Effects Of The Level And Frequency Of Foliar Spraying Of Selenium At Different Time Points On Selenium Concentration In Different Parts Of Wheat Plants

Selenium（Se）is an essential trace element for the human body.It forms the active site of glutathione peroxidase in the form of selenocysteine and plays an antioxidant role.Plant foods are the primary source of Se for humans.Wheat is the staple food crop in the north of China.Improving the Se concentration of wheat grains is of great significance in increasing human Se intake.The foliar spraying of Se at the grain filling stage of wheat is beneficial to transporting Se to the grain.However,it is unclear whether spraying at the specific time point after the beginning of grain filling is beneficial to improving the utilization efficiency of Se.In this study,four foliar Se spraying levels and two Se spraying forms（selenate and selenite）were performed in the field.0 g·hm^-2（Ⅰ）,37.8 g·hm^-2（Ⅱ）,and 56.7 g·hm^-2（Ⅲ）（calculated as pure Se）,the foliar sprayed Se concentrations were 0（CK）,28 mg·L^-1（Ⅰ）,56 mg·L^-1（II）,and 84mg·L^-1（III）,respectively.They were spraying once on the 2nd,9 th,and 16th day after the start of grain filling and spraying two times continuously on the 2nd and 9th day,the 2nd day and the 16th day,the 9th day,and the 16th day after the start of the grain filling.Then samples were collected on the 7th day after Se spraying and when the grains were mature to determine the Se concentration of different parts of the wheat plant and to analyze the effects of Se spraying form,Se spraying concentration,Se spraying time point,and Se spraying times on different parts of the plant,especially the grain Se concentration.The main results are as follows:（1）After spraying different concentrations of selenium and selenium salt during wheat grouting,the content of wheat flags,leaf sheaths,cobs,nodes,internodes,roots,glume,especially seeds,selenium High（P<0.05）.With the improvement of selenium concentration,different parts of wheat plants can maintain a large concentration difference.The leaves can transfer selenium more to the roots,glume,and grains through leaf sheath,cobs,nodes,and internodes to increase their selenium concentration.（2）After 7 days and 14 days after the start of the wheat grouting,after 7 days and14 days after the selenium and sub-selenium salt,the selenium content of flag leaves,leaf sheaths,cobs,nodes,internodes,roots,glume and grains is decrease delayed with the sampling time.Except for glume and grains,the flag leaves,leaf sheaths,cobs,nodes,internodes,and root selenium contents of 7 days after grouting after the beginning of the grouting.The selenium content on the 14th day after spraying on the second day,but the selenium content on 7 days after the 2nd day after the start of the grouting,indicating that the selenium spraying on the 9th day after the beginning of the grouting can maintain the wheat flag leaves and leaf sheaths to maintain comparison,high selenium level.（3）Regardless of the selenic acid or sub-selenium,two consecutive times of spraying for wheat flags,leaf sheaths,cobs,nodes,and internodes,roots,and glume,especially the selenium content of seed grains is significantly higher than that of spray one time（P<0.05）,and the two spraying time should be selected at the beginning and the middle stage of the grouting period..（4）At the same level of selenium,the selenium concentration of wheat flags,leaf sheaths,cobs,nodes,and internodes,roots,glume and grains after spraying selenium is significantly higher than that sprayed selenium（P<0.05）.