Leaf membrane lipids and drought tolerance in young coconut palms (Cocos nucifera L.).

摘要

The dehydration tolerance of leaf membranes of coconuts cv. Malayan Yellow Dwarf, Cameroon Red Dwarf (both drought-susceptible) and Malayan Yellow Dwarf X West Coast Tall (drought-resistant) with different levels of resistance to drought stress in the field was evaluated by analysis of membrane lipids. Young plants, grown singly in pots in the Ivory Coast, were subjected to controlled dehydration by withholding watering. The composition of coconut leaf lipids was similar to that of higher plants ofthe so-called '18:3 (alpha-linolenic)' group, although the total lipid content was lower than that of herbaceous tropical crops. In response to drought stress, leaf total lipid and chloroplastic major lipid (monogalactosyl diacylglycerol) contents decreased more markedly in the more drought-susceptible cultivars. Analysis of leaf lipids is thus proposed as an early screening test for tolerance to drought stress. Despite the decrease in lipid contents, no modification of the fatty acid composition of total lipid extract or of monogalactosyl diacylglycerol was revealed, suggesting a high membrane tolerance to desiccation in coconuts. The fatty acid composition of the major phospholipid (phosphatidylcholine) was markedly enriched in alpha-linolenic acidin response to water deficit, suggesting a slowing down of monogalactosyl diacylglycerol biosynthesis and/or an adaptation to drought stress.