Research Of Selenium Enrichment Characteristic And Speciation Distribution In Sweet Potato

After selenium has been established as an essential trace element in the human body,its influence on human biological functions has been studied in depth.Since the human body cannot synthesize selenium itself,it is particularly important to obtain selenium from food to meet daily needs.Therefore,the rational use of crops to enrich selenium is the focus of current research.Sweet potato,also known as sweet potato,sweet potato,etc.,is an annual herbaceous plant of the family Convolvulaceae.It is one of the favorite foods for people in winter.It is rich in various trace elements,amino acids,proteins,polysaccharides and other components,with enhanced immunity,anti-oxidation,anti-tumor and other effects.In this project,sweet potato was used as the experimental material,and field experiments were conducted to study the physiological characteristics of sweet potato,selenium-enriched regularity of various parts of sweet potato,and selenium absorption and transport of sweet potato under different selenium fertilization concentrations.The effects of long-term application of selenium in soil,application of selenium on soluble protein,crude polysaccharide,selenoprotein,selenium polysaccharide,and mineral elements in sweet potato roots,and high-performance liquid chromatography/mass spectrometry for selenium methyl selenohalide in sweet potato roots Cysteine,selenomethionine,and selenocystine were used for qualitative and quantitative analysis.The following conclusions have been reached:?1?The tolerance of sweet potato to selenium application on foliar surfaces was higher than that of selenium application in soil.Selenium seedlings appeared when soil selenium concentration was ?2mg/L,but no selenium seedlings appeared in the whole selenium concentration range.There were only yellowing symptoms in 6,8 and10mg/L gradients.Therefore,selenium-enriched sweet potato should be planted with foliar fertilizers.In the application of selenium gradient in the range of 0.4-10mg/L,no matter which method of application of selenium,sweet potato leaves chlorophyll content compared with the control group showed a gradually decreasing trend.It was demonstrated that selenium had inhibitory effect on chlorophyll content in this gradient;in the range of 0.4-10 mg/L selenium applied,applying selenium to the foliage promoted the net photosynthetic rate of sweet potato.The application of selenium in soil showed the characteristics of first increase and then decrease,reaching the maximum at 0.8 mg/L;the application of exogenous selenium had no effect on the apparent characteristics of sweet potato;under both selenium application methods,the yield of sweet potato was affected by selenium application.Gradient increases first and then decreases,reaching a maximum at 0.8 mg/L.The optimum selenium concentration of net photosynthetic rate and yield under the conditions of soil application of selenium was 0.8 mg/L.?2?The selenium content of sweet potato roots increased with the increase of selenium concentration in the whole application of selenium in soil.The stems and leaves showed the characteristics of first increase and then decrease,and the selenium content of all parts was higher than the control group.The selenium content of sweet potato tuber reached the maximum value of 1.05 mg/kg when the selenium fertilizer concentration was 2 mg/kg,which was 36 times that of the control group.The selenium content of the stem and leaf reached the maximum value of 1.61 when the selenium fertilizer concentration was 1.6 mg/kg.2.22 mg/kg was 55 and 77 times that of the control group.In the first year of selenium application,the soil was continuously planted for two years.The regularity of selenium in sweet potato was the same as in the first year and higher than that in the control group.In the second year,the highest selenium content in roots,stems and leaves of sweet potato was 0.72,1.37,and 1.96 mg/kg,which was 22,48,and 67 times higher than that of the control group.The lowest ones were:0.30,0.46,and 0.87 mg/kg.10,16,and 30 times.In the third year,the highest selenium content in roots,stems and leaves of sweet potato was 0.63,1.11,and 1.72 mg/kg,which was 21,38,and 59 times higher than that in the control group.The lowest values??were 0.04,0.36,and 0.50 mg/kg in the control group.1.3,12.5,17 times.After the soil was planted in the third year,the highest value of selenium in soil could reach 2.9mg/kg.The lowest value of 0.43mg/kg was 10.8 and1.6 times that of the control group,indicating that the soil still had selenium-enriched abilityin the fourth year.Selenium applied on foliar surface The selenium content of sweet potato tuber increased with the increase of selenium concentration in the whole selenium concentration.The stems and leaves showed the characteristics of first increase and decrease,and the selenium content of all parts was higher than that of the control group.The selenium content of roots reached a maximum value of 4.28 mg/kg at a concentration of 10 mg/kg of selenium for the control group,148 times for the control group,and the maximum of 12.98 mg/kg for the selenium content at a concentration of selenium of 8 mg/kg was the control group.At 36 times,the leaf reached a maximum of 30.90 mg/kg at a selenium concentration of 2 mg/kg,which was 71times that of the control group.Foliar application of selenium was stronger than soil application of selenium.The selenium content of leaves under selenium application was 2.0,3.5,4.0,4.0,and 3.8 times higher than that of selenium applied to the soil.The selenium content of stems was 8.5,8.5,8.0,7.1,and 8.5 times higher than that of selenium applied to the soil.16.1,12.0,10.5,24.0 times.Under the two selenium application methods,the selenium content of sweet potato showed the characteristics of leaf>stem>tube root.Under the two selenium application methods,the absorption coefficient gradually decreases with increasing gradient of selenium.Under the conditions of soil application of selenium,the transport coefficient gradually decreased,and selenium applied on the leaves increased gradually.From the side,selenium was more likely to be concentrated in the roots of the trees with the increase of selenium concentration.?3?Only the Na,Mg,and K of sweet potato were higher than the soil background value,and the other 11 species were lower than the soil background value;the application of selenium only affected the content of Na,Mg,P,and K.The difference in the content of mineral elements in the two selenium application modes is0.003-1.5ug/kg,so the difference is negligible;the overall trend of Na,K,Fe and the control group shows an increasing trend;the content of Mg,Ca and Mn The overall trend is to decrease first;the P and B contents show a decreasing trend as the gradient of selenium application increases;Si,Ni,Co,Zn,and Cu have little effect on the selenium and concentration of selenium,and their contents remain basically unchanged.?4?The response surface methodology was used to optimize the conditions for extraction of soluble protein and crude polysaccharide from sweet potato roots.The optimal conditions for extracting soluble protein were as follows:0.9%sodium chloride solution,solid-liquid ratio 1:25,temperature 40°C,and time 90 min.The soluble protein content was 73.84 mg/L.The optimum conditions for extracting crude polysaccharides were as follows:ratio of material to liquid 1:25,temperature 75°C,time 100 min.Three groups of parallel experiments were performed with blank groups.The mean polysaccharide content was 52.89 mg/mL and the relative error was2.7%.There was no significant difference.Both selenium application methods can effectively increase the content of sweet potato root protein and polysaccharide.Selenium in protein and polysaccharide reached the highest value of 0.055mg/kg and 0.040mg/kg at 2mg/kg under the condition of soil application of selenium,and the lowest value of 0.017mg/kg and0.028mg/kg at 0.4mg/kg was the control.The group's 1.49,1.17 times.Selenium content in protein and polysaccharide was 0.035 mg/kg and 0.025 mg/kg was 3.27,1.07 times that of the control group when selenium concentration was 0.2 mg/kg under the condition of selenium applied on the foliar surface.The selenium content in the protein and polysaccharide was the same.The maximum values??reached at 10mg/kg were 0.47 and 0.42 mg/kg,respectively,which were 42.7 and 18.2 times that of the control group.The selenium content in polysaccharides was increased with the application of selenium in the soil,while the selenium content was increased with the high concentration of selenium.The selenium content in the protein was improved with the application of selenium.In terms of the overall trend,the organic selenium in the sweet potato roots tends to exist as selenium in the protein.The absorption of selenium by sweet potato was larger at 1.4 mg/kg².5 mg/kg,and within this range,selenium had better effect on the increase of root protein and polysaccharide content of sweet potato than other concentrations.Regardless of the application of selenium on the foliar surface or application of selenium in the soil,the contents of the five soluble selenium were:NaoH>Tris-HcL?NacL>H₂O>HcL,and the content increased with the increase of selenium concentration.Under the conditions of soil application of selenium,the selenium content of total selenium content leached by NaoH,Tris-HcL,NacL,H₂O,HcL up to 81%,72%,70%,67%,59%.Under the condition of selenium applied on the foliar surface,the selenium content of total selenium content leached by NaoH,Tris-HcL,NacL,H₂O,and HcL was up to 91%,82%,68%,63%,and 59%.?5?Se-Cys₂ accounted for 0.036%of the total mass of sweet potato,Se-MeSeCys 0.39%,Se-Met 0.44%,sweet potato organic selenium?0.866%,Se-Cys₂under selenium conditions.The content accounted for 0.051%of the total mass of sweet potato,0.38%Se-MeSeCys content,0.41%Se-Met content,and organic selenium content of sweet potato?0.831%.Three amino acid contents:Se-Met>Se-MeSeCys>Se-Cys₂.Se-MeSeCys and Se-Met have higher selenium content than foliar application under conditions of selenium application in soil.However,selenium content in Se-Cys₂ at the 0.4 mg/kg soil level was higher than that at the foliar surface.Selenium at the other surface was higher than that at the other soil level.The selenium content in Se-MeSeCys accounted for 24.94%of the total selenium in the soil under selenium application;the Se-Met selenium content accounted for25.86%of the total selenium;Se-Cys₂ selenium accounted for the largest proportion of total selenium.It is 11.5%.The content of selenium in organic selenium accounts for 62.3%of the total selenium.The selenium content in Se-MeSeCys accounted for 17.7%of the total selenium,the Se-Met selenium content accounted for 17.1%of the total selenium,and the Se-Cys₂ selenium content accounted for the largest total selenium.The proportion is9.6%.The selenium content in detectable organic selenium accounted for 44.4%of total selenium.