A Hypothetical Model for the Structure and Function of the Photosystem II Reaction Center
Chlorophyll fluorescence has extensively been used to investigate the function of Photosystem II reaction centers (PSII RC) of higher plants (see Ref. 1.). The assignment of variable chlorophyll fluorescence to the redox state of PSII RC2 has been of prime importance for these investigations. However, the interpretation of fluorescence signals is still encumbered by two major problems: the discrepancy between the measured and predicted Fm/Fo ratios3 and the presence under physiological conditions4 of the “energy-dependent” quenching5 (qg) in addition to photochemical quenching2 (qg). To account for these phenomena, the existence of a radiationless deactivation pathway in “closed” reaction centers was postulated3. It is considered4 to be of non-photochemical nature and to depend on ultrastructural changes of the thylakoid membrane.
KeywordsReaction Center Chlorophyll Fluorescence Fluorescence Yield PSII Reaction Center Primary Charge Separation
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