Effect of Heat Stress on Antioxidative Defense System and Its Amelioration by Heat Acclimation and Salicylic Acid Pre-Treatments in Three Pigeonpea Genotypes

In this study, effect of heat stress on antioxidative defense system and its amelioration by heat acclimation and salicylic acid pre-treatments in three pigeonpea genotypes at seedling stage was analyzed. Heat acclimation (45°C for 3h) and salicylic acid (0.5 mM and 1 mM for 3h) pre-treatments were given to seven days old seedlings. Heat stress resulted in oxidative stress through the production of reactive oxygen species (ROS) mainly H₂O₂ and increased peroxidation of lipid membranes (MDA content). These pre-treatments conferred protection against heat stress through reduction in MDA and H₂O₂ content by means of induced adaptation effect and antioxidant activity which enhanced tolerance towards heat stress. Antioxidative defense system was observed through increased activity of CAT (average 1.02 fold increase in heat acclimated, 0.77 fold in 0.5 mM SA and 1 fold in 1 mM SA) and POX (average 1.30 fold increase in heat acclimated, 1.24 fold in 0.5 mM SA and 1.37 fold in 1 mM SA) in all genotypes. Among the three genotypes, AL 1931 performed best and acquired maximum thermotolerance.