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RESEARCH PRODUCT

Picosecond Time Resolved Analysis of the Fast and Slow Reversible Non-Photochemical Chlorophyll Fluorescence Quenching

subject

description

Photosystem II, which is a potential target of adverse effects of supersaturating light, is strongly dependent on a mechanism, which allows to switch over between efficient photochemical energy conversion at limiting light intensity and efficient photothermal energy conversion under strong light. The mechanisms for the thermal dissipation of light absorbed in excess are reflected by the socalled non-photochemical quenching of chlorophyll fluorescence (NPQ). Under excessive illumination two major components contribute to the overall NPQ which can be distinguished by their different kinetics of dark relaxation. The fast reversible component is supposed to be linked to the light-induced formation of a proton gradient across the thylakoid membrane and is thus called “high-energy-state quenching“ (qE). A slow reversible component of NPQ has been termed “photoinhibitory“ quenching (qI) because of its occurrence during photoinhibition. The kinetics of its relaxation in the dark implies that it is independent of the ΔpH.