Mathematical model of prompt and delayed chlorophyll fluorescence induction kinetics

Parallel investigation of the induction kinetics of prompt (PF) and delayed (DF) chlorophyll (Chi) fluorescence in pea and barley leaves showed the existence of three kinetic components of DF, with maxima at about 33 ms, 100 ms and 5 s. The maxima of DF kinetics coincided with the inflection points of the corresponding phases of PF. The analysis of the effects of some photosystem 2 (PS2) modificators indicated that the experimentally measured two-phase kinetics, both of PF and DF in the ms time range, could be the result of transitions between the redox states of the PS2 quinone acceptors, Q(A) and Q(B). A mathematical model of the kinetics of redox reactions between the quinone acceptors and thylakoid membrane energization, associated with emission of DF and PF, was developed. The numeric analysis of the model shows that the first DF phase as well as the F-0-F-i fluorescent phase are a result of the photoinduced transitions Q(A)Q(B) --> Q(A)Q(B)(-) and Q(A)Q(B)(-)--> Q(A)W(B)(=). The Second maximum of DF as well as the F-i-F-p phase of fluorescence correlate with the Q(A)Q(B)(=) --> Q(A)(-)Q(B)(=) transition.