DIFFERENTIAL BIOCHEMICAL RESPONSES OF BRASSICA JUNCEA TO CADMIUM STRESS: ANTIOXIDATIVE DEFENCE SYSTEM, PHOTOSYNTHESIS AND POLYPHENOL SYNTHESISDHRITI KAPOOR, ARBEEN AHMAD BHAT, RENU BHARDWAJ, SATWINDERJEET KAUR AND RAJNEESH ANANDAbstract Heavy metals are major environmental pollutants, which produce oxidative burst by generation of reactive oxygen species. They may cause toxic effects in living organisms by entering through food chain. Brassica juncea plants are hyperaccumulators of heavy metals and possess certain defensive strategies to scavenge the free radicals. The present study deals with the effects of cadmium (Cd) metal on growth, lipid peroxidation, metal uptake, antioxidative defence system, photosynthetic parameters, sugars, total phenolic content and level of polyphenols in 60 days old plants of Brassica juncea (var. RLC 1). It was observed that the growth of plants was retarded under Cd metal stress. Metal accumulation and malondialdehyde content was found to enhance with stress (90.05 8mol g-1 DW & 4.8mol g-1 FW respectively). The activities of antioxidative enzymes and contents of proteins and glutathione were also enhanced in plants subjected to metal stress. Adverse effects on photosynthetic parameters and alteration in the level of phenols during stress were analyzed by infra red gas analyzer (IRGA) and ultra performance liquid chromatography (UPLC) respectively. Ion chromatography exhibited the enhanced sugar level under stress conditions. Thus, it is concluded from present investigations that the levels of compatible solutes and antioxidative defence system of Brassica juncea got stimulated under Cd stress which facilitated the detoxification of the reactive oxygen species.
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