496:	Effect of micronutrient interactions on copper toxicity to Scenedesmus bijugatus.

Authors:	Nadiminty, Nagalakshmi(A)Majeti, Prasad, N V .(A)
Affiliations:	(A): Dept. of Plant Sciences, University of Hyderabad
Presenter:	Nadiminty, Nagalakshmi , dpsrs@uohyd.ernet.in

Copper is a bioelement, but is toxic at high levels. Accumulation of copper in aquatic ecosystems poses a grave threat to fauna and flora as it participates in free radical-generating systems and causes oxidative stress. Aquatic organisms like algae or hydrophytes can be used as metal hyperaccumulators or as indicators of metal contamination. The response of Scnedesmus bijugatusto copper toxicity and the interactions of copper with micronutrients (Fe, Mn, Mo, Zn) were examined. The cells were: 1. Treated with Cu; micronutrient; and Cu + micronutrient. 2. Grown for 5 days in complete media; without micronutrient; without Cu; without both Cu & micronutrient and exposed to Cu. Growth, membrane lipid peroxidation and phosphate uptake were studied 0, 24, 48 and 72 hrs after Cu treatment. Zn had a synergistic effect with Cu after 48 hrs .The toxicity of Cu was more in cells grown in the absence of Cu alone and both Zn & Cu. Fe had a synergistic effect with Cu after 24 hrs. The toxicity of Cu was more in cells grown in the absence of Fe alone and Cu alone. Mn had a synergistic effect with Cu after 24 hrs. The toxicity of Cu was very high in cells grown in the absence of Mn alone and Cu alone. Mo had an antagonistic effect on Cu toxicity after 48 hrs. The toxicity of Cu was less in cells grown in the absence of Mo alone and Cu alone. Thus, the degree of Cu toxicity can be modified either negatively or positively by altering the levels of other micronutrients. Eventhough the interactions between elements in natural waters vary greatly, such systems offer a valuable tool in understanding the mechanisms of metal toxicity and tolerance.