Copper removal efficiency in a surface water and compartmentalization in the floating fern Salvinia minima

Abstract

In order to determine copper removal efficiency and compartmentalization in the free floating fern S. minima, a bioassay was performed in which plants were exposed to increasing copper concentrations in the range of 1 to 30 mg Cu L-1 for six days in Pilcomayo River surface water. S. minima accumulated the metal in a dose-dependent manner. Metal concentration was from 6.5 to 3.9 times higher in the submerged biomass in comparison to the aerial biomass in all treatments reflecting a poor mobility of copper between plant tissues. In both biomasses, most of the copper was localized in the extracellular compartment and increased lineally with increasing concentration of copper in water. The intracellular fraction increased following a polynomial function. The physicochemical characteristics of the experimental water influenced copper bioavailability inducing copper precipitation and the high concentration of calcium may have exerted a protective effect limiting metal entrance to cells. The values of the BCF and of the dry biomass weight that corresponded to copper showed that in Pilcomayo River water S. minima showed a copper removal efficiency not of a hyperaccumulator but of an effective accumulator.