Citation: LIU Jian, LUO Li-Qiang. Analysis of Ultrastructure of Root Cell and Lead Speciation in Celery. Chinese Journal of Analytical Chemistry, 2018, 46(9): 1479-1485. doi: 10.11895/j.issn.0253-3820.181253 [复制]
Analysis of Ultrastructure of Root Cell and Lead Speciation in Celery
Plant cells are important biochemical reaction sites for responding to heavy metal stress. Exploring the distribution and speciation of lead (Pb) in celery at the cellular level is an important way to reveal the toxic mechanism of harmful elements on vegetables. In this study, ultrastructural alterations, localization of Pb in root cell and Pb speciation in celery were investigated by energy dispersive transmission electron microscopy (TEM-EDS) and X-ray absorption near edge spectroscopy (XANES). The result showed that Pb stress significantly changed the ultrastructure of celery root cells, increased intercellular spaces, thickened cell walls, and roughened plasma membrane. The roots, stems and leaves of celery had different speciation transformation functions for Pb, which could convert inorganic lead (Pb(NO3)2) into organic lead form. About 62.7% of Pb in celery root cells deposited in the cell wall as the form of Pb5(PO4)3Cl, which showed the tolerance and detoxification of plant for Pb. The organic lead (Pb(Ac)2·3H2O) in roots and stems were approximately from 34.4 to 37.3%, while total organic lead (Pb(C17H35COO)2 and Pb(Ac)2·3H2O) in leaves accounted for 63.3%. This study indicated that Pb-phosphate in plant cells was derived from the biosynthesis by plants rather than the external rhizosphere environment. Pb in the rhizosphere of celery could enter the root cell as the form of Pb-Ac complex, and a part of Pb was converted into Pb5(PO4)3Cl deposition in the cell wall to detoxify and tolerate of Pb, and a small part of Pb was transported to the leaves and accumulated as the form of macromolecular Pb-organic acid and Pb-phosphate.
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