Oxidative Damages by Chromium to Growth and Metabolism of Radish

The degree of oxidative damage and antioxidative response in leaves of radish (Raphanus sativus L), grown in refind sand treated with chromium from three sources were studied. The oxidative damage was maximum in dichromate treatment as maximum increases in lipid peroxidation and hydrogen peroxide concentration in leaves were observed. The growth of plants, biomass, iron concentration in different plant parts and chloroplastic pigment concentration in leaves were decreased in Cr^VI treated plants. Excess Cr led to increase in Cr concentration more in roots than shoot and to the development of toxicity symptoms; stimulated the activities of superoxide dismutase (SOD), ascorbate peroxidase (APX) and peroxidase and inhibited catalase activity when exposure was given for 7 days. Chromium (Cr^VI) toxicity in radish was also associated with decreased relative water content (RWC), degree of succulence, specific water content, leaf water potential (Ψ), and increased proline content. Observed results suggested that Cr^VI is more toxic than Cr^III and dichromate is more damaging than chromate because of the presence of two atoms of Cr in each molecule of dichromate and is less stable so it decomposes faster than chromate. The water stress parameters reported here in Cr^VI stressed radish plants indicate that plants exposure to excess supply of Cr reduces the physiological availability of water.