Abscisic acid induced electrolyte leakage in woody species with contrasting ecological requirements

To determine the relationship between drought, abscisic acid (ABA) levels, and membrane leakage, these aspects were studied in three woody species with contrasting ecological requirements. Physiological comparisons were made, during a 14-day drought-recovery cycle, on a drought resistant species, jack pine ( Pinus banksiana Lamb.), and two more drought susceptible species, black spruce ( Picea mariana (Mill) B.S.P.) and flooded gum ( Eucalyptus grandis W. Hill ex Maiden). As the xylem pressure potentials (Ψ), declined under drought, both foliar ABA and electrolyte leakage increased significantly. However, ABA increased prior to the increase in leakage, and there was a significant linear correlation between endogenous ABA and leakage in all 3 species. Addition of exogenous ABA to the bathing solutions also significantly increased leakage of both unstressed and (sorbitol) osmotically-stressed leaf segments in response to increasing (log) concentrations of (±) cis-trans ABA [0–10.0 μ M ]. Electrolyte leakage in black spruce and flooded gum was more sensitive to stress-induced ABA than in jack pine. The results suggest that drought increases foliar ABA which initiates membrane leakage, and that sensitivity of membranes to ABA accumulation varies, depending on the ecological requirements of a species.