Response of Lemna minor L.(Duckweed) to the heavy metal copper

Present study aims to assess the tolerance and toxic effect of copper on common duckweed aquatic plant Lemna minor. Copper tolerance in Lemna minor was investigated under hydroponics conditions between pH of 4.5 to 6.7 and natural photoperiod. For toxicity test lemna minor L. were exposed to different concentration of CuSO4 (0.5, 1.0, 2.0, 4.0 mg/l and control) for measurement of frond numbers, general appearance and chlorophyll content. CuSO4 exposure caused chlorosis and necrosis in all test groups. Frond dissociation was noticed at 1.0 mg/l, chlorophyll content was found decreased in all concentration and was maximum at 4.0 mg/l concentration. Severity of symptoms was found toxicant concentration dependent. Possible mechanisms of copper toxicity to these valuable bioindicators have been discussed. The purpose of this study was to investigate the tolerance to copper in duckweed as a first step to determine the use of this aquatic species to remove heavy metal from polluted river water.