Effect of gibberrelic acid on α-amylase activity in heat stressed mung bean (Vigna radiata L.) seedlings

High temperature is a serious threat that can alter the number of biochemical processes in plants, which may lead to reduce crop yield. Gibberellic acid (GA 3 ) is a plant growth hormone, responsible for growth, stress tolerance and regulation of many enzymes like amylase. Amylase is responsible for growth by hydrolyzing starch into maltose. This experiment was carried out to study the effect of GA3 on a-amylase activity under heat stress conditions of four genotypes of mung bean (NM 19-19, NM 20-21, NM 121-123 and NCM 89). Seeds were sown in Petri dishes and incubated at different temperatures with and without 100 µM GA 3 . It was found that the lethal temperature was 50°C when exposed for 2 h and reduced β-amylase activity in all genotypes which increased when a mild temperature (40°C,1 h) prior to lethal temperature was given. The application of GA 3 can further alleviate the effect of heat stress by increasing β-amylase activity. Genotypic variations was also observed and activity of amylase and heat stress tolerance index was highest in NM 19-19 and lowest in NM 20-21 for all treatments. Key words : Mung bean, a-amylase, gibberellic acid, heat stress.