Biochemical basis of high temperature tolerance during germination in Indian mustard (Brassica juncea L.)

The present investigation was carried out under laboratory conditions with 10 genotypes of Indian mustard (Brassica juncea) to study the high temperature induced changes during germination in carbohydrates, activities of peroxidase, superoxide dismutase (SOD), amylase and nitrate reductase enzymes. The temperature regime significantly affected all the characters studied. The genotypes x temperature interaction effects were significant only for germination and peroxidase activity. Increased temperature promoted the SOD and peroxidase but decreased nitrate reductase and amylase activities. Decline in the carbohydrates utilization in seeds limited by reduced amylase activity might have led to reduced germination. Germination exhibited positive and significant relationship with the activities of amylase (r = 0.392**), nitrate reductase (r = 0.265*) and peroxidase (r = 0.506**) under high temperature regime. The regression analysis revealed that under high temperature regime, peroxidase and amylase enzyme activities were important contributors to germination accounting for 24.4% and 14.5%, respectively, of the total variability in seed germination.