Oxidative Damage and Antioxidant Response in Chenopodium murale L. Exposed to Elevated Levels of Zn

Present study was carried out to investigate the effects of different Zn concentrations on growth and some antioxidant responses in Chenopodium murale L. The seeds were sown on the pots. 45-day plants were transferred to hydroponic solution containing 0.2 (control), 150, 300 and 600 mu M Zn. The plants were harvested at 6 days after applying Zn treatments and some parameters were evaluated including plant length, fresh weight, photosynthetic pigments, malondialdehyde (MDA), ascorbate, proline and enzymatic antioxidants such as catalase (CAT), guaiacol peroxidase (GPX) and superoxide dismutase (SOD). Zn concentration showed a considerable increase in the shoot and root as the concentration of Zn increased in the medium, meanwhile the roots were characterized by higher Zn accumulation. At 150 mu M Zn, the length and fresh weight did not show important changes compared to the control, but these parameters decreased at 300 and 600 mu M Zn. With increasing Zn doses, the content of total chlorophyll declined, and also the content of carotenoids elevated. Excess Zn led to an increase in lipid peroxidation, free proline and ascorbate pool. Moreover, elevated Zn levels enhanced the activities of CAT, GPX and SOD. C. murale probably tolerates Zn concentrations up to 150 mu M using the production of carotenoid, proline and ascorbate as well as enhanced activity of enzymatic antioxidants. Higher Zn treatments seem to be toxic due to a severe decline in growth.