Non-photochemical energy dissipation in photosystem II: Theoretical modelling of the energy-dependent quenching of chlorophyll fluorescence emission from intact plant leaves
Journal of Photochemistry and Photobiology B Biology 19(2): 97-104
Experimentally, there is a hyperbolic relationship between the maximal and minimal levels of in vivo chlorophyll fluorescence from photosystem II (F-m-(t) and F-o-(t) respectively) during dark-induced relaxation of the "energy dependent quenching" mechanism (q-E). In this paper, a theoretical analysis of q-E is presented which describes this behaviour. The dissipative process leading to q-E is assumed to quench excitation energy in the photosystem II (PSII) pigment antenna and is characterized by a rate constant k-E whose value is modulated by the pH gradient. Introducing this rate constant into the theoretical expression of F-o presented in a previous paper (M. Havaux, R. J. Strasser and H. Greppin, Photosynth. Res., 27 (1991) 41-55), an equation relating F-m-(t) to F-o(t) by a first-order hyperbola is derived, which allows the macroscopic changes in the F-m-(t) amplitude to be predicted at various levels of q-E. A very good agreement was obtained between predicted and experimental data. Simple fluorescence parameters are also derived which provide relative estimates of the value of k-E and allow (assuming no energy exchanges between PSII units) the determination of the probability p-E for energy dissipation via the q-E mechanism. Some experimental applications for the rate constant k-E are given.