| Selenium is an essential nutritional element for the human body.The increase in the content of selenium in agricultural products is of great significance to the improvement of human health and the prevention of specific diseases.In this project,field experiments were conducted to study the effects of exogenous selenium on the content of selenium,cadmium and other quality indicators in Watermelon(Citrullus lanatus),fructus momordicae(Siraitia grosvenorii)and Sugar orange(Citrus shatangju).The purpose was to provide a theoretical basis for the production of high-quality and efficient selenium-enriching and cadmium-reducing fruits.The main findings are as follows:1.A field experiment was applied to investigate the effects of basal application of different doses of selenium fertilizer(0.26kg/hm~2,0.51kg/hm~2,1.03kg/hm~2)or foliar spraying in different periods(flowering,fruit-setting)on the content of selenium and cadmium,and quality indicator as well as antioxidative system of watermelon,aiming to explore the optimum conditions of applying selenium to watermelon.The result showed that the selenium content of watermelon flesh was among 0.014~0.106mg/kg which reached the Hubei se-rich standard for fruits and vegetables(>0.01mg/kg).All selenium fertilizer treatments increased the selenium content in the flesh.Compared with CK,the application of selenium fertilizer at the base increased flesh selenium content by63%~282%and the spraying during the flowering stages increased by 9%.The selenium content of flesh was the highest of all treatment when 0.26kg/hm~2 selenium fertilizer was applied at the base.The application of selenium fertilizer also significantly increased the content of soluble sugar of watermelon flesh(P<0.05),and the sugar content of spraying at the fruit setting stage was significantly higher than that of the base application and spraying at the flowering stage.The low-dose(0.26kg/hm~2,0.51kg/hm~2)selenium fertilizer at the base and the foliar application of selenium fertilizer application all improved the antioxidant capacity of the watermelon and significantly reduced the MDA content in the leaves.Considering comprehensively,the selenium application method of watermelon is 0.26kg/hm~2 sodium selenite at the base.2.The effects of basal application singly(G),basal and foliar application combied(G+Y20),and foliar application only in different concentrations(Y40+40,Y20+20,Y40)of selenium fertilizer on the content and distribution of selenium,cadmium and other nutritional elements,as well as the Vc content in Siraitia grosvenorii were studied.The results showed that the selenium in the Siraitia grosvenorii was mainly distributed in the flesh and seed,and was less distributed in the peel.The application of selenium fertilizer significantly increased the content of selenium in Siraitia grosvenorii(P<0.05),which was 1.6~21.6 times that of CK.The selenium content of G,G+Y20,Y40 met the Hubei se-rich standard for dried fruit(among 0.1~0.5mg/kg).Of all treatments,the cadmium content in Siraitia grosvenorii was under the limit of Hubei cadmium pollution for fruits and their products(0.05mg/kg).The treatment of G,G+Y20 and Y40 further reduced the content of cd in Siraitia grosvenorii(P<0.05).The application of exogenous selenium also significantly reduced the content of iron,Vc and soluble sugar in the flesh of Siraitia grosvenorii.3.The effects of basal application(G),foliar application once(Y40)and foliar application twice(Y20+20)of selenium fertilizer on the content of selenium,cadmium,iron and zinc as well as nutrional quality of the Sugar orange flesh were studied.The results showed that appling selenium fertilizer increased the selenium content in orange pulp,but the difference was not significant compared with CK(P>0.05).At the same time,the Cd content reduced by 29.6%~50.3%,compared to CK.The application of selenium had no significant effect on the content of soluble sugar and soluble solids in the flesh,but the selenium application at the base significantly increased the content of iron,Vc and titratable acidity in flesh(P<0.05). |
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