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 Fv associated with the reversible photo-reduction of the secondary electron acceptor QA of photosystem II (PSII) in algae and intact leaves. The kinetic parameters that determine the variable fluorescence FPP(t) associated with the release of photochemical quenching are estimated from 10 µs time-resolved light-on and light-off responses of Fv 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 kL and kAB of the light excitation (photoreduction of QA) and of the dark re-oxidation of photoreduced QA (QA-\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\text{Q}}_{\text{A}}^{ - }$$\end{document}), respectively, (ii) the actual maximal normalized variable fluorescence [nFv] associated with 100 % photoreduction of QA of open RCs, and (iii) the actual size β of RCs in which the re-oxidation of QA-\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\text{Q}}_{\text{A}}^{ - }$$\end{document} is largely suppressed (QB-nonreducing RC with kAB ~ 0). The rate constants of the dark reversion of Fv associated with the release of photo-electrochemical quenching FPE and photo-electric stimulation FCET 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 ΔµH+-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.