Comparative Growth and Distribution of Zn, Cd and Pb in Rice, Vetiver and Sunflower Grown in Contaminated Soils

Abstract

The effect of soil heavy metal (Zn, Cd and Pb) concentration on the growth and concentration in the plant parts of rice, vetiver and sunflower was comparatively investigated in pot experiments. Each plant species was grown in soils contaminated with four levels of heavy metals, based on a completely randomized design with three replications. Vetiver plants were harvested at 120 d after planting. Rice and sunflower plants were harvested at the yield stage. The results indicated that heavy metal in the soil showed an adverse effect on plant growth performances especially in rice. On moderately and highly contaminated soils, rice could not produce seed, while leaf chlorosis was observed at the tillering stage. In general, the concentration of Zn, Cd and Pb in plant parts increased as the contamination levels in the soil increased and they accumulated more in the roots than in above-ground parts. However, the Cd concentration in sunflower seed was above the maximum level tolerated by livestock. The ability of plants to translocate heavy metals from the roots to the shoots as indicated by their transfer factor (TF) was in the order: rice<vetiver<sunflower. Vetiver and sunflower could move Zn more than Cd and Pb. However, only sunflower had Zn TF values greater than 1 for all levels of contaminated soil. Therefore, sunflower was a promising plant for Zn decontamination.