Efeitos da toxicidade do zinco em folhas de Salvinia auriculata cultivadas em solução nutritiva

Abstract

The aquatic macrophyte Salvinia auriculata has been used in several monitoring programs in bodies of water susceptible to eutrophication, being thus considered a bioindicator. However, salvinia is also known to have phytoremediating potential, accumulating considerable concentrations of pollutants in its tissues. Thus, this work aimed to evaluate the potential of this plant as a phytoremediator and bioindicator by analyzing its morphologic characteristics when submitted to Zinc (Zn) overdoses, as well as to determine the level of this metal accumulated in its tissues. The individuals were collected in water bodies free from contamination and cultivated in vases, using a nutrition solution, under controlled greenhouse conditions and submitted to treatments with Zinc in the form of ZnSO4. 7H2O at the following concentrations: 0; 2.5; 5.0; 7.5 and 10.0 mg L-1 . The morphologic alterations were observed daily and after ten days of exposure of the plants to Zinc, the number of individuals per treatment was counted. The plants were then harvested, washed, dried, weighed, ground and digested in a nitric and perchloric acid solution, with extracts being obtained for determination of the Zinc levels by atomic absorption spectrophotometry. The results indicated that S. auriculata presented morphologic damage, with the development of lesions and marginal necrosis on the leaves with Zinc concentrations, in solution, being superior to that allowed by the legislation, but not different in relation to the population growth. Zinc absorption by the S.auriculata plants increased proportionally to the concentration of the metal in the solution. When at high concentrations, Zinc became toxic to the plants, with their morphologic alterations being easy to detect, allowing them to be used in monitoring Zinc-polluted aquatic ecosystems.