Effects of Gibberellic Acid on the Activation, Synthesis, and Release of Acid Phosphatase in Barley Seed

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Abstract
Acid phosphatase activity was present in unimbibed barley seed, but rose during incubation of embryoless half-seeds and isolated aleurone layers, and was further increased by 10−6 M gibberellic acid (GA3). Release of total acid phosphatase activity from half-seeds and aleurone layers was markedly enhanced by GA3. Inhibitor studies with cycloheximide and actinomycin D suggested that de novo synthesis of acid phosphatase occurred following imbibition. Gel nitration, electrophoresis, and [14C]leucine incorporation studies revealed that a single molecular form of acid phosphatase was present in dry seed, whereas on incubation two further forms arose. A proportion of the three molecular forms of the enzyme was synthesized de novo. Gibberellic acid stimulated activation, but not de novo synthesis, of all three molecular forms of acid phosphatase. Although a small amount of one of the molecular forms was secreted in the absence of GA3, the presence of gibberellin greatly increased secretion of the same form of acid phosphatase.