A novel P700 redox kinetics probe for rapid,non‐intrusive and whole‐tissue determination of photosystem II functionality,and the stoichiometry of the two photosystems in vivo |
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| Authors: | Simon A Dwyer Da‐Yong Fan Murray R Badger Susanne von Caemmerer Wah Soon Chow |
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| Institution: | 1. Division of Plant Science, Research School of Biology, College of Medicine, Biology and Environment, The Australian National University, , Canberra, Australia;2. State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, The Chinese Academy of Sciences, , Beijing, 100093 China |
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| Abstract: | We sought a rapid, non‐intrusive, whole‐tissue measure of the functional photosystem II (PS II) content in leaves. Summation of electrons, delivered by a single‐turnover flash to P700+ (oxidized PS I primary donor) in continuous background far‐red light, gave a parameter S in absorbance units after taking into account an experimentally determined basal electron flux that affects P700 redox kinetics. S was linearly correlated with the functional PS II content measured by the O2 yield per single‐turnover repetitive flash in Arabidopsis thaliana expressing an antisense construct to the PsbO (manganese‐stabilizing protein in PS II) proteins of PS II (PsbO mutants). The ratio of S to zmax (total PS I content in absorbance units) was comparable to the PS II/PS I reaction‐center ratio in wild‐type A. thaliana and in control Spinacea oleracea. Both S and S/zmax decreased in photoinhibited spinach leaf discs. The whole‐tissue functional PS II content and the PS II/photosystem I (PS I) ratio can be non‐intrusively monitored by S and S/zmax, respectively, using a quick P700 absorbance protocol compatible with modern P700 instruments. |
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