Effect of complete submergence on the activity of starch phosphorylase enzyme in rice (Oryza sativa L.) leaves

Effect of submergence on the activity of starch phosphorylase was studied in 25-day-old seedlings of four rice cultivars, viz. FR 13A and FR 43B as tolerant and Tulasi and Mahsuri as susceptible to submergence stress. After an initial decrease on the second day, the enzyme activity increased by 14 to 18 fold in the tolerant and 2 to 4 fold in the susceptible types on the fourth day of submergence. Thereafter, the activity decreased sharply. Concomitant with this there was fast depletion (50 to 64%) of starch reserve in both tolerant and susceptible cultivars, However, while in the tolerant cultivars 52 - 57% depletion occurred on the fourth day of submergence, in the susceptible ones 42 - 60% depletion occurred on the second day itself.