The study of EDTA enhanced Cd accumulation and formation in Napier grass using synchrotron μX-ray fluorescence imaging and X-ray absorption spectroscopy

Abstract

In this study, Pennisetum purpureum, a fast growing and highly tolerant plant, was used as a Cadmium (Cd) hyperaccumulator associated with Ethylenediaminetetraacetic acid (EDTA). It was found that P. purpureum's shoots and roots grown in the presence of EDTA accumulated significantly higher Cd than those grown in the absence of EDTA. Synchrotron μX-ray fluorescence imaging demonstrated the significant Cd accumulation in the internal tissues of root: endodermis, xylem and phloem, while at stem, it was found at the external tissues: epidermis and phloem. Synchrotron X-ray Absorption Spectroscopy was used to characterize the Cd speciation in plant cells. P. purpureum was discovered to accumulate Cd (II) form. In order to determine the possibilities of Cd bonding in chemical compounds, linear combination fitting of Cd K-edge XANES spectra was carried out. The EDTA-free condition as a control revealed mainly Cd–N/O bonding ligand, while the EDTA-treated condition mostly showed Cd–N/O and Cd–S bonding. The overall results suggested that EDTA is a potential substance to enhance the efficiency of Cd absorption in P. purpureum.