Effects Of Application Zinc Oxid Nanoparticles On Winter Wheat Zinc Nutrition And Grain Quality

Zinc deficiency in the main food crops of Loess Plateau seriously affects the healthy survival of the people in the region,so it is very important to carry out the necessary measures to increase zinc（Zn）.The field experiment,including control（CK）,soil-applied ZnSO₄?7H₂O（SZn）,foliar-applied ZnSO₄?7H₂O（FZn）,soil-and foliar-applied ZnSO₄?7H₂O（SFZn）,soil-applied ZnO nanoparticles（SZnO）,foliar-applied ZnO nanoparticles（FZn O）,soil-and foliar-applied ZnO nanoparticles（SFZnO）,was conducted over two years to investigate the improvement of ZnO nanoparticles（ZnO NPs）on winter wheat Zn nutrition and grain quality.Meanwhile,the Zn speciation and distribution within wheat grain were also determined by using synchrotron-based X-ray absorption spectroscopy（XAS）and X-ray fluorescence microscopy（μ-XRF）.The results can be used to find a kind of more efficient and more environmental friendly Zn fertilizer for Loess Plateau,and to contribute to the improvement of Zn nutrition in Loess Plateau or around the world.The main findings are as follows:（1）Two-year field experiments both showed that all Zn treatments（including traditional ZnSO₄?7H₂O and ZnO NPs）had no significant effects on the biomass of winter wheat aboveground tissues,the harvest index of grain and the three yield factors.However,compared with no difference in agronomic indicators,the application of ZnO NPs significantly increased the Zn concentration and Zn content in the aboveground parts of winter wheat,and was significantly superior to the traditional ZnSO₄?7H₂O fertilizer,especially for the alone foliar-applied ZnO NPs（FZnO）and soil-and foliar-applied ZnO NPs（SFZnO）.However,while considering the index of grain Zn biofortification,grain Zn utilization efficiency and total Zn utilization efficiency,the treatment of FZnO(the three indicators were 8.6 mg?kg^-1,4.9%and30.4%,respectively)was significantly better than the latter(the three indicators were 0.13mg?kg^-1,0.09%and 0.45%,respectively).（2）Through experiments,it was found that whether the application of Zn or not,and whether it is the application of traditional ZnSO₄?7H₂O fertilizer or nano-fertilizer（ZnO NPs）,the Zn within the final mature wheat grain is mainly distributed in the aleurone layer and crease region.However,as expected on the results of bulk measurements,the Zn concentration in these tissues differed among treatments,being highest for foliar-applied ZnO NPs,followed by foliar-applied ZnSO₄?7H₂O and lowest in the control.At the same time,through further observations and analysis,it was found that the application of ZnO NPs also played a role within increasing the Zn concentration of the endosperm.Furthemore,the results of synchrotron-based X-ray absorption spectroscopy（XAS）showed that all three treatments presented similar spectra in appearance,and Zn in the wheat grain was mainly present as Zn phosphate,with the foliar-applied Zn compounds not effecting the Zn speciation,in despite of the form in which Zn was applied.（3）Finally,the analysis of wheat grain quality also showed that foliar application of ZnO NPs did not significantly affect the concentration of starch,total soluble sugar,protein and its components within the grains.In summary,although the Zn concentration in the endosperm of the grain only increases slightly and most of the seed coat,embryo and aleurone layer are lost during the wheat milling process,the endosperm and crease tissues look through the whole wheat grain.So,foliar-applied ZnO NPs will greatly increase Zn content in flour and improve human Zn intake.The average increment of Zn concentration(10 mg?kg^-1)has a measurable biological influence on human health.Meanwhile,in combination with the safety assessment of grain,we believe that this move will make a tremendous contribution to improving human Zn deficiency.ZnO NPs is a new Zn fertilizer worthy of promotion.