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.