Tracking photosynthetic electron transfers under environmental stress

Prof. (Fred) W.S. Chow (see ISI Highly Cited)
Prof Alex Hope (Flinders University)

The two photosystems in the chloroplast work in series to deliver electrons from the substrate water to NADP+ in two light-driven uphill steps, conserving the light energy as chemical energy in NADPH and ATP.

In addition to this linear electron flow, there is a cyclic electron pathway mediated by ferredoxin around Photosystem I, another Photosystem I cyclic pathway involving NADPH, a Q cycle around the cytochrome bf complex, as well as electron donation from stromal reductants.  A challenge is to quantify these separate electron fluxes, all except one of which pass through P700, the primary electron donor in Photosystem I, and to do so in leaves without having to isolate the chloroplasts.  How do these fluxes vary under different environmental conditions?  What roles do the electron fluxes play in the protection of the photosynthetic apparatus under environmental stress, such as high light and/or drought?  The overall goal is to decipher the various electron fluxes in situ, with leaves functioning in defined environmental conditions.

Techniques:    
kinetic in vivo optical spectrophotometry; chlorophyll fluorescence techniques; biochemical techniques; oxygen measurements.

References:
Chow WS and Hope AB (2004) Electron fluxes through Photosystem I in cucumber leaf discs probed by far-red light. Photosynthesis Research 81: 77-89

Chow WS and Hope AB (2004) Kinetics of reactions around the cytochrome bf complex studies in intact leaf disks. Photosynthesis Research 81: 153-163

Fan, D-Y, Nie Q, Hope AB, Hillier W, Pogson BJ and Chow WS (2007) Quantification of cyclic electron flow around Photosystem I in spinach leaves during photosynthetic induction. Photosynthesis Research. 94: 347-357

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