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Grain Accumulation of Selenium Species in Rice (Oryza sativa L.)
Citation:
Carey, A., K. G. SCHECKEL, E. Lombi, M. Newville, Y. Choi, G. J. Norton, A. H. Price, AND A. A. Meharg. Grain Accumulation of Selenium Species in Rice (Oryza sativa L.). ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, 46(10):5557-5564, (2012).
Impact/Purpose:
This study, investigated the differential efficiency with which important Se species are translocated and spatially unloaded into the grain together with the comparative contributions of phloem and xylem transport.
Description:
Selenium (Se) is an essential micronutrient in which up to 1 billion people worldwide are deficient, causing a range of health disorders and potentially an increased risk of certain cancers. Consequently, there is much interest in Se biofortification of rice, the staple food for over half the world's population. This study investigated the differential efficiency with which key Se species are translocated from the rice shoot into the filling grain, and the relative contributions of phloem and xylem in this translocation, together with the spatial unloading of Se species into the grain. Total Se concentrations in rice grain samples were quantified by inductively coupled plasma-mass spectroscopy (ICP-MS) and the spatial unloading of Se into the fresh filling grain was examined by synchrotron X-ray fluorescence (SXRF) microtomography. The results demonstrate that organic species, selenomethionine (SeMet) and selenomethylcysteine, SeMeSeCys, are transported to the rice grain far more efficiently than inorganic species, selenite and selenate. SeMet and SeMeSeCys are translocated via the phloem, while xylem transport plays a role in the shoot-to-grain translocation of inorganic Se. The spatial unloading of Se was markedly different for selenite, SeMet and SeMeSeCys fed grain, with both organic species rapidly dispersing through the pericarp/aleurone layer, and into the endosperm, and SeMeSeCys also showing significant accumulation in the embryo, while selenite was retained at the point of grain entry, the ovular vascular trace.
