Changes induced by Cu2+ and Cr6+ metal stress in polyamines, auxins, abscisic acid titers and antioxidative enzymes activities of radish seedlings

The present study determined the effects of copper and chromium metals on the endogenous titers of polyamines, auxins, abscisic acid and antioxidative enzyme activities in Raphanus sativus L. cv. Pusa chetki seedlings. Among polyamines, putrescine and spermidine contents were enhanced by Cu2+ metal to 62.44 and 402.8 µg g-1 f.w. respectively over control. Spermine which was not observed in control was recorded in highest concentration (1287.9 µg g-1 f.w.) in Cu2+ metal stressed seedlings. On the other hand Cr6+ metal treated seedlings showed reduced contents of putrescine (1.43 µg g-1 f.w.), cadaverine (0.09 µg g-1 f.w.), spermidine (277.99 µg g-1 f.w.) and spermine (2.29 µg g-1 f.w.) when compared to control and Cu2+ metal treated seedlings. Significant decline in free and bound IAA concentration were found under Cu2+ and Cr6+ metal stress when compared to control. Naphthalene acetic acid not recorded in control seedlings was detected in seedlings treated with Cu2+ and Cr6+ metal. Activities of guaiacol peroxidase and catalase were reduced significantly under Cu2+ and Cr6+ metal stress in comparison to control. Superoxide dismutase activity enhanced significantly under Cr6+ rather than Cu2+ metal treatment. In addition the phytotoxicity of Cu2+ and Cr6+ metal on seedling growth was also determined. The data suggest that Cr6+ is more phytotoxic than exposure to Cu2+ metal.