[Objective]Selenium(Se)is an essential element. About1 billion people the world over suffer Se deficiency,which may lead to a series of human health disorders. The purpose of this study was to explore pathways of Se transporting to grains at the milking stage of two varieties of rice,Xiushui 48 and S. Andrea,relative to form of Se fed to the crop and to better understand mechanism of the translocation of Se to grains of the plant,so as to improve Se content in rice and breed Se-enriched rice cultivars.[Method]Two cultivars of rice(Oryza sativa L.),Xiushui 48,an Se-enriched cultivar,and S. Andrea,a general one,turn out grains differing sharply or by 3 times in Se content. They were selected for comparison in Se accumulation in grains at the milking stage. Four different species of Se[Selenite,Selenate, Selenomethionine(SeMet)and Se-methyl-selenocysteine(SeMeSeCys)]were supplied,separately, to excised panicles via stems subjected to girdling or none and flag leaves of intact rice plants of the two cultivars during the milking stage. [Result]Results show that organic selenium could enter into phloem and then be translocated to grains via stem,while only 30%~50% of the inorganic selenium in the phloem was remobilized and transferred into grains via stem,and the remaining transported through xylem. Sodium selenate could be transported to flag leaves via both phloem and xylem,while sodium selenite went mainly through xylem. When fed with sodium selenite or Se-methyl-selenocysteine,excised panicles with or without the stems girdled did not show much difference in Se concentration in grains between the two varieties. But when fed with sodium selenate and selenomethionine,excised panicles of Xiushui 48 with no stem girdled were much higher in grain Se accumulation capacity than those of S. Andrea,and not much difference was found between the excised panicles of the two varieties with stem girdled. It was also found that Xiushui 48 was more capable than S. Andrea of transporting selenate and selenomethionine from stem to grain. Obviously the former is capable of moving more Se from stem and flag leaf to grain than the latter is,which is probably the direct cause of higher Se concentration in grains of Xiushui 48. The finding also indicates that Xiushui 48 is much more capable(p = 0.05)than S. Andrea of transporting Se-Met and selenate through phloem from stems to grains,and from flag leaves to grains,too. [Conclusion]Selenium-enriched Xiushui 48 can transport more Se from stems and flag leaves to grains than Non-Se-enriched variety,S. Andrea,which is probably the direct cause of the difference between the varieties of rice in grain selenium content.%硒是人体必需微量元素,提高水稻籽粒硒含量对改善人体膳食硒营养有重要意义.以富硒水稻品种(Oryza sativa L.)秀水48和非富硒品种S.Andrea为材料,在灌浆期分别供应离体穗亚硒酸盐、硒酸盐、硒代蛋氨酸(SeMet)和硒甲基硒代半胱氨酸(SeMeSeCys),探讨两品种水稻在灌浆期向籽粒转运不同形态硒的品种差异及转运途径.结果表明:水稻体内有机硒主要通过韧皮部转运至籽粒,硒酸钠可能通过木质部和韧皮部共同转运至剑叶,而亚硒酸钠主要通过木质部转运至剑叶.秀水48从茎至籽粒转运硒酸盐和硒代蛋氨酸能力显著强于S.Andrea,并且富硒水稻秀水48从剑叶至籽粒转运有机硒(硒代蛋氨酸)能力显著高于S.Andrea.与非富硒水稻相比较,富硒水稻能通过茎和剑叶向籽粒转运较多的硒,这可能是引起水稻籽粒硒含量差异的直接原因.
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