Gibberellic Acid Controlled Synthesis of α-Amylase in Barley Endosperm

Abstract

Because the endosperm half of a barley seed produces several hydrolytic enzymes in response to added gibberellins (1, 4, 5, 8), it is an attractive experimental system for a study of the mechanism of action of gibberellic acid. The only living cells in the half seed are those of the aleurone layers. These are an apparently homogeneous collection of respiring, nondividing cells which have the highly specialized function of producing and releasing some of those enzymes which are required to digest the starchy endosperm in preparation for its utilization by the growing embryo. Because the work of Paleg (5) had shown that the increase in a-amylase activity in barley endosperm halves is absolutely dependent upon added gibberellic acid and because a-amylase is heat stable and easily purified, a detailed study of the gibberellic acid triggered increase in a-amylase activity has been initiated.