The role of EDTA in phytoextraction of hexavalent and trivalent chromium by two willow trees

Abstract

Effects of the synthetic chelator ethylenediamine tetraacetate (EDTA) on uptake and internal translocation of hexavalent and trivalent chromium by plants were investigated. Two different concentrations of EDTA were studied for enhancing the uptake and translocation of Cr from the hydroponic solution spiked with K2CrO4 or CrCl3 maintained at 24.0 ± 1°C. Faster removal of Cr3+ than Cr6+ by hybrid willows (Salix matsudana Koidz × Salix alba L.) from the plant growth media was observed. Negligible effect of EDTA on the uptake of Cr 6+ was found, but significant decrease of the Cr concentration in roots was measured. Although the translocation of Cr6+ within plant materials was detected in response to EDTA concentration, the amount of Cr 6+ translocated to the lower stems was considerably small. EDTA in the nutrient media showed a negative effect on the uptake of Cr3+ by hybrid willows; the removal rates of Cr3+ were significantly decreased. Translocation of Cr3+ into the stems and leaves was undetectable, but roots were the exclusive sink for Cr3+ accumulation. Weeping willows (Salix babylonica L.) showed lower removal rates for both chemical forms of Cr than hybrid willows. Although EDTA had a minor effect on Cr6+ uptake by weeping willows, positive effect on Cr 6+ translocation within plant materials was observed. It was also determined that EDTA in plant growth media significantly decreased the amount of Cr3+ taken up by plants, but significantly increased Cr3+ mobilization from roots to stems. Results indicated that EDTA was unable to increase the uptake of Cr6+ by both plant species, but translocation of Cr6+-EDTA within plant materials was possible. Addition of EDTA in the nutrient media showed a strong influence on the uptake and translocation of Cr3+ in both willows. Cr3+-EDTA in tissues of weeping willows was more mobile than that in hybrid willows. The information has important implications for the use of metal chelator in plant nutritional research. © 2007 Springer Science+Business Media, LLC.