EDTA and Pb-EDTA accumulation in Brassica juncea grown in Pb-amended soil

Previous studies have shown that EDTA is necessary to solubilize soil Pb an d facilitate its transport from the soil to the above ground plant tissues. These studies have also suggested that Pb is accumulated in the plant tiss ue with transpiration as the driving force. We conducted further studies to evaluate the relationship between EDTA soil treatment, plant transpiration , and plant accumulation of Pb and EDTA. Indian mustard (Brassica juncea) plants were grown in soils containing Pb a t three different concentrations (1.5, 3.0 and 4.8 mmol/kg) for 5 weeks bef ore being treated with EDTA concentrations ranging from 0 to 10 mmol/kg. Pl ant shoots and xylem sap were collected and analyzed for Pb and EDTA conten t using ICP and HPLC, respectively. Water loss was measured for 7 days foll owing EDTA application. Transpiration was not affected at <5 mmol/kg EDTA b ut, at 10 mmol/kg EDTA transpiration decreased by 80%, whereas accumulation of Pb and EDTA increased. In the Sassafras soil, Pb and EDTA accumulation in the plant shoots continued to increase as the applied EDTA concentration increased, except at the highest level (10 mmol/kg). In soil amended with 4.8 mmol/kg Pb and 10 mmol/kg EDTA, the concentrations of EDTA and Pb in sh oots decreased and visible signs of phytotoxicity were observed. The result s presented herein support recent studies in hydroponic systems showing tha t EDTA and Pb are taken up by the plant and suggest that Pb is translocated in the plant as the Pb-EDTA complex. The results also show that the maximu m Pb accumulation by plants occurs by maximizing the concentration of the P b-EDTA complex based on the EDTA extractable soil Pb.