|Effect of plant growth regulators and end-product on the enzyme activities in cotyledons of Vigna angularis during germination was investigated by measuring the changes of α-amylase activities in attached and detached cotyledons applied growth regulators and sugars. The higher levels of α-amylase in detached cotyledons than those in cotyledons attached to the embryonic axis were due to both faster synthesis and slower degradation of the enzyme in the detached cotyledons than in the attached cotyledons. Levels of α-amylase activity were reduced by high concentrations of glucose and sucrose, and it is suggested that this effect was caused mostly by osmotic stress and partly by end-product repression. In detached cotyledons exogenously supplied GA₃, IAA, kinetin, or their combinations has a small promotive effect on the developmental patterns of α-amylase activity. ABA and uniconazole both prevented the synthesis of α-amylase. Glucose inhibition of enzyme activity was partly reversed by the application of GA₃ and cAMP. GA₃ and cAMP seemed to act through a similar mechanism. The addition of inhibitors of protein and RNA synthesis largely prevented the increase of enzyme activity in the presence or absence of exogenous GA₃. The pretreatment experiments with canavanine indicated that the earlier the time of addition was, the lower the amylase activity was.