Potential of sunflower, castor bean, common buckwheat and vetiver as lead phytoaccumulators

English. ABSTRACT Studies concerning the tolerance, absorption and distribution of heavy metals in plants are essential for the success of phytoremediation programs. The present study was carried out in order to evaluate the potential of the sunflower, castor bean, common buckwheat and vetiver as lead phytoaccumulators. The species were grown in nutrient solution containing increasing doses of Pb (0, 50, 100, 200 and 400 mg L-1) during a 30-day exposure period. A completely randomized split-plot design was used, with a 4 x 5 factorial and three replicates. Significant reductions of dry matter of the root, shoot and whole plant were found in the all species under study as a function of the increased Pb doses. Vetiver showed higher tolerance to Pb contamination; sunflower and castor bean had intermediate tolerance and the common buckwheat proved to be the most sensitive species. The concentration and total content of Pb in plant compartments were significantly affected by the increased Pb doses in solution, and higher accumulation of this element was observed, in general, in the roots of the studied species. Common buckwheat proved to be not much promising for Pb-phytoremediation programs; sunflower showed potential for Pb phytoextraction and castor bean and vetiver were the most appropriate for Pb phytostabilization.

Portuguese. RESUMO Estudos sobre a tolerância, absorção e distribuição de metais pesados em plantas, são essenciais para se obter sucesso em programas de fitorremediação. O objetivo foi avaliar o potencial de girassol, mamona, trigo mourisco e vetiver como fito-acumuladoras de chumbo (Pb). As espécies foram cultivadas em solução nutritiva com doses crescentes de Pb (0, 50, 100, 200 e 400 mg L-1) durante 30 dias. O delineamento empregado foi o inteiramente casualizado em parcela subdividida com o fatorial 4 x 5, com três repetições. Foram constatadas reduções na matéria seca da raiz, parte aérea e planta inteira das espécies estudadas em resposta à elevação das doses de Pb. O vetiver mostrou a maior tolerância ao Pb, a mamona e o girassol apresentaram tolerância intermediária e o trigo mourisco se mostrou a espécie mais sensível. Os teores e conteúdos de Pb nos compartimentos das plantas aumentaram com a elevação das doses de Pb, tendo sido verificado, de forma geral, maior acúmulo deste elemento nas raízes. O trigo mourisco mostrou-se pouco promissor para programas de fitorremediação de Pb, o girassol apresentou potencial para fitoextração de Pb e a mamona e vetiver se mostraram mais adequadas para fitoestabilização desse elemento.