Oxidative stress induced by HCH in Hydrilla verticillata (l.f.) Royle: modulation in uptake and toxicity due to Fe

The effect of hexachlorocyclohexane (HCH) singly and in combination with iron was studied on chlorophyll, malondialdehyde, cysteine, total -SH contents and potassium ion leakage in the plants of Hydrilla verticillata. The effect of HCH was also studied on glutathione (reduced and oxidised) content and superoxide dismutase activity. The results showed an increase in malondialdehyde content and potassium ion leakage with increase in HCH concentrations, however, the presence of Fe played a protective role. The chlorophyll content was decreased with increase in HCH concentrations and exposure period. However, the chlorophyll content at 2 and 5 microg ml(-1) was significantly higher in HCH-treated plants as compared to HCH + Fe after 168 h, showing protective role of Fe. The results showed significant increase up to 1 microg ml(-1) in cysteine content with increase in concentrations in both the treatments. The total -SH content was increased with increase in concentrations in both the treatments. In HCH-treated plants, non-significant change was noticed in reduced glutathione (GSH) content however, oxidised glutathione (GSSG) content was increased significantly after 168 h, indicative of oxidative stress. In addition, superoxide dismutase activity was increased non-significantly with increase in HCH concentrations. The accumulation of HCH singly and in presence of Fe was concentration- and duration-dependent. The accumulation of HCH was decreased in presence of Fe at higher concentrations. In contrast, the accumulation of Fe was increased in presence of HCH at higher concentrations. The results showed that malondialdehyde content and potassium ions leakage are the primary responses of toxicity.