Abstract:
Experiments were conducted to investigate the phytotoxic effects of heavy metals on chickpea, grown in unsterilised soils. Cadmium at 23 mg/kg soil, when used alone or in combination with other metals, was found to be the most toxic and significantly (P ? 0.05) reduced the plant growth, nodulation, chlorophyll content, and root and shoot N contents. Cadmium (23 mg/kg soil) and lead (390 mg/kg soil) reduced the number of nodules by 69.2 and 13.7%, respectively. Cadmium at 5.75 and 11.5 mg/kg soil decreased the seed yield by 14 and 19%, respectively, compared with the control. In contrast, lead at 97.5 and 195 mg/kg soil increased the seed yield by 12.3 and 8.8%, respectively, above the control. Generally, the chlorophyll content decreased with increasing rates of each metal. The root and shoot N content decreased by 33.3 and 30.7% at 23 mg/kg of cadmium, whereas lead at 390 mg/kg soil increased the root and shoot N content by 10 and 3%, respectively, above the control. The grain protein decreased gradually with increasing rates of each metal. An average maximum reduction (27%) in grain protein was observed with mixtures of 23 mg cadmium + 135 mg chromium + 580.2 mg nickel per kg soil. Flowering in chickpea plants was delayed following metal application. The degree of toxicity of heavy metals on the measured parameters decreased in the following order: cadmium, zinc, nickel, copper, chromium, then lead. Accumulation of heavy metals was higher in the roots relative to the shoots of chickpea and was significantly correlated with the concentration of the metals added to the soil.