Antioxidative System as Influenced by High Temperature stress in Brassica juncea (L) Czern & Coss

The present investigation was undertaken to study the changes in antioxidative enzymes, lipid peroxidation and metabolites under heat stress and its revival in B. juncea genotypes (Thermo-tolerant BPR-542-6 and thermo-susceptible RGN-152). The activities of antioxidative enzymes viz. superoxide dismutase (SOD), ascorbate peroxidase (APX), glutathione reductase (GR), peroxidase (POX) and catalase (CAT) increased under high temperature stress upon revival. SOD and CAT started decreasing but activity of POX and GR still continued increasing in both the genotypes. But APX enzyme exhibited differential behaviour on revival which increased in tolerant genotype but decreased in susceptible genotype. Lipoxygenase (LOX), malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) which are the indicators of cell membrane damage increased under heat stress in both the genotypes but increase was higher in susceptible genotype. On recovery, LOX, MDA and H₂O₂ content decreased in both the genotypes. Ascorbic acid and carotenoids content increased under high temperature stress but during recovery, ascorbic acid continued increasing while carotenoids started decreasing in both the genotypes.