Effects of dehydration and rehydration on the leaf lipids and lipid metabolism in Parkinsonia aculeata (Caesalpiniaceae)

Abstract

Plants of Parkinsonia aculeata L. were dehydrated by withholding water for 13 days and then rehydrated. The leaves of control plants and stressed plants were analyzed every four days from the beginning of stress and 6, 24, and 48 h after stress relief. Analysis of leaf water status showed a decrease in relative water content of nearly 16% during dehydration and a return to its control value after 48 h of rehydration. The contents of chlorophylls, chloroplast lipids (monogalactosyldiacylglycerol and digalactosyldiacylglycerol), and neutral lipids increased by 38%, 20%, and 125% (in μg·mg dry mass−1), respectively, when the daily decrease of relative water content reached 1.4%, while the mass of extra-plastidial lipids (phosphatidylcholine and phosphatidylethanolamine) increased by 25% (in μg·mg dry mass−1) only when the daily water loss was 2.6%. In addition, incorporation of radioactive acetate in lipids showed a preferential synthesis of digalactosyldiacylglycerol, phosphatidylglycerol, and phosphatidylcholine. The unsaturation degree of galactolipids remained stable, while a slight increase of unsaturation of phosphatidylcholine and phosphatidylethanolamine was observed. After rehydration, the mass of chlorophylls fell sharply, while the amount of total lipids decreased slowly as the level remained 17% higher than in the control 6 h after stress relief. Our results show that Parkinsonia plants are sensitive to a slight variation of the water potential and respond with an increased synthesis of membrane lipids during stress and after rehydration.