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

The dehydration tolerance of leaf membranes of three coconut palm (Cocos nucifera L.) cultivars with different levels of resistance to drought stress in the field was evaluated by analysis of membrane lipids. Young plants, grown singly in pots, were subjected to controlled dehydration by witholding watering. The composition of coconut leaf lipids was similar to that of higher plants of the 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 and of monogalactosyl diacylglycerol was revealed, suggesting a high membrane tolerance to desiccation in Cocos. The fatty acid composition of the major phospholipid (phosphatidylcholine) was markedly enriched in alpha-linolenic acid in response to water deficit, suggesting a slowing down of monogalactosyl diacylglycerol biosynthesis and/or an adaptation to drought stress. (C) 1997 Elsevier Science B.V.