Effects of acclimation to low temperature and to water stress on photosynthesis and on physical and chemical properties of lipids from thylakoids of cucumber and cotton

The effects of growth at low temperature and under water stress on the physical and chemical properties of lipids of thylakoids from leaves of cucumber ( Cucumis sativis L. cv. Beit Alpha MR) and cotton ( Gossypium hirsutum L. cv. glandless Stoneville 213) were examined. The phospholipid transition temperature (measured by fluorescence polarization) was not different in cold-grown, water-stressed, or warm-grown control plants. These treatments also had no effect on the critical temperatures for chilling injury to photosynthetic oxygen evolution or for heat-induced increase in chlorophyll fluorescence. The molecular species compositions of cucumber and cotton thylakoid phosphatidylglycerols were compared to those of other chilling-sensitive plants and to those of plants able to acclimate. The acclimation treatments caused no changes in the phosphatidylglycerol molecular species of cucumber. However, in cold-grown cotton there was a marked decrease in the content of molecular species with high melting points. Collectively the results suggest that changes in phosphatidylglycerol molecular species composition are not always indicative of a critical process required for chilling resistance.