Influence of Cadmium, Lead and Zinc on the Growth and Metal Content in Ryegrass

Abstract

A greenhouse experiment was conducted to evaluate the effects of cadmium (Cd), lead (Pb) and zinc (Zn) on the growth and heavy metal content in ryegrass plants. The metals were applied separately at three different levels i.e. Cd at 10, 30 and 60 :g gG 1 ; Pb at 50, 100 and 150 :g gG 1 and Zn at 75, 150 and 225 :g gG 1 soil. Results demonstrated a significant inhibitory effect of metals on the growth and dry matter yields of ryegrass plants. The concentrations of metals both in roots and shoots increased significantly with Cd, Pb and Zn addition to the soil. The adverse effects of metals were more pronounced on roots than on the above ground plant parts. Among the tested metals, Pb displayed the greatest suppressing effect followed by Cd and Zn, indicating their relative toxicity in the order: Pb>Cd>Zn. It was suggested that the solubility of lead compound, presence of acetate in the soil medium, low pH of the soil and the relative tolerance of ryegrass to Cd were the factors contributing to the toxicity trend observed in the study.