Accumulation and detoxification of lead ions in legumes.

This study focuses on lead accumulation in roots, stems and leaves of three plant species of the Fabacea family: Vicia faba, Pisum sativum and Phaseolus vulgaris grown hydroponically in a medium supplemented with 1 mM concentration of lead. The largest amount of lead, up to 75 mg Pb/g dry weight, was accumulated in roots of P. vulgaris. The highest rate of Pb ions uptake from the medium took place during the first 10 h of incubation with lead and after 96 h of incubation lead content in the medium decreased by half. Thus, it was suggested that P. vulgaris could be used in rhizofiltration--the use of plant roots to absorb pollutants from water contaminated with lead. At the same time we studied the influence of lead on acid soluble thiol, glutathione, homoglutathione contents and the synthesis of phyto- and homophytochelatins in roots of V. faba, P. sativum and P. vulgaris grown hydroponically. Activation of the detoxicative-phytochelatin system was observed in the cytosol of root cells of the tested plants. This system was composed of phytochelatins (PCs) in roots of V. faba, homophytochelatins (hPCs) in P. vulgaris roots and both PCs and hPCs in P. sativum roots. The total content of PCs and hPCs in roots of P. sativum was very high and reached around 4800 (expressed in nmol SH x g(-1)FW) and induction of their synthesis occurred after only 2 h of treatment with 1 mM Pb.