The toxicological and physiological effects of various concentrations of Cadmium (Cd) and Nickel (Ni) on the different growth and physiological parameters viz. dry weight, biomass accumulation, weight of onion bulb, diameter of onion bulb and chlorophyll content of Allium cepa at different stages of growth was studied. Three different concentrations viz. T1 (25 ppm), T2 (50 ppm) and T3 (100 ppm) of Cd and Ni were used along with T0 control plant. Negative correlation was observed between different growth parameters and increasing concentration of Cd and Ni at all stages of growth. Toxic effects of heavy metal uptake in plants was clearly visible with wilting of leaves, decrease in weight and size of the onion bulb, decrease in biomass accumulation, decrease in the overall chlorophyll content. The intensity of such decrease increased with passage of time and increase in heavy metal concentration. Maximum toxicological effects were seen on 70 Days after sowing (DAS). Ni was identified as a potential inhibitor of photosynthesis. It was also seen that heavy metals compete with micronutrients and inhibit their uptake thus disturbing the growth and physiology of the plants.
