The role of gibberellic acid in the hydrolysis of endosperm reserves in Zea mays.

Excised maize (Zea mays L.) endosperms incubated in buffer rapidly degrade their starch and protein reserves. These processes are not markedly stimulated by addition of gibberellic acid (GA3). However protease and α-amylase production are strongly inhibited by abscisic acid, and this inhibition can be overcome by exogenous GA3. Endosperms of a dwarf mutant maize (d 5), which is deficient in endogenous GA, produce only small amounts of protease and α-amylase. With these mutants oxogenous GA3 causes a 3-5fold stimulation in hydrolase production. Our interpretation of these results is that in many cases maize endosperms contain sufficient gibberellin to stimulate maximal hydrolase production and starch and protein breakdown.