A simple model relating photoinhibitory fluorescence quenching in chloroplasts to a population of altered Photosystem II reaction centers |
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Authors: | Christoph Giersch G. Heinrich Krause |
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Affiliation: | (1) Botanical Institute, Technical University Darmstadt, Schnittspahnstr. 3-5, D-6100 Darmstadt;(2) Institute for Biochemistry of Plants, Heinrich Heine University Düsseldorf, Universitätsstr. 1, D-4000 Düsseldorf 1, Germany |
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Abstract: | A model is presented describing the relationship between chlorophyll fluorescence quenching and photoinhibition of Photosystem (PS) II-dependent electron transport in chloroplasts. The model is based on the hypothesis that excess light creates a population of inhibited PS II units in the thylakoids. Those units are supposed to posses photochemically inactive reaction centers which convert excitation energy to heat and thereby quench variable fluorescence. If predominant photoinhibition of PS II and cooperativity in energy transfer between inhibited and active units are presumed, a quasi-linear correlation between PS II activity and the ratio of variable to maximum fluorescence, FVFM, is obtained. However, the simulation does not result in an inherent linearity of the relationship between quantum yield of PS II and FVFM ratio. The model is used to fit experimental data on photoinhibited isolated chloroplasts. Results are discussed in view of current hypotheses of photoinhibition.Abbreviations FM maximum total fluorescence - F0 initial fluorescence - FV maximum variable fluorescence - PS Photosystem - QA, QB primary and secondary electron acceptors of Photosystem II |
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Keywords: | chlorophyll fluorescence electron transport photochemical reaction (in Photosystem II) photoinhibition of photosynthesis |
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