Effects of Cadmium and Combined Cadmium-Zinc Concentrations on Rooting and Nutrient Uptake of Cowpea Seedlings Grown in Hydroponic

A hydroponic experiment was carried out to investigate the effect of cadmium treatments at (0.3, 0.6, 0.9 and 1.2 mg/l), zinc at (2, 4, 6 and 20 mg/l) and combined cadmium-zinc at (0.6 mg/l Cd plus 2, 4, 6 and 20 mg/l Zn) on rooting, nutrient uptake in cowpea seedling. The results showed that increasing Cd supply markedly reduced the rooting of seedling. Increased Cd accumulation in cowpea seedling was observed as Cd concentration increased in culture media. Significant antagonistic effects of Zn on Cd concentration in the tissues occurred at levels above 4 mg/l in culture media. Zinc concentrations in the tissues decreased with increasing rates of applied Cd. Increasing Cd and Zn additions to the media resulted in increases in the concentration of Cd and Zn in plant tissues. It could be concluded that the reduction in Cd uptake caused by Zn addition might result from the competitive transport and absorption interaction between these two ions.