Phytoremediation of lead using Ipomoea aquatica Forsk. in hydroponic solution.

ABSTRACT

Ipomoea aquatica Forsk., an aquatic macrophyte, was assessed for its ability to accumulate lead (Pb) by exposing it to graded concentrations of this metal. Accumulation of Pb was the highest in root followed by that in stem and leaf with translocation factor (TF) values of less than unity. On the other hand, all bioconcentration factor (BCF) values in root, stem and leaf were greater than unity. Furthermore, exposure to Pb concentrations over about 20 mg L(-1) induced colour changes in the basal portion of stem which had significantly higher Pb accumulation than that in the unaffected apical part. This resulted in sequestration of excess metal in affected stem tissue, which could take up Pb by the process of caulofiltration or shoot filtration, and served as a secondary reservoir of Pb in addition to the root. The apical parts contained less lead and could regrow roots from nodes and survive when kept in Pb-free medium. The ability of the plant to store Pb in its root and lower part of stem coupled with its ability to propagate by fragmentation through production of adventitious roots and lateral branches from nodes raises the possibility of utilizing Ipomoea aquatica for Pb phytoremediation from liquid effluent.