Endogenous gibberellin A(1) level and alpha-amylase activity in germinating rice seeds

The role of endogenous gibberellin A(1) (GA(1)) in the induction of alpha-amylase activity was investigated during germination of rice (Oryza sativa L.) seeds. The level of endogenous GA(1) and the alpha-amylase activity in the seeds of normal rice, cv. Nipponbare, increased simultaneously from 3 days after the imbibition of water. The alpha-amylase activities in the dwarf rice, cv. Waito-C and Tan-ginbozu, were less than that in the normal rice. The level of endogenous GA(1) and alpha-amylase activity were decreased in proportion to the concentration of a growth retardant, uniconazole. The retardation in alpha-amylase activity caused by the treatment of uniconazole was recovered by the application of exogenous GA(1). These results indicate that the endogenous GA(1) biosynthesized de novo regulates alpha-amylase production in germinating rice seeds.