Influence of nutrient addition on growth and accumulation of cadmium and copper in Lemna gibba

Abstract

Aquatic plants have been identified as potentially useful for accumulating and bioconcentrating heavy metals. This study was developed to test the hypothesis that nutrient enrichment enhances the metal tolerance of floating macrophytes. Relative growth rates (RGR), photosynthetic pigments (chlorophyll a, b and carotenoid), malondialdehyde (MDA) content, and electrical conductivity (EC) were measured in Lemna gibba exposed to different cadmium and copper concentrations in laboratory conditions. Relative growth rates were negatively correlated with metal exposure, but nutrient addition suppressed this effect. Photosynthetic pigment levels were negatively correlated with metal exposures, and nutrient addition attenuated chlorophyll decrease in response to metal exposures. MDA content and EC also showed sharp increases at higher concentrations, indicating oxidative stress. This study indicates that nutrient enrichment increases the tolerance of Lemna gibba to metals, and that Lemna gibba is a suitable candidate for the phytoremediation of low-level copper and cadmium pollution.