EFFECT OF SALINITY ON LIPID-COMPOSITION, GLYCINE BETAINE CONTENT AND PHOTO-SYNTHETIC ACTIVITY IN CHLOROPLASTS OF SUAEDA-MARITIMA

Growth with or without NaCl, the lipid composition of the chloroplasts of the halophyte Suaeda maritima remains remarkably stable, the most significant difference concerning phosphatidylglycerol and DELTA-3-trans-hexadecenoic acid which clearly decreases in the absence of NaCl. The photosynthetic activity is consistently higher in the chloroplasts from the plants grown in high NaCl concentration and this difference increases with the age of the plants. The Hill activity remains stable in the two types of chloroplasts (isolated from plants grown with or without NaCl) while the photosynthetic CO2 fixation is higher in chloroplasts isolated from plants grown in presence of NaCl. Glycine betaine addition in the incubation medium delays the decrease of photosynthetic activity while NaCl stabilizes it. Addition of NaCl causes a very significant increase in photosynthetic activity. On the other hand, it is shown that chloroplasts from plants grown in high-salt medium contain a higher amount of glycine betaine but this compound is rapidly lost when chloroplasts are further incubated in vitro. It is concluded that in high-salt medium, a halophyte such as Suaeda maritima develops chloroplasts with a very high photosynthetic activity, but these chloroplasts are more fragile when incubated in vitro.