Quantitative analysis of the experimental O-J-I-P chlorophyll fluorescence induction kinetics. Apparent activation energy and origin of each kinetic step

Fluorescence induction has been studied for a long time, but there are still questions concerning what the O-J-I-P kinetic steps represent. Most studies agree that the O-J rise is related to photosystem II primary acceptor (Q(A)) reduction, but several contradictory theories exist for the J-I and I-P rises. One problem with fluorescence induction analysis is that most work done to date has used only qualitative or semiquantitative data analysis by visually comparing traces to observe the effects of different chemicals or treatments. Although this method is useful to observe major changes, a quantitative method must be used to detect more subtle, yet important, differences in the fluorescence induction trace. To achieve this, we used a relatively simple mathematical approach to extract the amplitudes and half-times of the three major fluorescence induction phases obtained from traces measured in thylakoid membranes kept at various temperatures. Apparent activation energies (E(A)) were also obtained for each kinetic step. Our results show that each phase has a different E(A), with E(A O-J)