PHENOTYPIC ADAPTATION TO ELEVATED-TEMPERATURES OF TONOPLAST FLUIDITY IN THE CAM PLANT KALANCHOE-DAIGREMONTIANA IS CAUSED BY MEMBRANE-PROTEINS

Comparative electron paramagnetic resonance spectroscopic studies on s pin-labeled native and protein-free purified tonoplast membranes in th e CAM plant Kalanchoe daigremontiana showed that the phenotypic decrea se in tonoplast fluidity occurring up on acclimation to elevated tempe rature is brought about by specific protein-lipid interaction. However , there are indications that, to some extent, the properties of the bu lk tonoplast lipids may also be affected by acclimation to high temper ature. In contrast to heat acclimated individuals and for still unknow n reasons, in plants grown at normal temperature depletion of the tono plast membrane of its proteins had no effect on membrane fluidity. The results are considered as evidence for the occurrence of homeoviscous adaptation in the tonoplast of CAM plants towards changes in the temp erature climate during growth.