Elevated Temperatures Inhibit Ferredoxin-Dependent Cyclic Electron Flow around Photosystem I

Elevated Temperatures Inhibit Ferredoxin-Dependent Cyclic Electron Flow around Photosystem I In experiments with barley (Hordeum vulgare L.) leaves, absorbance changes at 830 nm induced by far-red light were measured as indicator of redox conversions of primary electron donor (P700) of photosystem I (PSI). Using this method, the action of elevated temperature (45°C, 5 min) on PSI-driven electron transport through alternative pathways was examined. Thermally induced inactivation was found to transform nonmonotonic photooxidation of P700, induced by far-red light in untreated leaves, into a fast and monotonic process completed within 1-s illumination. The short-term heating of leaves fully eliminated the fast component in the kinetics of P700+ dark reduction, related to operation of ferredoxin-dependent cyclic electron transport around PSI. At the same time, thermoinactivation substantially accelerated the slow and middle components of dark P700+ reduction, i.e., the components determined by arrival of electrons to PSI from reductants located in the chloroplast stroma. The latter effect was also observed after heating of leaves pretreated with antimycin A or methyl viologen; both agents are known to inhibit the ferredoxin-dependent electron transport. It is concluded that the heat treatment of leaves inhibits the ferredoxin-dependent pathway of electron transport around PSI and activates electron transport through alternative routes providing reducing equivalents to PSI from stromal reductants. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Russian Journal of Plant Physiology Springer Journals

Elevated Temperatures Inhibit Ferredoxin-Dependent Cyclic Electron Flow around Photosystem I

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Copyright © 2005 by MAIK "Nauka/Interperiodica"
Life Sciences; Plant Sciences; Plant Physiology
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