Planta

, Volume 223, Issue 1, pp 114–133

Chlorophyll a fluorescence induction kinetics in leaves predicted from a model describing each discrete step of excitation energy and electron transfer associated with Photosystem II

  • Xin-Guang Zhu
  •   Govindjee
  • Neil R. Baker
  • Eric deSturler
  • Donald R. Ort
  • Stephen P. Long
Original Article

DOI: 10.1007/s00425-005-0064-4

Cite this article as:
Zhu, XG., Govindjee, Baker, N.R. et al. Planta (2005) 223: 114. doi:10.1007/s00425-005-0064-4

Abstract

Chlorophyll a fluorescence induction (FI) is widely used as a probe for studying photosynthesis. On illumination, fluorescence emission rises from an initial level O to a maximum P through transient steps, termed J and I. FI kinetics reflect the overall performance of photosystem II (PSII). Although FI kinetics are commonly and easily measured, there is a lack of consensus as to what controls the characteristic series of transients, partially because most of the current models of FI focus on subsets of reactions of PSII, but not the whole. Here we present a model of fluorescence induction, which includes all discrete energy and electron transfer steps in and around PSII, avoiding any assumptions about what is critical to obtaining O J I P kinetics. This model successfully simulates the observed kinetics of fluorescence induction including O J I P transients. The fluorescence emission in this model was calculated directly from the amount of excited singlet-state chlorophyll in the core and peripheral antennae of PSII. Electron and energy transfer were simulated by a series of linked differential equations. A variable step numerical integration procedure (ode15s) from MATLAB provided a computationally efficient method of solving these linked equations. This in silico representation of the complete molecular system provides an experimental workbench for testing hypotheses as to the underlying mechanism controlling the O J I P kinetics and fluorescence emission at these points. Simulations based on this model showed that J corresponds to the peak concentrations of QAQB (QA and QB are the first and second quinone electron acceptor of PSII respectively) and QAQB and I to the first shoulder in the increase in concentration of QAQB2−. The P peak coincides with maximum concentrations of both QAQB2− and PQH2. In addition, simulations using this model suggest that different ratios of the peripheral antenna and core antenna lead to differences in fluorescence emission at O without affecting fluorescence emission at J, I and P. An increase in the concentration of QB-nonreducing PSII centers leads to higher fluorescence emission at O and correspondingly decreases the variable to maximum fluorescence ratio (Fv/Fm).

Keywords

Photosynthesis Chlorophyll fluorescence Model System biology In silico 

Copyright information

© Springer-Verlag 2005

Authors and Affiliations

  • Xin-Guang Zhu
    • 1
  •   Govindjee
    • 2
  • Neil R. Baker
    • 3
  • Eric deSturler
    • 4
  • Donald R. Ort
    • 1
  • Stephen P. Long
    • 1
  1. 1.Department of Plant Biology and Crop SciencesUniversity of Illinois at Urbana ChampaignUrbanaUSA
  2. 2.Department of Plant Biology and Department of Biochemistry265 Morrill HallUrbanaUSA
  3. 3.Department of Biological SciencesUniversity of EssexEssexUK
  4. 4.Department of Computer Science, 4314 Thomas M. Siebel Center for Computer ScienceUniversity of Illinois at Urbana ChampaignUrbanaUSA

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