COPPER-INDUCED TOXICITY IN AQUATIC MACROPHYTE, HYDRILLA-VERTICILLATA - EFFECT OF PH

Copper uptake and toxicity were evaluated in Hydrilla verticillata. It s effect on lipid peroxidation, chlorophyll, protein, ascorbate, cyste ine and sugars was studied at pH 6.8. Dose- and duration-dependent upt ake of Cu followed by a significant decrease in malondialdehyde and su gar content was found in plant tissue. Chlorophyll, ascorbic acid and protein contents were increased non-significantly up to 8, 16 and 32 p M Cu, respectively. Cysteine content was slightly increased at lower c oncentrations followed by a significant decline. At 80 pM Cu, plants o f H. verticillata showed significant toxic effects after 168 h of expo sure indicating the sensitivity of the plant to this level of Cu stres s. The effect of low and high pH in combination with different concent rations of Cu was determined at 168 h of exposure. Low pH (4.5) enhanc ed Cu toxicity while at high pH (9.5) toxicity was considerably reduce d.