Phenotypic Adaptation of Membrane Fluidity in the Tonoplast and Plasmalemma the C3 Plant Hordeum vulgare cv. Alexis

Summary The influence of growth temperature and salinity stress on the fluidity of the tonoplast and plasmalemma in Hordeum vulgare cv. Alexis was studied. Membrane fluidity was monitored by measurements of fluorescence polarisation in membrane vesicles labeled with the fluorescent fatty acid analogue 1,6-diphenyl- 1,3,5-hexatrien (DPH) as a probe. It was found that, both in the tonoplast and plasmalemma, an increase in growth temperature lowered membrane fluidity, whereas lowering of growth temperature did the opposite. There is evidence that the rigidization of the membranes due to increase in growth temperature is mainly caused by membrane proteins. Accumulation of salt in the vacuoles of plants did not significantly shift the fluidity of the membranes, neither in the tonoplast nor in the plasmalemma. The results suggest that phenotypic adaptation of membrane fluidity also occurs in the tonoplast and plasmalemma of C 3 plants, and not only in the tonoplast of CAM plants as previously reported.