizoid—node complex expressed per gram fresh weight whole plant were three to four orders of magnitude less than the uptake for the whole plant. Up to 70% of the carbon taken up by the rhizoid—node complex was translocated to the shoot. After 12 h exposure to 14Clabelled inorganic carbon the concentration of 14C was greater in apices than in uppermost or central internodal cells and in all lateral branchlets, regardless of whether label was supplied to the whole plant or isolated rhizoid—node complexes. Measurement of inorganic carbon uptake by detached internodal cells and detached and isolated apices and lateral branchlets showed that lateral branchlets had the greatest rates of inorganic carbon uptake. During 12 h exposure to 14C, isolated lateral branchlets translocated to the attached shoot 55% of the labelled carbon taken up; for isolated apices this value was only 13%. It is concluded that it is highly unlikely that the rhizoid of Chara hispida could acquire a significant fraction of the whole plant requirement for inorganic carbon and that apices are sink regions for photosynthate while lateral branchlets are source regions. Copyright © 1984, Wiley Blackwell. All rights reserved
RICHARDSON, K, GRIFFITHS, H, REED, ML, RAVEN, JA & GRIFFITHS, NM 1984, 'INORGANIC CARBON ASSIMILATION IN THE ISOETIDS, ISOETES-LACUSTRIS L AND LOBELIA-DORTMANNA L', OECOLOGIA, vol. 61, no. 1, pp. 115-121.View/Download from: Publisher's site
BOX, R, ANDREWS, M & RAVEN, JA 1984, 'INTERCELLULAR TRANSPORT AND CYTOPLASMIC STREAMING IN CHARA-HISPIDA', JOURNAL OF EXPERIMENTAL BOTANY, vol. 35, no. 156, pp. 1016-1021.View/Download from: Publisher's site
Culture conditions that support high growth rates of Chara hispida L and Nitella flexilis (L.) Ag. are described. The optimum conditions for both rhizoid and shoot growth are obtained using a substrate of 425-710 pm sand particles and a solution of inorganic salts in distilled water. The highest rates of linear extension and dry weight increase of shoots are obtained with sand substrates less than 710 pm in size. © 1984 British Phycological Society.
RAVEN, J, BEARDALL, J & GRIFFITHS, H 1982, 'INORGANIC C-SOURCES FOR LEMANEA, CLADOPHORA AND RANUNCULUS IN A FAST-FLOWING STREAM - MEASUREMENTS OF GAS-EXCHANGE AND OF CARBON ISOTOPE RATIO AND THEIR ECOLOGICAL IMPLICATIONS', OECOLOGIA, vol. 53, no. 1, pp. 68-78.View/Download from: Publisher's site
RAVEN, JA & BEARDALL, J 1982, 'THE LOWER LIMIT OF PHOTON FLUENCE RATE FOR PHOTOTROPIC GROWTH - THE SIGNIFICANCE OF SLIPPAGE REACTIONS', PLANT CELL AND ENVIRONMENT, vol. 5, no. 2, pp. 117-124.View/Download from: Publisher's site
BEARDALL, J, GRIFFITHS, H & RAVEN, JA 1982, 'CARBON ISOTOPE DISCRIMINATION AND THE CO2 ACCUMULATING MECHANISM IN CHLORELLA-EMERSONII', JOURNAL OF EXPERIMENTAL BOTANY, vol. 33, no. 135, pp. 729-737.View/Download from: Publisher's site
Raven, JA & Beardall, J 1981, 'The intrinsic permeability of biological membranes to H+: Significance for the efficiency of low rates of energy transformation', FEMS Microbiology Letters, vol. 10, no. 1, pp. 1-5.View/Download from: Publisher's site
Raven, JA & Beardall, J 1981, 'Carbon dioxide as the exogenous inorganic carbon source for batrachospermum and lem an e a', British Phycological Journal, vol. 16, no. 2, pp. 165-175.View/Download from: Publisher's site
Rates of photosynthesis at light saturation as a function of CO2 concentration and rates of dark respiration, are reported for the freshwater red algae Lemanea mamillosa and Batracho- spermum sp., and are related to their ecological strategies. The CO2 compensation concentration in these two algae is pH-independent in the range pH 6.5-8.9, and is of a magnitude which suggests that these algae are unable to use HCO3'in photosynthesis, and lack a 'CO2 concentrating mechanism'. This is related to the relatively high CO2/HCO3 ratio in the natural habitats of the algae, in contrast with the seawater in which most rhodophytes live and in which some red algae exhibit characteristics of HCO3 'use. The absence of HCO2 use is also discussed in relation to the 'bipolar band growth' of florideophytes, and to the relative availability of C, N and P and light in these haptophytic algae. © 1981 Taylor & Francis Group, LLC.
RAVEN, JA & SMITH, FA 1980, 'INTRACELLULAR PH REGULATION IN THE GIANT-CELLED MARINE ALGA CHAETOMORPHA-DARWINII', JOURNAL OF EXPERIMENTAL BOTANY, vol. 31, no. 124, pp. 1357-1369.View/Download from: Publisher's site
DEMICHELIS, MI, RAVEN, JA & JAYASURIYA, HD 1979, 'MEASUREMENT OF CYTOPLASMIC PH BY THE DMO TECHNIQUE IN HYDRODICTYON-AFRICANUM', JOURNAL OF EXPERIMENTAL BOTANY, vol. 30, no. 117, pp. 681-695.View/Download from: Publisher's site
SMITH, FA, RAVEN, JA & JAYASURIYA, HD 1978, 'UPTAKE OF METHYLAMMONIUM IONS BY HYDRODICTYON-AFRICANUM', JOURNAL OF EXPERIMENTAL BOTANY, vol. 29, no. 108, pp. 121-133.View/Download from: Publisher's site
Raven, JA 1977, 'The Evolution of Vascular Land Plants in Relation to Supracellular Transport Processes', Advances in Botanical Research, vol. 5, no. C, pp. 153-219.View/Download from: Publisher's site
This chapter describes several aspects of the significance of transport processes in the evolution of vascular land plants from their putative ancestors—the green algae. The vascular land plants have, in addition to the transport processes at the cell level, which are common to all organisms, important transport processes at the supracellular level, which involve complex anatomical features. The homoiohydric vascular land plant has three major transport systems at the supracellular level—the apoplast, the symplast, and the intercellular gas space system. The aquatic green algal ancestors of these plants use only the symplast for transport at the supracellular level. The other two transport systems, together with the elaboration of the symplast into the much more efficient phloem, are essential components of the homoiohydric land plants. © 1977, Academic Press Inc. (London) Ltd.
Raven, JA 1976, 'The quantitative role of 'dark' respiratory processes in heterotrophic and photolithotrophic plant growth', Annals of Botany, vol. 40, no. 3, pp. 587-602.
The hypothesis that ATP and reductant generated in photosynthetic partial reactions can be used in vivo for energy-requiring reactions other than the photosynthetic carbon reduction cycle is supported by much experimental evidence. When such direct use of photo-produced cofactors occurs, it might be expected that the alternative source of ATP and reductant, i.e. 'dark' respiration, occurs to a smaller extent than in heterotrophic cells. This paper uses data from the literature to compute the CO2/C ratio (CO2produced in 'dark' respiration processes per C incorporated into cell material) for photolithotrophic and heterotrophic growth of a range of unicellular algae and angiosperms. The minimum CO2/C value observed for heterotrophic growth is similar to, but rather higher than, that calculated using the stoichiometry of known respiratory, biosynthetic and transport reactions for the conversion of carbohydrate and the supplied minerals into a plant of the appropriate composition. However, for unicellular algae the CO2/C for photolithotrophic growth is much lower than either of these values for the heterotrophic CO2/C value, and strongly supports the view that the direct use of photo-produced cofactors for processes other than the photosynthetic carbon reduction cycle is an important aspect of energy metabolism in these organisms. The minimum CO2/C observed is similar to that predicted when dark respiratory reactions serve only to produce essential C skeletons. For angiosperms, the evidence is more equivocal, but is consistent with some direct use of photo-produced cofactors for processes other than CO2fixation. The spatial separation of energy-requiring processes from chloroplasts could partly account for this smaller emphasis on nonrespiratory energy supply to processes other than CO2fixation in angiosperms compared with unicellular algae. © 1976 Annals of Botany Company.
Glidewell, SM & Raven, JA 1976, 'Photorespiration: Ribulose diphosphate oxygenase or hydrogen peroxide?', Journal of Experimental Botany, vol. 27, no. 2, pp. 200-204.View/Download from: Publisher's site
Oxygen uptake and evolution in illuminated cells of Hydrodictyon qfricanum have been measured using 18O2 mass spectrometry. Earlier work showed that the light-stimulated O2 uptake under conditions of light and CO2 saturation was insensitive to cyanide and to CCCP. This was interpreted as due to a pseudocyclic electron flow, possibly associated with glycolate synthesis by the pathway proposed by Coombs and Whittingham. The work reported here was carried out at the CO2 compensation point, where light-dependent O2 uptake is higher than at CO2 saturation. The component of O2 uptake which is stimulated by lowering the CO2 concentration is inhibited by either cyanide or CCCP. This component is attributed to the activity of ribulose diphosphate (RuDP) oxygenase, which is completely inhibited by CO2 at high CO2 levels. The rate of pseudocyclic electron flow seems to be insensitive to changes in CO2 concentration between saturation and the compensation point © 1976 Oxford University Press.
RAVEN, JA 1975, 'TRANSPORT OF INDOLEACETIC-ACID IN PLANT-CELLS IN RELATION TO PH AND ELECTRICAL POTENTIAL GRADIENTS, AND ITS SIGNIFICANCE FOR POLAR IAA TRANSPORT', NEW PHYTOLOGIST, vol. 74, no. 2, pp. 163-172.View/Download from: Publisher's site
RAVEN, JA & GLIDEWELL, SM 1975, 'EFFECTS OF CCCP ON PHOTOSYNTHESIS AND ON ACTIVE AND PASSIVE CHLORIDE TRANSPORT AT PLASMALEMMA OF HYDRODICTYON-AFRICANUM', NEW PHYTOLOGIST, vol. 75, no. 2, pp. 205-213.View/Download from: Publisher's site
RAVEN, JA & GLIDEWELL, SM 1975, 'SOURCES OF ATP FOR ACTIVE PHOSPHATE TRANSPORT IN HYDRODICTYON-AFRICANUM - EVIDENCE FOR PSEUDOCYCLIC PHOTOPHOSPHORYLATION INVIVO', NEW PHYTOLOGIST, vol. 75, no. 2, pp. 197-204.View/Download from: Publisher's site
Glidewell, SM & Raven, JA 1975, 'Measurement of simultaneous oxygen evolution and uptake in Hydrodictyon Africanum', Journal of Experimental Botany, vol. 26, no. 4, pp. 479-488.View/Download from: Publisher's site
Oxygen uptake and evolution in illuminated and darkened cells of Hydrodictyon Africanum have been measured using 18O2 mass speetrometry. Under conditions of light and CO2 saturation for photosynthesis, light stimulates oxygen uptake more than two-fold. This stimulation is prevented by DCMU but is not affected by cyanide or the uncoupler CCCP. The data are consistent with the occurrence of a pseudocyclic electron flow and photophosphorylation in vivo in H. Africanum; this agrees with data on light-dependent active phosphate influx in this alga. Part of the light-stimulated oxygen uptake might be involved in glycolate synthesis by the pathway proposed by Coombs and Whittingham. © 1975 Oxford University Press.
The energy source for active phosphate influx in Hydrodictyon Africanum has been investigated using gas mixtures with and without O2 and CO2, light of various wavelengths, and metabolic inhibitors selective for respiratory or photosynthetic electron transport and phosphorylation. It is concluded that, as in the other green algae studied, active phosphate transport requires ATP. In the dark this is supplied by oxidative phosphorylation; in the light the influx is much less sensitive to inhibition of oxidative phosphorylation, and photophosphorylation (including cyclic photophosphorylation) can act as energy source. This situation is more like that for active K influx (coupled to active Na efflux) than to active Cl influx in H. Africanum, except that the active dark influx is relatively greater for phosphate influx. The significance of these results for the mechanism of regulation of light-stimulated ATP-requiring processes, and for the role of photosynthetic and oxidative phosphorylation in the energy metabolism of green cells, is discussed. © 1974 Oxford University Press.
The quantity of CO2 arising from photorespiration in angiosperms and in algae has been estimated. Much of such CO2 arises from the metabolism of glycolate so that estimates are based on the rate of formation of glycolate and the rate at which it is metabolized (Table 1). The total CO2 production in leaves or algae in the light can then be taken as equal to the photorespiratory CO2 plus the CO2 produced by'dark' respiratory pathways. Methods of estimating CO2 release from illuminated green tissues are considered and the rate of decarboxylation deduced from biochemical evidence of substrate turnover is compared with the observed rate of CO2 release; the difference between these values is reassimilation (Table 1). In angiosperms with the PGA pathway, in air, reassimilation is never complete and ranges from o to 0.6 of the endogenous CO2 production. This implies that the resistance to refixation is as great or greater than the resistance to loss of endogenous CO2 to the medium and is in accord with the relative values of these resistances based on other evidence. In law oxygen environment less glycolate is produced and hence less photorespiratory CO2; the resistance to refixation is smaller and so fractional reassimilation in increased. Unicellular algae have the PGA pathway and some appear to have more efficient reassimilation than the corresponding angiosperms. The special problems of metabolism in four carbon acid plants are discussed. Such plants show essentially complete reassimilation since they do not lose CO2 when illuminated. In their leaves the resistance to escape of endogenously produced CO2 must be very much greater than the resistance to refixation. The low resistance to refixation is probably related to high levels of CO2 in chloroplasts which are generated by the'CO2pump' rather than to any peculiarities of carboxydismutase. The importance of reassimilation is discussed in relation to the influence of CO2 on various aspects of metabolism, to isotopic...
Larkum, A, Szabo, M, Fitzpatrick, D & Raven, J 2017, 'Cyclic Electron Flow in Cyanobacteria and Eukaryotic Algae' in Photosynthesis and Bioenergetics, World Scientific, pp. 305-343.View/Download from: UTS OPUS or Publisher's site
In oxygenic photosynthesis light energy is largely captured in linear electron flow (LEF) between the photosystems and drives ATP formation via a thylakoid proton-driven ATP synthase. In addition, for over 50 years there has been good evidence that an additional cyclic electron flow (CEF) around photosystem I (PSI) is harnessed to provide extra ATP in addition to that produced by LEF. The evidence comes from all oxygenic organisms, cyanobacteria, eukaryotic algae and embryophytic plants. However, the CEF mechanism has been difficult to investigate because of the cyclic nature of the EF and confusion with other pathways not using oxygen as a terminal electron acceptor, and the MAPS, flavodiiron and chlororespiration pathways to oxygen. This article discusses the current evidence for CEF in all oxygenic organisms and suggests future experiments by which the situation can be clarified.
© 2012 Springer Science+Business Media B.V. All rights reserved. Summary: All cyanobacteria are actually or potentially photolithotrophic, with the exception of a recently discovered non-auotrophic free-living diazotroph which is presumably a (photo-)organotroph. Photolithotrophy involves CO 2 assimilation by Form 1A or Form 1B Rubiscos with low affinity for CO 2 and a small discrimination between CO 2 and O 2 and, at present CO 2 levels, invariably involves an inorganic carbon concentrating mechanism (CCM). About half of the cyanobacterial strains tested are facultatively photo-organotrophic, a few of which are also facultative chemo-organotrophs; the rest are obligate photolithotrophs. In the natural environment the best-established cases of photo- or chemo-organotrophy are in symbioses of diazotrophic cyanobacteria with organisms that are already photosynthetic. The quantitative contribution of dissolved organic matter to otherwise photolithotrophically growing cyanobacteria is unclear. Extent cyanobacteria are involved in both biologically mediated calcification (direct role of the organism) and biologically related calcification (indirect role of the organism). The timing of the evolution of cyanobacterial CCM is unclear: the CCM probably evolved in low-CO 2 episodes in the late Neoproterozoic or the Carboniferous, with spread to all cyanobacteria in the already established major clades by horizontal gene transfer. Cyanobacteria may be the last surviving photolithotrophs as the sun emits more energy and (by whatever mechanism) there is a decreased greenhouse gas, including CO 2 , content, of the atmosphere.
Raven, JA, Roberts, K, Granum, E & Leegood, RC 2008, 'The ecology and evolution of single-cell C4-like photosynthesis in diatoms: Relevance to C4 rice' in Charting New Pathways to C4 Rice, pp. 297-314.View/Download from: Publisher's site
© International Rice Research Institute 2008. The 10,000 or more species of diatoms are microscopic photosynthetic organisms of the class Bacillariophyceae in the phylum H+eterokontophyta. They are dominant primary producers in marine and inland water habitats, and may account for up to 20% of global primary productivity. The core carboxylation enzyme in their photosynthesis is Form ID Rubisco (ribulose bisphosphate carboxylase-oxygenase), which, if it replaced rice Form IB Rubisco on a molecule- for-molecule basis, would give slightly lower rates of photosynthesis at extant CO2 concentrations. These kinetic characteristics, along with the low conductance for CO2 of aqueous boundary layers, rationalize the occurrence of CCMs (inorganic carbon-concentrating mechanisms) in all diatoms investigated. It was assumed that these mechanisms, which increase the CO2 concentration around Rubisco, were all based on active transport of CO2, H+CO3 -, or H++ across membranes. It now appears, from recent extensions of earlier work, that there is a C4-like photosynthetic carbon metabolism in certain diatoms. H+owever, more work is needed to determine the extent to which diatoms have photosynthesis analogous to that of single-cell C4 higher plants. The relevance of this work to producing C4 rice probably comes more from concepts than from the direct introduction of diatom genes in rice. One such concept is the possibility that C4-like photosynthesis in diatoms involves no carbonic anhydrases (CAs), and so needs less Zn. H+owever, this requires H+CO3 - entry, so decreased Zn costs of growth may be less readily achieved in rice unless phosphoenolpyruvate carboxykinase (using CO2) replaces phosphoenolpyruvate carboxylase (using H+CO3 -) as the C4 carboxylase.
© Oxford University Press 2005. All rights reserved. This chapter discusses respiratory processes in phytoplankton to demonstrate the range of respiratory processes found in phytoplankton, describe the functions of these individual pathways, and explore their interactions. Phytoplankton organisms have core respiratory processes common to most planktonic organisms; these reactions occur in the dark and, to varying extents, in the light. These organisms also experience oxygen uptake and carbon dioxide production reactions related to their photosynthetic apparatus. Two of these, the Mehler-peroxidase reaction and the oxidase function of ribulose biphosphate carboxylase-oxygenase (RUBISCO), are light dependent; a third, chlororespiration, occurs mainly in the dark.
Raven, JA, Brown, K, Mackay, M, Beardall, J, Giordano, M, Granum, E, Leegood, RC, Kilminster, K & Walker, DI 2005, 'Iron, nitrogen, phosphorus and zinc cycling and consequences for primary productivity in the oceans' in Micro-Organisms and Earth Systems - Advances in Geomicrobiology: Published for the Society for General Microbiology, pp. 247-272.View/Download from: Publisher's site
© Society for General Microbiology 2005. INTRODUCTION: Primary productivity in the ocean amounts to the net assimilation of CO2 equivalent to about 50 Pg (petagram, i.e. 1015g) C year-1, while on land this is approximately 60 Pg C year-1(Field et al., 1998). Almost all of this primary productivity involves photosynthesis, and in the ocean it occurs only in the top few hundred metres, even in waters with the smallest light attenuation (Falkowski & Raven, 1997). About 1 Pg C of marine primary productivity involves benthic organisms, i.e. those growing on the substratum (Field et al., 1998), in the very small fraction of the ocean which is close enough to the surface to permit adequate photosynthetically active radiation (PAR) to allow photolithotrophic growth. This depth at which photosynthetic growth is just possible varies in time and space, and defines the bottom of the euphotic zone (Falkowski & Raven, 1997). The remaining 49 Pg C is assimilated by phytoplankton in the water column (Field et al., 1998). This chapter will concentrate on the planktonic realm, while acknowledging the importance of marine benthic primary producers and their interactions with micro-organisms (e.g. Dudley et al., 2001; Raven et al., 2002; Raven & Taylor, 2003; Cooke et al., 2004; Walker et al., 2004). The global net primary productivity of the oceans is less than that on land, despite about 70 % of the Earth being covered in ocean and primary productivity over considerable areas of land being limited by water supply.
Raven, JA & Edwards, D 2004, 'Physiological evolution of lower embryophytes: Adaptations to the terrestrial environment' in The Evolution of Plant Physiology, pp. 17-41.View/Download from: Publisher's site
This chapter examines the differences in physiology among embryophytes and their algal ancestors, with particular emphasis on their water relations. The embryophytes have very significant variations in water relations and the chapter considers their evolution within the embryophytes as well as the evolution of embryophyte water relations from those of their algal ancestors. The chapter also examines the relationship of the likely evolution of embryophyte water relations to cladistic analyses of embryophyte phylogeny and to the fossil record. The physiological changes that occurred in the evolution from algal ancestors to the different grades of organization of embryophytes has been determined from the physiology of extant plants in relation to their phylogeny as determined by cladistic analysis and from the order in which anatomical features appeared in the fossil record. The fossil record of embryophytes also reveals certain characteristics of organisms that are not found today. The fossil record is not helpful in providing some information such as desiccation tolerance or intolerance, except by applying an empirical correlation from extant plants that no embryophyte more than 1 meter in height is desiccation tolerant in the vegetative phase. Overall, lines of evidence indicate that the earliest embryophytes were desiccation tolerant and poikilohydric. © 2004 Elsevier Ltd. All rights reserved.
Raven, JA & Skene, KR 2003, 'Chemistry of the early oceans: The environment of early life' in Evolution on Planet Earth: The Impact of the Physical Environment, pp. 55-64.View/Download from: Publisher's site
This chapter discusses chemistry of the ocean in relation to the origin and early evolution of life. The chapter emphasizes on how the early ocean could supply the energy and materials needed for extant life and also of putative ancestral organisms and prebiotic components. The chapter begins with an outline of the likely chemical composition of the Hadean Ocean, including changes to ocean chemistry because of interactions with the earth's crust and with the atmosphere. Furthermore, the chapter also considers the ways in which the Hadean Ocean could have supplied the materials and the energy needed for the origin and early evolution of life. This view focuses on ocean and atmosphere interactions as most significant in providing the energy for early life to the ocean. Later the direct use of light energy by organisms at the ocean surface became the major energy transforming reaction, providing energy for almost all living organisms. The chemical elements that were used by the earliest organisms were determined by their availability to early organisms as well as by their physicochemical appropriateness for particular biological functions. Modification of ocean chemistry by the activities of living organisms-for example, the accumulation of photosynthetically produced oxygen-changed the availability of several biologically essential elements. The chapter concludes with a discussion on how early life could have modified the chemistry of the ocean, and how these changes could have fed back to the evolution of the early organisms. © 2003 Elsevier Ltd. All rights reserved.
O'Malley-James, JT, Greaves, JS, Raven, JA & Cockell, CS 2013, 'Swansong biospheres: The biosignatures of inhabited earth-like planets nearing the end of their habitable lifetimes', Proceedings of the International Astronomical Union, IAUS 299: Exploring the formation and evolution of planetary systems, pp. 378-379.View/Download from: UTS OPUS or Publisher's site
The biosignatures of life on Earth are not fixed, but change with time as environmental conditions change and life living within those environments adapts to the new conditions. A latitude-based climate model, incorporating orbital parameter variations, was used to simulate conditions on the far-future Earth as the Sun enters the late main sequence. Over time, conditions increasingly favour a unicellular microbial biosphere, which can persist for a maximum of 2.8 Gyr from present. The biosignature changes associated with the likely biosphere changes are evaluated using a biosphere-atmosphere gas exchange model and their detectability is discussed. As future Earth-like exoplanet discoveries could be habitable planets nearing the end of their habitable lifetimes, this helps inform the search for the signatures of life beyond Earth Copyright © 2013, International Astronomical Union.
Bryce, JH, Scott, MB, McCafferty, KA, Johnston, AM, Raven, JA, Thornton, JM, Morris, PC & Footitt, S 2010, 'Mobilisation of energy reserves in barley grains during imbibition of water', DISTILLED SPIRITS: NEW HORIZONS, pp. 39-47.
Raven, JA 1970, 'Contributions of anoxygenic and oxygenic phototrophy and chemolithotrophy to carbon and oxygen fluxes in aquatic environments', AQUATIC MICROBIAL ECOLOGY, 8th International Workshop of the Group-for-Aquatic-Primary-Productivity, INTER-RESEARCH, Eilat, ISRAEL, pp. 177-192.View/Download from: Publisher's site
Carfrae, JA, Sheppard, LJ, Raven, JA, Leith, ID & Crossley, A 2005, 'Potassium and phosphorus additions modify the response of Sphagnum capillifolium growing on a Scottish ombrotrophic bog to enhanced nitrogen deposition', APPLIED GEOCHEMISTRY, 7th International Conference on Acid Deposition, PERGAMON-ELSEVIER SCIENCE LTD, Prague, CZECH REPUBLIC, pp. 1111-1121.View/Download from: Publisher's site
Permineralized xylem strands in an otherwise coalified pseudomonopodially branching axis from the Lower Devonian of Röragen, Norway, allow the description of the architecture of the presumed tracheids using scanning electron microscopy, and a discussion on the roles of the various types of pitting in the functioning of the water-conducting cells. Tracheid construction differs in the main axis and lateral branch. The former has G-type tracheids in which close-set annular secondary thickenings are connected by a further microperforated secondary layer lining the imperforate presumed primary wall. Tracheids in the lateral branch possess bordered pits that may be circular, elliptical or scalariform, with rare examples of reticulate pitting. The secondary wall structures of the tracheids are discussed in relation to their major roles, namely conduction, mechanical strength and safety (i.e. prevention of implosion and embolism) and to different needs in different parts of the plant. It is suggested that in the main axis, tracheids are adapted for longitudinal transport of water with their abundant (presumed) lignification providing mechanical strength and resistance to embolism. In the lateral branch, by contrast, they are apparently adapted for rapid lateral transport at the expense of their structural and safety roles. © 2006 The Linnean Society of London.
Raven, JA, Ball, LA, Beardall, J, Giordano, M & Maberly, SC 2004, 'Algae lacking carbon-concentrating mechanisms', CANADIAN JOURNAL OF BOTANY-REVUE CANADIENNE DE BOTANIQUE, 5th International Symposium on Inorganic Carbon Utilization by Aquatic Photosynthetic Organisms, CANADIAN SCIENCE PUBLISHING, NRC RESEARCH PRESS, St Sauveur, CANADA, pp. 879-890.View/Download from: Publisher's site
Granum, E, Raven, JA & Leegood, RC 2004, 'How do marine diatoms fix 10 billion tonnes of inorganic carbon per year?', CANADIAN JOURNAL OF BOTANY-REVUE CANADIENNE DE BOTANIQUE, 5th International Symposium on Inorganic Carbon Utilization by Aquatic Photosynthetic Organisms, CANADIAN SCIENCE PUBLISHING, NRC RESEARCH PRESS, St Sauveur, CANADA, pp. 898-908.View/Download from: Publisher's site
Beardall, J, Roberts, S & Raven, JA 2004, 'Regulation of inorganic carbon acquisition by phosphorus limitation in the green alga Chlorella emersonii', CANADIAN JOURNAL OF BOTANY-REVUE CANADIENNE DE BOTANIQUE, 5th International Symposium on Inorganic Carbon Utilization by Aquatic Photosynthetic Organisms, NATL RESEARCH COUNCIL CANADA, St Sauveur, CANADA, pp. 859-864.View/Download from: Publisher's site
Raven, JA 2004, 'Symbiosis, size and celerity', Symbiosis, pp. 281-291.
Description of the way in which metabolic and growth rates scale with the size of organisms, and the search for mechanisms which determine these relationships, is an important aspect of the growing field of macroecology. Symbiosis is not specifically addressed in most of the published investigations of these allometric relationships, despite the near ubiquity of symbioses and the possibility that studies of allometry can give insights into nature of symbioses and vice versa. Using chemoorganotrophic organisms in symbiosis with microscopic photobionts as an example, the literature was analyzed for data sets that could be used in allometric analyses. Few such data sets were found. It is argued that further such data sets, perhaps obtained as part of research programmes whose primary aim is not to investigate allometry, would be helpful in determining if symbioses follow similar allometric relations to the (putatively) non-symbiotic organism for which data are available, and would illuminate discussions on the applicability of optimality principle to symbioses.
Douglas, AE & Raven, JA 2003, 'Genomes at the interface between bacteria and organelles.', Philosophical transactions of the Royal Society of London. Series B, Biological sciences, pp. 5-17.View/Download from: Publisher's site
The topic of the transition of the genome of a free-living bacterial organism to that of an organelle is addressed by considering three cases. Two of these are relatively clear-cut as involving respectively organisms (cyanobacteria) and organelles (plastids). Cyanobacteria are usually free-living but some are involved in symbioses with a range of eukaryotes in which the cyanobacterial partner contributes photosynthesis, nitrogen fixation, or both of these. In several of these symbioses the cyanobacterium is vertically transmitted, and in a few instances, sufficient unsuccessful attempts have been made to culture the cyanobiont independently for the association to be considered obligate for the cyanobacterium. Plastids clearly had a cyanobacterial ancestor but cannot grow independently of the host eukaryote. Plastid genomes have at most 15% of the number of genes encoded by the cyanobacterium with the smallest number of genes; more genes than are retained in the plastid genome have been transferred to the eukaryote nuclear genome, while the rest of the cyanobacterial genes have been lost. Even the most cyanobacteria-like plastids, for example the "cyanelles" of glaucocystophyte algae, are functionally and genetically very similar to other plastids and give little help in indicating intermediates in the evolution of plastids. The third case considered is the vertically transmitted intracellular bacterial symbionts of insects where the symbiosis is usually obligate for both partners. The number of genes encoded by the genomes of these obligate symbionts is intermediate between that of organelles and that of free-living bacteria, and the genomes of the insect symbionts also show rapid rates of sequence evolution and AT (adenine, thymine) bias. Genetically and functionally, these insect symbionts show considerable similarity to organelles.
Allen, JF, Raven, JA, Douglas, AE, Cavalier-Smith, T, Blankenship, RE, Lopez-Juez, E, Bauer, CE, Russell, MJ, Martin, W, Nisbet, E, Doolittle, WF, Embley, TM, Whatley, FR & Tovar, J 2003, 'General discussion', PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY OF LONDON SERIES B-BIOLOGICAL SCIENCES, ROYAL SOC LONDON, pp. 217-222.View/Download from: Publisher's site
Allen, JF & Raven, JA 2003, 'Chloroplast and mitochondria: Functional genomics and evolution: Introduction', Philosophical Transactions of the Royal Society B: Biological Sciences, pp. 3-4.View/Download from: Publisher's site
Raven, JA, Johnston, AM, Kubler, JE, Korb, R, McInroy, SG, Handley, LL, Scrimgeour, CM, Walker, DI, Beardall, J, Vanderklift, M, Fredriksen, S & Dunton, KH 2002, 'Mechanistic interpretation of carbon isotope discrimination by marine macroalgae and seagrasses', FUNCTIONAL PLANT BIOLOGY, CSIRO PUBLISHING, pp. 355-378.View/Download from: Publisher's site
Andrews, M, Raven, JA & Sprent, JI 2000, 'Environmental effects on dry matter partitioning between shoot and root of crop plants: relations with growth and shoot protein concentration', ANNALS OF APPLIED BIOLOGY, Meeting of the Association-of-Applied-Biologists, WILEY, ABERYSTWYTH, WALES, pp. 57-68.View/Download from: Publisher's site
Beardall, J, Johnston, A & Raven, J 1998, 'Environmental regulation of CO2-concentrating mechanisms in microalgae', CANADIAN JOURNAL OF BOTANY-REVUE CANADIENNE DE BOTANIQUE, pp. 1010-1017.
Kubler, JE & Raven, JA 1970, 'Inorganic carbon acquisition by red seaweeds grown under dynamic light regimes', HYDROBIOLOGIA, 15th International Seaweed Symposium, KLUWER ACADEMIC PUBL, VALDIVIA, CHILE, pp. 401-406.
Brenchley, JL, Raven, JA & Johnston, AM 1996, 'A comparison of reproductive allocation and reproductive effort between semelparous and iteroparous fucoids (Fucales, Phaeophyta)', Hydrobiologia, pp. 185-190.View/Download from: Publisher's site
Reproductive allocation, the proportion of total dry weight allocated to receptacle tissue and reproductive effort, the proportion of reproductive carbon requirement contributed by receptacle photosynthesis, were measured in two fucoid algal species Fucus serratus and Himanthalia elongata at sites in NE Scotland. Reproductive development takes over ten months in H. elongata, a semelparous (single reproductive event) species, and reproductive allocation at receptacle maturity is over 98%. Following gamete release, the whole thallus dies. In contrast, reproductive development in F. serratus takes four months. Fucus serratus is iteroparous (capable of multiple reproductive events), reproductive allocation is 38.6% for the first reproductive event and 50.5% for the following year's event. In Fucus serratus, the receptacles appear to make a major contribution to their own carbon requirements after the first mouth of reproductive development. The receptacles of Himanthalia elongata contribute only a small proportion of the receptacle carbon requirements in the first four months of reproductive development, after which the contribution made through receptacle photosynthesis increases.