Growth response of Vernonia amygdalina Del planted in soil treated with a combination of cadmium, lead and zinc.

Abstract

Vernonia amygdalina Del. was grown (from stem cuttings) in soil polluted with a mixture of heavy metals; cadmium, lead and zinc. The mixture was in the ratio 1:1:1. The experiment consisted of control and four treatment concentrations (25, 50, 75 and 100 mg/kg) in three replicates. The cuttings were planted in untreated soil for one month prior to treatment. Data for growth parameters (plant height, number of leaves, leaf area, number of branches and girth) were collected monthly for 12 months, while physico- chemical and heavy metals analyses were carried out on soil samples at the end of the experiment. Plant samples were also analyzed for heavy metals content at this time. The results showed adverse effects of Cd+Pb+Zn treatment on the plant as manifested in the growth parameters, except leaf area which was enhanced. At the end of the study, control and the 25, 50, 75 and 100 mg/kg treatments had height values of 77.43±1.02, 40.27±0.75, 34.67±0.77, 26.23 ± 0.91, and 0.00 cm respectively. There was increase in soil acidity and soil carbon, with decreases in the soil nutrient element composition. The uptake of the metals was in the order Pb > Zn > Cd.