title: The relationship between non-photochemical quenching of chlorophyll fluorescence and the rate of photosystem 2 photochemistry in leaves.
abstract: It has been suggested previously that non-photochemical quenching of chlorophyll fluorescence is associated with a decrease in the rate of photosystem 2 (PS 2) photochemistry. In this study analyses of fluorescence yield changes, induced by flashes in leaves exhibiting different amounts of non-photochemical quenching of fluorescence, are made to determine the effect of non-photochemical excitation energy quenching processes on the rate of PS 2 photochemistry. It is demonstrated that both the high-energy state and the more slowly relaxing components of non-photochemical quenching reduce the rate of PS 2 photochemistry. Flash dosage response curves for fluorescence yield show that non-photochemical quenching processes effectively decrease the relative effective absorption cross-section for PS 2 photochemistry. It is suggested that non-photochemical quenching processes exert an effect on the rate of PS 2 photochemistry by increasing the dissipation of excitation energy by non-radiative processes in the pigment matrices of PS 2, which consequently results in a decrease in the efficiency of delivery of excitation energy for PS 2 photochemistry.
authors.affiliation: Department of Biology, University of Essex, CO4 3SQ, Colchester, Essex, UK.
authors.forename: B
authors.initials: B
authors.lastname: Genty
authors.forename: J
authors.initials: J
authors.lastname: Harbinson
authors.forename: J M
authors.initials: JM
authors.lastname: Briantais
authors.forename: N R
authors.initials: NR
authors.lastname: Baker