Tannins as gibberellin antagonists in the synthesis of alpha-amylase and Acid phosphatase by barley seeds.

The tannins chebulinic acid or tara tannin were added to an incubation system in which GA(3) induces enzyme synthesis in endosperm half seeds of barley (Hordeum vulgare L.). The activity of amylase and acid phosphatase in the incubation medium was reduced compared to the activity in the medium after incubation with GA(3) alone. When embryo half seeds of barley were incubated with chebulinic acid or tara tannin in the absence of added GA(3), the enzyme activity of the incubation medium was also reduced. The activity of preformed enzymes obtained from endosperm half seeds previously induced with GA(3) was not reduced by the addition of tannin. Comparisons were made of the amount of enzyme activity from breis of aleurone layers incubated with GA(3) in the presence and absence of tannins. The amounts of activity were relatively small and approximately equal in both cases, indicating that secretion from the aleurone was not blocked by the tannins. The reduction of enzyme activity caused by tannins in both endosperm and embryo half seeds could be completely reversed by the addition of GA(3).