Kinetic Model of Electron-Transport Reactions in Thylakoid Membranes Determining Chlorophyll Fluorescence Transients

ABSTRACT

The analysis of chlorophyll fluorescence transients is very informative approach for evaluation of the physiological state of the photosynthetic machinery of higher plants. Tsimilli-Mishael and Strasser (2008) proposed a system (JIP-test) using the fluorescence transients for calculation of values of energy flows and yields at different stages of the photosynthetic process. In our paper a new model approach is developed for determination of electron transfer rate constants for different sites of the electron transfer chain using the same chlorophyll fluorescence transients. Two kinetic models of the photosynthetic process are constructed. The first one simulates the JIP-test and describes processes determining the three phases of the fluorescence transients during the first second of induction: primary photochemical reaction, electron transfer in the acceptor sides of Photosystem II (PS II) and of PS I. The second model includes most of the components of the electron transfer chain from PS II donor side to PS I. The fitting of the model to real transients allows the determination of rate constant values. Special software Modelyzer for numerical analysis of models is developed. The models are used for analysis of leaves from control plants and others with photosynthetic activity modified as a result of inhibition of electron transport by the herbicide 3-(3,4- dichlorophenil)-1,1-dimethylurea in barley plants—wild type and chlorophyll b-less Chlorina f2 mutant. A good correlation between model values of rate constants with JIP-test results is observed.

Keyword:

• JIP-test
• Mathematical modeling
• Photosystem II
• Variable chlorophyll fluorescence