CATIONIC MOBILIZATION IN BARLEY SEEDLINGS .1. EFFECT OF GIBBERELLIC-ACID

The exogenous application of gibberellic acid (GA3) stimulates the differential mobilization of Na+, K+, Mg++ and Ca++ cations from the grain into the shoot and root of barley (Hordeum vulgare L.) seedlings. The total amount of each cation varies depending on the GA3 concentration applied, being highest at 80 mg.l-1 for Na+, K+ and Ca, and at 8 mg.l-1 for Mg++. The main action of GA3 on cationic mobilization is that induced on both of the developing organs, more than that caused by the direct action of GA3 on the grain, which produces a liberation of the cations. The accumulation of cations in each organ of the seedling as a result of the GA3 applied is related more to dry weight than to total cation amount in the organ. In the root, the concentrations of K+, Mg++ and Ca++ reach a maximum at 80 mg.l-1 GA3, while the concentration of Na+ continues to increase at higher doses. Ca++ and especially Mg++, attain higher values than K+ and Na+. GA3 produces the opposite effect in the shoot than in the root reducing the cationic concentrations. The behavior of the cationic mobilizations studied suggests that they are related to the influence of the GA3 on the regulation of cell membrane permeability.