Abstract
Heavy metal allocation and the mechanism(s) of metal sequestration in different clonal organs, micro?domains and subcellular structures has not been systematically studied for rhizomatous perennial plants. It is thus pertinent to investigate the knowledge of the speciation and distribution characteristics of Cu in Phragmites australis to elucidating the mobility of metals in wetland plant after their uptake via root systems so as to facilitate the development of strategies to enhance Cu tolerance. ?This study investigated the distributions of Cu in Phragmites australis root, stem and leaf using ICP?MS, synchrotron?based X?ray micro?fluorescence and X?ray absorption spectroscopy, then evaluated the effects of Cu on cellular structure and ultrastructure via transmission electron microscope. ?The results indicate that a clear preferential localization of Cu in the root as compared with the shoots (stems and leaves), and the intensity of Cu in the vascular bundles was higher than that in the the surrounding epidermis and the endodermis and parenchyma outside the medullary cavity. The dominant chemical form of Cu in P. australis was similar to Cu?citrate. ?These results suggest that although Cu can be easily transported into the vascular tissues in roots and stems via Cu?citrate, most of the metal absorbed by plants is retained in the roots owing to its high binding to the cell wall, thus preventing metal translocation to the aerial parts of the plants. Therefore, P. australis showed a high capacity to accumulate copper in root, being therefore a suitable species for phytostabilization interventions.
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