Root Plasma Membrane Lipid Changes in Relation to Water Transport in Pepper: a Response to NaCl and CaCl2 Treatment

Seeds ofCapsicum annuum were grown hydroponically in a nutrient medium with or without NaCI and with supplemented Ca²⁺. Plasma membranes were isolated from roots using a two-phase aqueous polymer technique. The lipid composition (fatty acids, phospholipids and sterols) of the purified plasma membrane was determined. In the presence of NaCI, changes in lipid composition were shown, driving the membrane to a more rigid state. This was accomplished by an increase of (i) the saturation of fatty acids, (ii) the content of stearic acid versus palmitic acid, and (iii) the sterols concentration in the membrane. The changes in the phospholipid composition were also related to NaCI, which reverted when Ca²⁺ was also present in the nutrient solution. Furthermore, the alterations of plasma membrane lipid composition under salinity and calcium can be related to water transport properties of the membrane, but other physiological responses have to be taken into account.