Heavy metal toxicity in legume-microsymbiont system

A pot study was conducted to investigate the toxicity of cadmium (Cd), lead (Pb), copper (Cu), zinc (Zn), chromium (Cr), and nickel (Ni) added separately or in combination on chickpea (Cicer arietinum L.)-Rhizobium and greengram (Vigna radiata (L.) Wilczek)-Bradyrhizobium systems and metal uptake pattern by legume grains. Chickpea-Rhizobium system was comparatively more sensitive to heavy metal toxicity than greengram-Bradyrhizobium system in terms of decreased yield, low nitrogen content in plant tissues, and the protein content in grains. The phytotoxicity was apparently due to the susceptibility of the symbiotic apparatus against toxic doses of heavy metals. Metal uptake by grains seemed to be directly related to the concentration of heavy metals and was greater in the case of an individual metal added separately than in combination.