Mechanisms of the temperature damage and acclimation of the photosynthetic apparatus

Abstract

Results about the influence of high temperature and heat acclimation on the formation and functional activity of photosynthetic apparatus are summarized. It was found that during the first hours of greening of barley and bean seedlings temperatufes up to 42°C accelerated chlorophyll biosynthesis and its destruction, especiallychlorophyll b after repeated darkening. Thermostability of photosynthetic apparatus depends on plant physiological state. Physiologically younger primary leaves of decapiPated plants have more thermostable thylakoid membranes in comparison with non-decapitated (intact) plants. An enhanced ability of bean plants (especially young ones) for acclimation to high temperature was established. Thermostability of the photoinduced transmembrane proton gradient ensuring membrane energBzation, and correlating with it the slow phase of millisecond component of delayed fluorescence considerably increased. Heat acclimation does not significantly influence the temperature of inactivation of O 2 -evolving system. The biosynthesis of lipids, especially of galactolipids, was strongly influenced during high temperature stress. Plant thermal acclimation was accompanied by accelerated biosynthesis and accumulation of DGDG and their specific molecular species. The mechanisms of heat damage and heat acclimation of photosynthetic apparatus are also discussed.