The growth and developmental characteristics of grasses and their high biodiversity make such plants suitable for remediation of areas contaminated by heavy metals. Nevertheless, heavy metal toxic effect on the plants may cause alteration in their metabolic pathways, such as photosynthesis, respiration, and growth, modifying plant anatomy. This work aimed to evaluate the effect of levels of soil contamination (0, 7.5 % and 15 % m³ m-3) on biomass production, on photosynthetic characteristics and on anatomical changes in roots and leaves of brachiaria (Brachiaria decumbens Stapf.). After seeds were planted, seedlings were uprooted and replanted in vases containing soil at different contamination levels, being left to rest for 120 days. At the end of that time, plants presented reduced yield of root and shoot dry matter, contents of chlorophyll a, chlorophyll b, total chlorophyll and potential photosynthesis with increased of soil contamination. The cell layers of endodermis and exodermis in the root tissues and the cell walls of the xylem and cortical parenchyma all thickened as contamination increased. In the leaf tissues, the adaxial and abaxial epidermis presented increased thickness while the leaf blade presented reduced thickness as contamination increased with consequent change in the root growth rate. In general, the effects of heavy metal increased with the metal concentration. Some results indicate that B. decumbens seems to have some degree of heavy metal tolerance.

A poluição por metais pesados, gerada principalmente pelas atividades de mineração e industrial, exige estudos que possibilitem a recuperação de áreas contaminadas. Foram estudadas respostas de crescimento e características anatômicas de plantas jovens de salgueiro cultivadas em solo multicontaminado por metais pesados. As plantas foram cultivadas em três níveis de misturas de solo contaminado: 0%; 15% e 30% (v/v), durante 60 dias. No maior nível de contaminação foi observado menor produção de matéria seca das raízes e da parte aérea e menor crescimento das raízes. Nesta condição, as raízes apresentaram maior espessura da epiderme, exoderme e endoderme e menor número de elementos condutores de xilema. As folhas apresentaram modificações no número de elementos condutores de xilema, na densidade e diâmetro dos estômatos, e na espessura da epiderme, endoderme, colênquima e do mesofilo.

The heavy metal pollution caused mainly by mining and industrial activities requires studies for the recovery of contaminated areas. Thus, we studied growth and anatomical characteristics responses of young willow plants grown in heavy metal multicontaminated soil. Plants were grown in three mixture levels of contaminated soil: 0%, 15% and 30% (v/v) for 60 days. At the highest level of contamination was noted a less dry matter production of roots and shoots and reduced root growth. Accordingly, the roots exhibited epidermis, exodermis and endodermis thicker, and a smaller number of conducting elements of xylem. Leaves showed changes in the number of conducting elements of xylem diameter and density of stomata, and epidermis, endodermis, collenchyma and mesophyll cell thickness.