Chris combines his creativity and technology expertise with his scientific curiosity to build new tools for scientific research.
His speciality is measuring the photosynthetic efficiency of plants and microalgae in dynamic outdoor environments. Unlike the typical laboratory environment, the world in which plants and algae evolved was one of constant change, with rapid fluctuations in light, temperature, and in some cases carbon dioxide and oxygen. If we intend to harness the power of photosynthesis to replace petroleum products, then it is essential that we understand how the fluctuations of the real-world environment will impact the efficiency of our photobioreactors.
Chris studied biochemistry and genetics at the University of Minnesota for his bachelor's of science degree and then earned his PhD from the department of Plant Biology at Michigan State University.
- Co-founder of Phenometrics Inc.
Tietz, S, Hall, CC, Cruz, JA & Kramer, DM 2017, 'NPQ(T) : a chlorophyll fluorescence parameter for rapid estimation and imaging of non-photochemical quenching of excitons in photosystem-II-associated antenna complexes.', Plant, cell & environment, vol. 40, no. 8, pp. 1243-1255.View/Download from: UTS OPUS or Publisher's site
In photosynthesis, light energy is absorbed by light-harvesting complexes and used to drive photochemistry. However, a fraction of absorbed light is lost to non-photochemical quenching (NPQ) that reflects several important photosynthetic processes to dissipate excess energy. Currently, estimates of NPQ and its individual components (qE , qI , qZ and qT ) are measured from pulse-amplitude-modulation (PAM) measurements of chlorophyll fluorescence yield and require measurements of the maximal yield of fluorescence in fully dark-adapted material (Fm ), when NPQ is assumed to be negligible. Unfortunately, this approach requires extensive dark acclimation, often precluding widespread or high-throughput use, particularly under field conditions or in imaging applications, while introducing artefacts when Fm is measured in the presence of residual photodamaged centres. To address these limitations, we derived and characterized a new set of parameters, NPQ(T) , and its components that can be (1) measured in a few seconds, allowing for high-throughput and field applications; (2) does not require full relaxation of quenching processes and thus can be applied to photoinhibited materials; (3) can distinguish between NPQ and chloroplast movements; and (4) can be used to image NPQ in plants with large leaf movements. We discuss the applications benefits and caveats of both approaches.
Cruz, JA, Savage, LJ, Zegarac, R, Hall, CC, Satoh-Cruz, M, Davis, GA, Kovac, WK, Chen, J & Kramer, DM 2016, 'Dynamic Environmental Photosynthetic Imaging Reveals Emergent Phenotypes', CELL SYSTEMS, vol. 2, no. 6, pp. 365-377.View/Download from: Publisher's site
Lucker, BF, Hall, CC, Zegarac, R & Kramer, DM 2014, 'The environmental photobioreactor (ePBR): An algal culturing platform for simulating dynamic natural environments', ALGAL RESEARCH-BIOMASS BIOFUELS AND BIOPRODUCTS, vol. 6, pp. 242-249.View/Download from: Publisher's site
Kirchhoff, H, Hall, C, Wood, M, Herbstová, M, Tsabari, O, Nevo, R, Charuvi, D, Shimoni, E & Reich, Z 2011, 'Dynamic control of protein diffusion within the granal thylakoid lumen', Proceedings of the National Academy of Sciences of the United States of America, vol. 108, no. 50, pp. 20248-20253.View/Download from: Publisher's site
The machinery that conducts the light-driven reactions of oxygenic photosynthesis is hosted within specialized paired membranes called thylakoids. In higher plants, the thylakoids are segregated into two morphological and functional domains called grana and stroma lamellae. A large fraction of the luminal volume of the granal thylakoids is occupied by the oxygen-evolving complex of photosystem II. Electron microscopy data we obtained on dark- and light-adapted Arabidopsis thylakoids indicate that the granal thylakoid lumen significantly expands in the light. Models generated for the organization of the oxygen-evolving complex within the granal lumen predict that the light-induced expansion greatly alleviates restrictions imposed on protein diffusion in this compartment in the dark. Experiments monitoring the redox kinetics of the luminal electron carrier plastocyanin support this prediction. The impact of the increase in protein mobility within the granal luminal compartment in the light on photosynthetic electron transport rates and processes associated with the repair of photodamaged photosystem II complexes is discussed.
Hall, CC, Cruz, J, Wood, M, Zegarac, R, DeMars, D, Carpenter, J, Kanazawa, A & Kramer, D 2013, 'Photosynthetic measurements with the idea spec: An integrated diode emitter array spectrophotometer/fluorometer' in Advanced Topics in Science and Technology in China, pp. 184-188.View/Download from: Publisher's site
© Zhejiang University Press, Hangzhou and Springer-Verlag Berlin Heidelberg 2013. In vivo spectrophotometry, a non-invasive, nondestructive technique that relies on the leaf's endogenous chromophores, has become an essential tool for understanding the photosynthetic response of plants to environmental stresses. Based on the pulsed-light spectrophotometer approach, and capitalizing on recent advances in optics and light emitting diode (LED) technology, we have developed an in vivo spectrophotometer capable of measuring absorbance changes of less than 3 × 10 −5 absorption units and microsecond time resolution. The instrument can also simultaneously measure chlorophyll (or other) fluorescence signals with background or saturating actinic light, e.g. PAM fluorometry or induction curves, to give measurements of antenna and photosystem II efficiencies. We use a solid-state light source containing multiple LEDs for both measuring and actinic stimulation and direct the light to the leaf through non-focusing optics, allowing near-simultaneous multi-wavelength measurements useful for signal deconvolution.