Aleurone layers of barley contain large amounts of a soluble oligosaccharide which was identified as sucrose (30-40 μg/mg fresh weight). Treatment of the layers with gibberellic acid (GA3) causes the release of sucrose from the cells. This release requires the participation of metabolic processes, including protein synthesis. When embryoless half-seeds are incubated sucrose accumulates in the aleurone layers, but when seeds are germinated the sucrose content of the aleurone layers declines. Labeling experiments with radioactive glucose and fructose show that aleurone layers continuously synthesize sucrose and that the release, but not the synthesis of sucrose is enhanced by GA3.