Algorithm for analysis of OJDIP fluorescence induction curves in terms of photo- and electrochemical events in photosystems of plant cells: derivation and application

The algorithm for simulation of the OJDIP fluorescence induction curve in chloroplasts under variable conditions is presented. It is derived from analyzes of chlorophyll a fluorescence kinetics upon excitation with single- (STF), twin- (TTF) and repetitive STF excitations, and from the rate equations that describe the sequence of transfer steps associated with the reduction of the primary quinone acceptor Q(A) and the release of photochemical fluorescence quenching of photosystem II (PSII) in multi-turnover excitation (MTF). The fluorescence induction algorithm (FIA) considers a photochemical O-J-D, a photo-electrochemical J-I and an I-P component (phase) which probably is associated with a photo-electric interaction between PSI and PSII. The photochemical phase incorporates the kinetics associated with the double reduction of the acceptor pair [PheQ(A)] in Q(B)-nonreducing reaction centers (RCs) and the associated doubling of the variable fluorescence, in agreement with the three-state trapping model (TSTM) of PSII. Application of and results with the algorithm are illustrated for MTF-induced OJDIP curves, measured in dark-adapted, in STF pre-excited and in DCMU inhibited thylakoids.