Effects of Drought Stress on Enzymatic Breakdown of Galactolipids in Cowpea (Vigna unguiculata L.) Leaves

Abstract

Lipidic composition seems to be one of the main factors related to membrane resistance under water stress. Drought provokes a decrease in polar lipid content of leaves, the galactolipids (GL) being more affected than the phospholipids (PL) [1,2]. The decrease in GL content could be due to an increase in galactolipase activities and/or to a decrease in galactolipid biosynthesis. Studying two cultivars of Vigna unguiculata, Monteiro de Paula et al. [3] demonstrated that water stress stimulated the catabolism of galactolipids. These authors also found that changes in biosynthesis and degradation rates of leaf polar lipids were less pronounced in the drought-tolerant cultivar, possibly indicating a more stable cell membrane. Lipolytic acyl-hydrolases (LAH) and phospholipases play a major role in plant polar lipid degradation. Fatty acids (FA) resulting from LAH activity are the starting point for lipid peroxidation phenomena, which can in turn cause oxidation of membrane proteins and have damaging effects on the structure and function of the membrane. El-Hafid et al. [4] demonstrated that, in cotton leaves, LAH activities for ¹⁴C-MGDG increased under water stress.