The Se Content And Speciation Of Selenium In Se-enriched And Se-free Rice Different Parts Treated By Foliar Sodium Selenite

Selenium(Se)is an essential trace element for humans.About 70% of the regions in China face Se deficiency problems.Selenium enriched rice(Oryza sativa L.)has been increasingly seen in the daily life.Spraying Se fertilizer on the leaves is a commonly used method to enrich Se in rice.The study aims to research the grain in white rice with the same selenium content in brown red rice provided with the different concentrations of sodium selenite in the Se-free white rice using pot experiment,Under the similar total selenium contents,we research on the organic selenium and inorganic selenium content in different parts of the grain by atomic fluorescence and found the following results:1.In the same soil environment,the ability to absorb and transfer Se in the root of Se-enriched rice was stronger than Se-free rice,while the Se content in the leaves and seeds were significantly higher than Se-free rice.The leaves of Se-free rice can absorb and transport Se,but due to the difference of roots sensitivity to selenium,the content of Se in grain is low,that is one of the main reason for the difference of Se in grains between Se-free and Se-enriched rice.2.After the application of sodium selenite to Se-free rice,the concentration of total Se increased significantly and the proportion of organic Se decreased from the embryo to the glume in grains.Under the treatment of 12.5mg/L concentration,the concentration of total Se in brown rice reached to 0.083 mg/kg(II You838)and 0.070 mg/kg(Gang You725),which increased by 5.9 and 8.1 times compared with the untreated group,exceeding the national Se standard for rice 0.04mg/kg.However,nearly half of the Se in brown rice was stored in bran as inorganic Se,while in embryo and endosperm the remaining Se found as organic Se.3.The optimum concentration of Se in 725 and 838 white rice was obtained through the organic Se content proportion in brown and polished rice.The optimum concentration for brown rice was 5mg/L and 10 mg/L in 725 and 838 respectively,and that of polished rice was 10mg/L for both of materials.4.The optimum concentration obtained by the trend of organic selenium was lower than trend of total selenium content.Therefore,in the process of production of Se-rich rice,determination of organic selenium in brown rice and endosperm is more important than total selenium content.5.When total selenium contents of brown rice achieved similar trend in Se-free and Se-rich rice.The ratio of organic selenium to brown rice in Se enriched rice was 74-76%,which was much higher than that of Se-free rice viz;39-52%.The percent of organic selenium in endosperm of Se-free rice was not very different from that of selenium enriched rice.But the content of organic selenium was much lower in Se-free rice.In rice bran,80% selenium exists in the form of inorganic selenium in white rice while the proportion of organic selenium in selenium enriched red rice reached over 71%.6.In the process of producing Se-rich rice,it is better to choose Se-enriched rice,which is not only safer for human body,but also friendly to environment,and can also improve the value of by-products.In the process of selenization,Se-free rice selected for selenite foliar treatment,it is necessary to select the varieties whose leaves should be sensitive to Se and concentration of exogenous Se should be kept under keen observation.