Resumen

OLIVEIRA, JURACI ALVES DE; CAMBRAIA, JOSÉ; CANO, MARCO ANTONIO OLIVA  y  JORDAO, CLÁUDIO PEREIRA. Cadmium absorption and accumulation and its effects on the relative growth of water hyacinths and salvinia. Rev. Bras. Fisiol. Veg. [online]. 2001, vol.13, n.3, pp. 329-341. ISSN 0103-3131.  http://dx.doi.org/10.1590/S0103-31312001000300008.

Cadmium absorption and  accumulation and its effects on the relative growth of water hyacinth (Eichhornia crassipes (Mart.) Solms)  and salvinia (Salvinia auriculata Aubl.) in nutrient solution were studied. Water hyacinth absorbed a significant higher amount of Cd than salvinia, and the difference between the species increased with the time of Cd treatment. The Km of Cd absorption, statistically similar in the two aquatic species when the leaves contacted the nutrient solution, became larger in salvinia when the leaves were not allowed to contact the absorption solution. The Vmax, on the other hand, was always larger in salvinia, independent of the contact or not of the leaves with the nutrient solution. The amount of adsorbed and absorbed Cd increased with the increase of Cd concentration, in both species, especially in salvinia, probably due to leaf contribution to uptake. The accumulation of Cd in the plants, high in the first 12 h, quickly decreased with the time of exposition to Cd, reaching stabilization after three days. Salvinia showed larger daily accumulation of Cd per unit of weight but water hyacinth larger total accumulation per experimental unit. Cadmium content increased with the increase in the time of treatment and with  Cd concentration in the nutrient solution, in both parts of the plant of the two species, especially in the roots. In water hyacinth about 80% of the total absorbed Cd accumulated in the roots, and that distribution did not change with the contact of the leaves with the nutrient solution. In salvinia, when the contact of the leaves with the nutrient solution was not allowed Cd distribution was similar to that observed in water hyacinth. When, however, the leaves contacted the nutrient solution about 50% of the absorbed Cd accumulated in that part of the plant. The relative growth decreased intensely with the increase in Cd concentration in both aquatic species, especially in salvinia. The concentration of Cd to reduce 25% in the relative growth rate was, on average, twelve times smaller in salvinia than in water hyacinth, due to its sensitivity to this  heavy metal.

Palabras llave : Heavy metals; cadmium tolerance; aquatic plants.