Backward electron transport in photosystem 2 reaction center and temperature dependence of delayed luminescence characteristics

The temperature dependence of parameters of light-induced changes in millisecond delayed luminescence (half-width of the maximum, maximal and steady-state luminescence intensity) is studied within the temperature range from -23 to 45 degrees C in leaf segments of Chinese rose (Hibiscus rosa sinensis). Delayed luminescence (DL) is induced and registered by a homemade setup based on a Lewis-Kasha-type phosphoroscope. The temperature dependence of steady-state luminescence intensity is shown to have two maxima, at -10 and 35 degrees C. At room temperatures, the steady-state value of luminescence intensity is minimal, and its value correlates with the temperature tolerance of the plant. Depending on cooling and heating regimes, the DL steady-state value vs. temperature curves is found to be different. We suppose this effect to be caused by temperature-induced destructive changes in the structure of photosystem 2 reaction centre and probably by salting out.     

The influence of sugar synthesis and transport rates on bioenergetics and kinetics of higher plant photosynthesis

We have obtained the theoretical dependences of stromal metabolite steady-state concentrations on external inorganic phosphate (P(i)) concentration. For this purpose, the theoretical model of photosynthesis, earlier described in [Ann. Appl. Biol. 138 (2001) 117], was modified to account for the regulation of starch formation by 3-phosphoglycerate (PGA) to P(i) ratio. When the rate constant of starch synthesis is taken to be independent on PGA/P(i) ratio, the steady-state concentrations of Calvin cycle metabolites and starch were found to change insignificantly as external P(i) concentration increases in wide range. However, as external P(i) range exceeds a critical value, the steady-state concentrations of all metabolites change abruptly. If the rate constant of starch synthesis depends on PGA/P(i) ratio, the steady-state concentrations of stromal metabolites change qualitatively in the same way with the increase of external P(i). However, no abrupt changes of metabolite and starch steady-state levels at high concentration of P(i) are observed. These results testify that the control of starch synthesis by PGA/P(i) ratio makes the photosynthetic system more stable in wide range of external P(i) concentrations.     

Study of temperature influence on electron transport in higher plants via delayed luminescence method: experiment, theory

The temperature dependence of steady-state millisecond delayed luminescence (DL) is studied within the temperature range from -23 to 45 degrees C in leaf segments of chinese rose (Hibiscus rosa-sinensis L.) and bean (Ficia faba). To describe the experimental dependence of DL steady-state intensity on temperature theoretically, we suggest the temperature dependences of rate constants in earlier proposed model of photosynthesis. Under these conditions, the temperature dependence of DL steady-state value has the same form as experimental curve.