Growth response of Lemna gibba L. (duckweed) to copper and nickel phytoaccumulation Effet de l’accumulation de Cu et Ni sur la croissance de Lemna gibba L. (lentilles d’eau)

To assess the tolerance and phytoaccumulation ability of the duckweed Lemna gibba L. to copper (Cu) and nickel (Ni), the aquatic plants were exposed to different concentrations of Cu and Ni (0.1 – 2.0 mg/L) in quarter Coïc and Lesaint solution at pH = 6.0 (± 0.1) and under a daily regime of 12 h light. Copper and nickel were tolerated by L. gibba at concentrations ≤ 0.3 mg/L and ≤ 0.5 mg/L, respectively. However, plant growth decreased by 50% (I50) when the medium contained 0.45 mg/L of Cu or 0.75 mg/L of Ni. The observed LCI (lowest concentration causing complete inhibition) were 0.5 and 1.0 mg/L respectively in the presence of Cu and Ni. Results from metal analysis in plant tissues revealed a high accumulation of copper and a low accumulation of nickel within the plant (for concentrations causing no growth inhibition) and a corresponding decrease of metals in the water. The duckweed L. gibba L. could be a good candidate for the removal of low concentrations of copper from polluted water.