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Oxygen reduction in the Mehler reaction is insufficient to protect photosystems I and II of leaves against photoinactivation
Author(s) -
Wiese Christian,
Shi Lanbo,
Heber Ulrich
Publication year - 1998
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1034/j.1399-3054.1998.1020312.x
Subject(s) - photorespiration , photosystem ii , chemistry , p680 , chlorophyll fluorescence , photochemistry , electron transport chain , photosynthesis , photoinhibition , photosystem , spinacia , spinach , photosystem i , singlet oxygen , violaxanthin , oxygen , biophysics , biochemistry , biology , zeaxanthin , lutein , chloroplast , carotenoid , organic chemistry , gene
The relative roles of assimilatory and photorespiratory electron flows on one side and of the Mehler‐peroxidase pathway on the other side in sustaining electron transport and providing protection against photoinhibition were investigated in leaves of spinach ( Spinacia oleracea L.) and sunflower ( Helianthus annuus L.). After inhibiting photosynthesis and photorespiration of intact leaves by either HCN or glycolaldehyde, light‐dependent linear electron transport was decreased by more than 90% at a photon flux density of 800 µmol m −2 s −1 . Remaining electron transport exhibited characteristics of the Mehler reaction. Nonphotochemical quenching of chlorophyll fluorescence increased after inhibition of CO 2 assimilation and photorespiration indicating effective dissipation of excess excitation energy. Nevertheless, appreciable photoinactivation was observed under these conditions not only of photosystem II but also of photosystem I. This damage was oxygen‐dependent. It was much reduced or absent when the oxygen concentration of the atmosphere was reduced from 21 to 1%.