Influence of Post-action of High Temperatures on Photosynthetic Activity, Composition of Lamellar Proteins and Spectral Characteristics of Pigment Systems I and II )

Abstract

Summary Post-action on photosynthesis in spinach leaves after heat-treatment for 5 min at 25, 40, 45 and 50 °C was studied. Samples for analyses were taken at 0, 24 and 48 h after treatment. It was found that the inhibitory action after 5 min treatment of the leaves at 40 and 45 °C was most strongly expressed immediately after the treatment. 24 h after treatment the variant at 40 °C almost restored its photosynthetic activity close to that of the control (25 °C). Restoration, though inconsiderable, was observed with the variant at 45 °C too, while at 50 °C the inhibition of photosynthesis was irreversible. The heat-treatments did not lead to significant changes in the composition of the structural proteins in chloroplast, including those which are components of pigment systems I and II. Even 48 h after leaf treatment at 45 and 50 °C (of which the first temperature very strongly inhibits and the second one completely eliminates photosynthesis) the electrophoretic profile of the structural proteins remained almost unchanged. No significant changes in spectral characteristics of the second derivate of the absorption function and the fluorescence spectra of photosystems I and II were observed. This indicates considerable stability of the bonds between pigment + pigment and pigment + protein.