Vol. 11, Special Issue 8 (2022)

Author(s):
Nawale Archana Bhausaheb, Soundarrajan Vadivel, Geethalakshmi Vellingiri, Gnanam Ramasamy, Manikanda Boopathi Narayanan, Saranya Nallusamy, Thangaraj Kandasamy, Yogameenakshi Parameswaran and Meenakshisundaram Palaniappan

Abstract:
In the present study, seven different rice varieties, viz., N22, CO51, TKM13, ASD16, Kuliyadichan, Nootripathu and Sivappu Chithiraikar were studied for assessing diurnal fluctuations (under controlled conditions) as well as the effects of heat stress on catalase activity. Comparisons of mean catalase activity in control samples during different time periods viz., morning (6 a.m.), afternoon (1 p.m.) and evening (6 p.m.) revealed the existence of diurnal fluctuations. Catalase activity was found to increase from morning through afternoon and then dropped back to levels observed in the morning, but at different rates. This reveals that rice varieties exhibit diurnal fluctuations at varying rates. Based on the pairwise comparisons of mean catalase activity under different time and temperature conditions, it was found that catalase activity was affected by exposure to heat stress and rice varieties were having differential response. All varieties, but for N22, had elevated catalase activities upon heat stress showing that they are highly susceptible to ROS damage. Among the six varieties, CO51 exhibited significant differences in catalase activity. Based on the present investigation, molecular evidence is presented to support that N22 is a globally accepted heat tolerant variety and CO51 could be declared as heat susceptible rice variety. All other varieties have different degrees of heat tolerance and heat tolerance mechanisms are complex.