Oxygenic Photosynthesis: Induction of Chlorophyll a Fluorescence and Regulation of Electron Transport in Thylakoid Membranes In Silico

The paper describes an extended mathematical model for the regulation of the key stages of electron transfer in the photosynthetic chain of electron transport and the associated processes of trans-thylakoid proton transfer and ATP synthesis in chloroplasts. This model includes primary plastoquinone PQ_A, associated with photosystem 2 (PS2), and secondary plastoquinone PQ_B, exchanging with plastoquinone molecules that are part of the pool of electronic carriers between PS2 and photosystem 1 (PS1). The model adequately describes the multiphase non-monotonic curves of chlorophyll fluorescence induction and the kinetics of P₇₀₀ redox transformations (photoreaction center PS1), plastoquinone, changes in ATP and pH concentrations in lumen (pH_i) and stroma (pH_o) depending on the illuminating conditions of chloroplasts (variation in intensity and spectral composition of light). The results of computer simulation are consistent with experimental data on the kinetics of photoinduced P₇₀₀ transformations in the leaves of higher plants and the induction of chlorophyll a fluorescence. The obtained data are discussed in the context of “short-term” mechanisms of pH-dependent regulation of electron transport in intact chloroplasts (non-photochemical quenching of excitation in PS2 and activation of the Calvin–Benson cycle reactions).