Copper-induced toxicity in aquatic macrophyte, Hydrilla verticillata: effect of pH.

: Copper uptake and toxicity were evaluated in Hydrilla verticillata. Its effect on lipid peroxidation, chlorophyll, protein, ascorbate, cysteine and sugars was studied at pH 6.8. Dose- and durationdependent uptake of Cu followed by a significant decrease in malondialdehyde and sugar content was found in plant tissue. Chlorophyll, ascorbic acid and protein contents were increased non-significantly up to 8, 16 and 32 þM Cu, respectively. Cysteine content was slightly increased at lower concentrations followed by a significant decline. At 80 þM Cu, plants of H. verticillata showed significant toxic effects after 168 h of exposure indicating the sensitivity of the plant to this level of Cu stress. The effect of low and high pH in combination with different concentrations of Cu was determined at 168 h of exposure. Low pH (4.5) enhanced Cu toxicity while at high pH (9.5) toxicity was considerably reduced.