Copper tolerance and response of antioxidative enzymes in axenically grown Brassica juncea (L.) plants

Copper is an essential element for proper functioning of all living organisms including plants, but it can cause toxicity at elevated concentrations. In the present study, two varieties of Brassica juncea L. i.e. Pusa JK and TM 4 grown axenically were compared for Cu tolerance and accumulation ability. For further detailed biochemical studies, var. TM 4 was used because of its fast growth and better Cu accumulation in shoots. Toxic effects of Cu were manifested by a reduction in photosynthetic pigments and an increase in the levels of thiobarbituric acid reactive substances. The activities of antioxidant enzymes such as superoxide dismutase, ascorbate peroxidase, guaiacol peroxidase and catalase showed an increase in a concentration and exposure time dependent manner in roots of B. juncea exposed to copper, indicating that they play an important role in combating copper stress in this species.