The impact of EDTA on lead distribution and speciation in the accumulator Sedum alfredii by synchrotron X-ray investigation

The in vivo localization and speciation of lead (Pb) in tissues of the accumulator Sedum alfredii grown in EDTA–Pb and Pb(NO3)2 was studied by synchrotron X-ray investigation. The presence of EDTA–Pb in solution resulted in a significant reduction of Pb accumulation in S. alfredii. Lead was preferentially localized in the vascular bundles regardless of treatments but the intensities of Pb were lower in the plants treated with EDTA. Lead was predominantly presented as a Pb-cell wall complex in the plants regardless of its supply form. However, a relatively high proportion of Pb was observed as Pb–EDTA complex when the plant was treated with EDTA–Pb, but as a mixture of Pb3(PO4)2, Pb–malic, and Pb–GSH when cultured with ionic Pb. These results suggest that EDTA does not increase the internal mobility of Pb, although the soluble Pb–EDTA complex could be transported and accumulated within the plants of S. alfredii.

Research highlights
► The plants of S. alfredii are less effective in taking up Pb from the EDTA–Pb medium.
► Pb is mainly localized in the vascular bundles and probably as Pb-cell wall complex.
► EDTA does not increase the internal mobility of Pb within the plants of S. alfredii.
► The Pb–EDTA complex could be transported and accumulated within the plants.