Effects of an abscisic acid pretreatment on membrane leakage and lipid composition of Vigna unguiculata leaf discs subjected to osmotic stress

In leaf discs of Vigna unguiculata cv. EPACE-1 subjected to osmotic stress (PEG MW 8000, -1.3 MPa) a significant decrease in membrane integrity occurred, as evaluated by electrolyte efflux. This effect was significantly reduced when discs were treated with ABA (0.1 mM in Tris buffer) prior to PEG treatment. In PEG-treated discs, membrane lipids were drastically degraded, particularly the galactolipids. The percentage of linolenic acid in MGDG also decreased significantly. An ABA pretreatment of discs before osmotic stress significantly decreased galactolipid degradation and preserved their linolenic acid content. We concluded that ABA had a protective effect on membranes against osmotic stress, as attested by electrolyte leakage test and polar lipid analysis. Some possible roles for exogenous ABA in the acquisition of such an enhanced capacity to maintain membrane integrity under dehydration conditions are suggested. (C) 1997 Elsevier Science Ireland Ltd.