Kinetic analyses and mathematical modeling of primary photochemical and photoelectrochemical processes in plant photosystems

W.J. Vredenberg

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38 Citations (Scopus)

Abstract

In this paper the model and simulation of primary photochemical and photo-electrochemical reactions in dark-adapted intact plant leaves is presented. A descriptive algorithm has been derived from analyses of variable chlorophyll a fluorescence and P700 oxidation kinetics upon excitation with multi-turnover pulses (MTFs) of variable intensity and duration. These analyses have led to definition and formulation of rate equations that describe the sequence of primary linear electron transfer (LET) steps in photosystem II (PSII) and of cyclic electron transport (CET) in PSI. The model considers heterogeneity in PSII reaction centers (RCs) associated with the S-states of the OEC and incorporates in a dark-adapted state the presence of a 15–35% fraction of QB-nonreducing RCs that probably is identical with the S0 fraction. The fluorescence induction algorithm (FIA) in the 10 µs–1 s excitation time range considers a photochemical O-J-D, a photo-electrochemical J-I and an I-P phase reflecting the response of the variable fluorescence to the electric trans-thylakoid potential generated by the proton pump fuelled by CET in PSI. The photochemical phase incorporates the kinetics associated with the double reduction of the acceptor pair of pheophytin (Phe) and plastoquinone QA [PheQA] in QB nonreducing RCs and the associated doubling of the variable fluorescence, in agreement with the three-state trapping model (TSTM) of PS II. The decline in fluorescence emission during the so called SMT in the 1–100 s excitation time range, known as the Kautsky curve, is shown to be associated with a substantial decrease of CET-powered proton efflux from the stroma into the chloroplast lumen through the ATPsynthase of the photosynthetic machinery.
Original languageEnglish
Pages (from-to)138-151
JournalBiosystems
Volume103
Issue number2
DOIs
Publication statusPublished - 2011

Keywords

  • chlorophyll-a fluorescence
  • cyclic electron flow
  • single-turnover flash
  • induction kinetics
  • in-vivo
  • photosynthetic membrane
  • thylakoid membranes
  • spinach thylakoids
  • excitation-energy
  • reaction centers

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