Effects Of Different Concentration Of Exogenetic Selenite And Selenate On Selenium Uptake, Distribution And Translocation Of Winter Wheat

It is estimated that between 500 and 1000 million people worldwide may be deficient in Se. Growing plants enriched with selenium could be an effective and safe way to reduce dietary deficiencies and increase health benefits. Wheat is the second important crop in China, and it is also a staple food crop for northern people. Therefore, there is a significant impotance for study of increasing selenium content in wheat grain.In this thesis, a pot experiment was carried out to investigate the uptake, accumulation, distribution and translocation of selenium(Se4+ & Se6+) in winter wheat, the main food crop in north China., and elucidate the phenomenon from the aspects of plant physiology and transformation of soil selenium fractionation. In addition, a field experiments was conducted to research accumulation of selenium in six main varieties of winter wheat in north China, and wheat was sprayed with selenium(Se4+ & Se6+)solution at different growth periods. The aim was to provide database for rational supplement selenium in the main wheat-producing areas in China. The results was described as below:1. At seeding stage, wheat height and biomass was significantly lower in the selenium treated soil than that without added selenium. However, at the late growth periods, wheat height and biomass first increased with the increase of soil selenium concentration, and then decreased. The tolerance to selenium improved with the wheat growth. The 10% effective concentration(EC10) of wheat in selenate and selenate treated soil increased from 1.42 and 0.28 mg/kg at seeding stage to 28.48 and 4.56 mg/kg at harvest time, respectively. The stimulated(≤1 mg/kg) or inhibited (≥2.5 mg/kg) effect of selenate on wheat height and biomass was significantly greater than that of selenite. Wheat seed yield increased with the increase of soil selenite-Se and selenate-Se concentration, and peak at 2.5 mg/kg(selenite) and 1mg/kg(selenate). Physiological metabolism analysis of winter wheat leaves showed that lower concentration of selenium in soil (Se (Ⅳ)≤5mg/kg and Se (Ⅳ)≤0.5mg/kg) stimulated the activity of GSH and POD, and decreased MDA (Se≤2.5mg/kg) contents significantly. However, high concentration of selenium induced the produce of lipid peroxides, and the content of MDA increased.2. Added selenium increased the biomass of various wheat organs in all tested selenite levels and≤2.5 mg/kg selenate treatment, while it decreased the biomass when selenate concentration was more than 2.5 mg/kg. Among various wheat organs, leaves and roots was affected greatest by exogenetic selenite and selenate. Contents of selenium in wheat organs varied in the following order: root > seed > leaf >wheat straw > glume in selenite treatment, while it was leaf > seed > glume > wheat straw > root in the selenate treatment. More selenium was transported from root to the aerial parts in selenate treatment than selenite treatment. However, the transported selenium mainly accumulated in the leaf in selenate treatment, while it could easily be assimilated and entered the seed. Transport factor further indicated this view.3. Soil selenium concentration increased more slowly with the increase of exogenetic selenium in the selenate treatment than that in the selenite treatment. Non-rhizosphere soil had more selenium than rhizosphere soil in selenate treatment, while the opposite was in the selenite treatment. Selenium concentration of various fractionation increased significantly with the increase of exogenetic selenium(P<0.05). Exchangeable selenium, selenium bound to carbonate and iron and manganese oxides bound selenium were the main selenium fractionation in selenite treatment, while it mainly was residual selenium in selenate treatment. concentration of soluble selenium was lower than 10% both in selenite and selenate treatment. contents of selenium in wheats had significantly correlation with the soil selenium fractionation except for residual form(P<0.05).4. Field experiment showed that wheat genotype had significantly effect on the wheat yield and harvest index. Particularly, the yield and harvest index of XN-979 and XN-889 were higher than the other wheat varieties. Spraying selenium at jointing stage increased wheat yield more than spraying selenium at filling stage. Contents of nitrogen, phosphorus and potassium in wheat varied greatly in different wheat varieties. Spraying selenate solution increased contents of nitrogen and phosphorus in wheat seed, but decreased the content of potassium. Selenium contents in different wheat varieties had significant difference. XN-889 and YF-175 accumulated more selenium than the other wheat varieties, and wheat accumulated more selenium when spraying selenium at filling stage than spraying selenium at jointing stage.