POLYPEPTIDE COMPOSITION, PIGMENT-PROTEIN COMPLEXES, AND FUNCTIONAL-ACTIVITY OF THYLAKOID MEMBRANES ISOLATED FROM HEAT-ACCLIMATED AND NONACCLIMATED PEA-PLANTS

The influence of higher temperatures on the polypeptide composition of thylakoid membranes and pigment-protein complexes, as well as on some parameters of their functional activity, in both acclimated and non-a cclimated young pea plants, was studied. Almost the whole set of polyp eptides in thylakoid membranes as well as in T40 particles was preserv ed after heat treatment (5 h, 55-degrees-C). During acclimation of the plants to high temperatures a reorganization of the photosynthetic ap paratus took place. In its thylakoids the oligomer/monomer ratio of th e photosystem (PS) 2 light-harvesting antenna was more than 50 % highe r compared to similar samples of the non-acclimated plants. After both the treatment of 5 h at 55-degrees-C only (non-acclimated plants) and that with step-wise increasing temperatures (acclimated plants), the PS1 activity was practically unchanged in all three variants, whereas the PS2 activity decreased more significantly in non-acclimated plants only.