A simple routine for quantitative analysis of light and dark kinetics of photochemical and non-photochemical quenching of chlorophyll fluorescence in intact leaves

Paper describes principles and application of a novel routine that enables the quantitative analysis of the photochemical O-J phase of the variable fluorescence F (v) associated with the reversible photo-reduction of the secondary electron acceptor Q(A) of photosystem II (PSII) in algae and intact leaves. The kinetic parameters that determine the variable fluorescence F (PP)(t) associated with the release of photochemical quenching are estimated from 10 A mu s time-resolved light-on and light-off responses of F (v) induced by two subsequent light pulses of 0.25 (default) and 1000 ms duration, respectively. Application of these pulses allows estimations of (i) the actual value of the rate constants k (L) and k (AB) of the light excitation (photoreduction of Q(A)) and of the dark re-oxidation of photoreduced Q(A) (), respectively, (ii) the actual maximal normalized variable fluorescence [nF (v)] associated with 100 % photoreduction of Q(A) of open RCs, and (iii) the actual size beta of RCs in which the re-oxidation of is largely suppressed (Q(B)-nonreducing RC with k (AB) 0). The rate constants of the dark reversion of Fv associated with the release of photo-electrochemical quenching F (PE) and photo-electric stimulation F (CET) in the successive J-I and I-P parts of the thermal phase are in the range of (100 ms)(-1) and (1 s)(-1), respectively. The kinetics of fluorescence changes during and after the I-P phase are given special attention in relation to the hypothesis on the involvement of a Delta A mu (H+)-dependent effect during this phase and thereafter. Paper closes with author's personal view on the demands that should be fulfilled for chlorophyll fluorescence methods being a correct and unchallenged signature of photosynthesis in algae and plants.