In situ speciation and distribution of toxic selenium in hydrated roots of cowpea.
نویسندگان
چکیده
The speciation and spatial distribution of selenium (Se) in hydrated plant tissues is not well understood. Using synchrotron-based x-ray absorption spectroscopy and x-ray fluorescence microscopy (two-dimensional scanning [and associated mathematical model] and computed tomography), the speciation and distribution of toxic Se were examined within hydrated roots of cowpea (Vigna unguiculata) exposed to either 20 µM selenite or selenate. Based upon bulk solution concentrations, selenate was 9-fold more toxic to the roots than selenite, most likely due to increased accumulation of organoselenium (e.g. selenomethionine) in selenate-treated roots. Specifically, uptake of selenate (probably by sulfate transporters) occurred at a much higher rate than for selenite (apparently by both passive diffusion and phosphate transporters), with bulk root tissue Se concentrations approximately 18-fold higher in the selenate treatment. Although the proportion of Se converted to organic forms was higher for selenite (100%) than for selenate (26%), the absolute concentration of organoselenium was actually approximately 5-fold higher for selenate-treated roots. In addition, the longitudinal and radial distribution of Se in roots differed markedly: the highest tissue concentrations were in the endodermis and cortex approximately 4 mm or more behind the apex when exposed to selenate but in the meristem (approximately 1 mm from the apex) when exposed to selenite. The examination of the distribution and speciation of Se in hydrated roots provides valuable data in understanding Se uptake, transport, and toxicity.
منابع مشابه
In Situ Speciation and Distribution of Toxic Selenium in Hydrated Roots of Cowpea1[C][W]
The University of Queensland, School of Agriculture and Food Sciences, St. Lucia, Queensland 4072, Australia (P.W., N.W.M., B.A.M., P.M.K.); University of South Australia, Centre for Environmental Risk Assessment and Remediation, Mawson Lakes, South Australia 5095, Australia (E.L.); Australian Synchrotron, Clayton, Victoria 3168, Australia (M.D.d.J., D.J.P., D.L.H., C.J.G., S.J., P.K., B.J.); a...
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ورودعنوان ژورنال:
- Plant physiology
دوره 163 1 شماره
صفحات -
تاریخ انتشار 2013