Efectos del Ni, Zn y Cd sobre la morfología y el contenido de pigmentos de Lemna gibba L

Abstract

The present study aimed to study the phytotoxic effects of Nickel (Ni), Zinc (Zn) and Cadmium (Cd) on morphological characteristics and pigments of the macrophyte Lemna gibba. Ni decreased the area and the frond longitudinal and transversal axis from 0.37 mg/L and 0.92 mg/L respectively. Zn reduced these morphological parameters from concentration of 4.6 mg/L. Cd exerted effects on frond transversal axis at lower exposure concentrations (0.13 mg/L) than those affecting frond area (0.26 mg/L) and frond longitudinal axis (2.06 mg/L). Both Zn and Cd caused a desaggregation of colonies. The frond/colonies relation decreased from concentration of Zn of 20.1 mg/L an above, as metal concentrations increased. This effect was observed from 0.26 mg/L in the case of plants exposed to a gradient of Cd concentrations. A decrease in pigment content was observed for the three metals, with the exception of chlorophyll b and total carotenoids in the case of plants treated with Cd. Ni affected the pigment content in a greater extend. Long term toxicity endpoints (NOEC and LOEC) based on total area were the lowest values for the three metals, compared to those estimated based on frond number, indicating to be a good marker in the prediction of effects. Concentration-response curves showed a higher toxicity of Ni, followed by Cd with less toxicity exerted by Zn on plants of L. gibba. Fronds morphometrics characteristics together with frond/colonies relationships of L. gibba could be used in the early detection of effects of metals upon this macrophytes which plays an essential function on freshwater environments, as aquatic systems of Buenos Aires Province.