Interaction Effect Of Nitrogen And Selenium On Winter Wheat Under Two Selenium Application Modes

Nitrogen（N） is an essential element for plant growth,and the application of nitrogen fertilizer directly affects the growth of crops.Nitrogen is an important component of protein,amino acid and other organic compounds.Selenium（Se） is a necessary beneficial element for human body and animals.Selenium plays an important role in anti-oxidation and anti-bacteria,and lack of selenium can cause various diseases.The human body mainly obtains beneficial organic selenium from food,but selenium cannot be absorbed and transformed by the human body in the environment,so it is imperative to supplement selenium through crops.Most of the previous studies focused on the interaction between phosphorus and selenium,while there was a lack of systematic reports on the relationship between nitrogen and selenium.The interaction effects of nitrogen and selenium on yield and nutritional quality,antioxidant system and Se subcellular distribution and morphology of winter wheat were studied by pot,hydroponic and field experiments.The main conclusions are as follows:1.The yield of winter wheat in field was increased by nitrogen application under both selenium application methods,and the yield of winter wheat was increased more significantly at the lower level（90kg/hm²）and moderate level（180 kg/hm²）.In addition,the yield of winter wheat was significantly increased by selenium spraying,which was better than that of root application.Under pot condition,the yield of winter wheat could be increased by both Se application methods,and the increase of winter wheat yield was greater by medium N application level（200 mg/kg）.Compared with Se spraying,Se application could significantly increase the yield of potted winter wheat.Under hydroponic condition,the dry matter weight of winter wheat under N_7.5 level was decreased by high concentration Se application（5μmol/L root application or 50 mg/L spray application）.N_7.5 treatment also reduced dry matter weight of winter wheat at high Se level.However,when selenium application concentration was low（1 μmol/L）,the dry matter weight of winter wheat was increased by root selenium application,and the increase range of N_7.5 application level was greater.2.The absorption of P,K,B,cu,Mn and Zn of winter wheat increased significantly of both Se application methods at the medium（200 mg/kg）N level,but the absorption of Mo was decreased,and root Se application was better than Se spraying.The calcium absorption of winter wheat was promoted by root application of Se and decreased by spraying Se.At the low nitrogen level（100 mg/kg）,root selenium application promoted the absorption of magnesium in winter wheat,and selenium spraying increased the absorption of magnesium in winter wheat at the high nitrogen level（400 mg/kg）.Grain of selenium and nitrogen were significantly positive correlation,selenium and molybdenum has significant negative correlation relationship,nitrogen and potassium,magnesium and boron,copper,iron has significant positive correlation,magnesium and copper were significantly positive correlation,the grain of the boron and molybdenum has significant negative correlation relationship,Straw and leaves of selenium and phosphorus and potassium was significantly positive correlation,selenium and boron was significantly negative relationship,There was a significant positive correlation between nitrogen and calcium,magnesium,copper and iron;there was a significant positive correlation between selenium in glume and nitrogen and potassium;there was a significant negative correlation between selenium and boron;there was a significant positive correlation between nitrogen and potassium,copper and iron;there was a significant negative correlation between selenium and iron in roots;there was a significant positive correlation between nitrogen and calcium.3.Under the same nitrogen level,increasing selenium application concentration could reduce the root length of winter wheat,but increasing selenium spraying concentration could increase the root length,reduce root surface area and root volume;The root length,total root volume and root surface area could be increased by increasing nitrogen application level under Se spraying condition.The total root volume and root surface area decreased with the increase of nitrogen application level.The net photosynthetic rate,stomatal conductance and transpiration rate could be increased by increasing nitrogen application level under two selenium application methods.Increasing Se concentration reduced the net photosynthetic rate,stomatal conductance and transpiration rate of winter wheat at N_0.5 level,decreased the net photosynthetic rate of winter wheat at N_7.5 level,but increased the stomatal conductance and transpiration rate of winter wheat at N_7.5 level.The net photosynthetic rate,stomatal conductance,intercellular carbon dioxide concentration and transpiration rate of winter wheat were significantly increased with the increase of nitrogen application level under Se spraying condition.Under the same nitrogen application level,the stomatal conductance of winter wheat could be increased by the two Se application methods,and the transpiration rate of winter wheat under Se application was higher than that under Se spraying.4.Under the two selenium application methods,nitrogen application could increase the nitrogen and selenium contents in different parts of winter wheat,and the low（90 kg/hm²）or medium（180 kg/hm²）nitrogen application level increased the nitrogen and selenium contents of winter wheat more significantly.Selenium spraying could significantly increase the selenium content in different parts of winter wheat and nitrogen content in glume,Straw and leaves,while selenium application can increase selenium content in various parts of winter wheat in field,and selenium spraying is superior to selenium application.The two selenium application methods can increase the grain selenium content of potted winter wheat,and the moderate（200 mg/kg）can increase the nitrogen content and selenium content of winter wheat more significantly,and selenium application is better than selenium spraying.Under Se application condition,N_7.5 treatment promoted Se accumulation in shoots of hydroponic winter wheat,but inhibited Se accumulation in roots.At the low nitrogen level(N_0.5),spraying high concentration selenium（100 mg/L）promoted the absorption of nitrogen in winter wheat.Under the medium(N_7.5)nitrogen application level,the two selenium application methods inhibited the accumulation of nitrogen in above ground and root of hydroponic winter wheat,and significantly increased the selenium content in above ground of winter wheat,and the moderate(N_7.5)nitrogen application level increased the selenium content more significantly.However,high concentration(N₁₅)nitrogen application significantly reduced selenium content in underground part of winter wheat.The effect of root selenium application was better than that of selenium spraying at medium nitrogen level.5.Under the root selenium application condition,increasing the nitrogen application concentration could decrease the soluble partial selenium content of the shoot of winter wheat,and increase the soluble partial selenium content in the underground of winter wheat;Under Se spraying condition,with the increase of N concentration,the soluble partial se content in above ground and underground parts of winter wheat decreased firstly and then increased.The selenium content of organelles in shoot and shoot of winter wheat was decreased by increasing nitrogen concentration under root selenium application.Under the Se spraying condition,increasing N concentration increased the selenium content of winter wheat shoot organelles,and with the increase of N concentration,the content of winter wheat subcellular organelles first increased and then decreased,and reached the highest value under N_7.5 treatment.Under the same nitrogen application level,the content of selenium in winter wheat organelles under root application was higher than that of under selenium spraying.Under the same nitrogen application level,the selenium content in cell wall of winter wheat treated with root selenium was higher than that of selenium spraying.Under the root Se application condition,the effect of increasing N application level on selenocysteine in underground part of winter wheat increased firstly and then decreased,and it was the highest at N_7.5.Under Se spraying,N₁₅ significantly increased the content of selenocysteine in subsurface of winter wheat,and with the increase of N application level,the selenocysteine content in subsurface of winter wheat increased firstly and then decreased,and it was the highest in N_7.5.Under the selenium application condition,the Se⁴⁺ content in the above-ground part of winter wheat was the lowest in N_7.5,the highest in N₁₅,and the highest in the underground part of winter wheat in N_7.5.Under Se spraying,increasing N level increased Se⁴⁺ content in shoot and root of winter wheat.The methionine content in shoot and root of winter wheat increased firstly and then decreased with the increase of nitrogen application level under the root selenium application condition,and reached the highest value in N_7.5.The methionine content in shoot and root of winter wheat increased with the increase of nitrogen application level,and reached the maximum value at N₁₅.The contents of Fe-Se,FW-Se,Fnac L-Se,FHAc-Se,FHCl-Se and FC-Se in shoot of winter wheat were significantly decreased by increasing nitrogen application level under root Se application.Under Se spraying condition,the content of Fe-Se and Fnac L-Se in winter wheat shoot under N_7.5 treatment was significantly higher than that under N_0.5 and N₁₅ treatment,but N_7.5 treatment reduced the content of FC-Se in winter wheat shoot.At the N_0.5 level,the contents of Fe-Se,FW-Se,Fnac L-Se,FHAc-Se and FHCl-Se in winter wheat under root selenium application were higher than those under selenium spraying,while at the N_7.5 level,the contents of FW-Se,FHAc-Se and FHCl-Se in winter wheat under root selenium application were higher than those under selenium spraying.6.Under the same nitrogen application level,root selenium application decreased the content of MDA in overground and increased the content of MDA in underground parts of winter wheat.Selenium spraying decreased MDA content in overshooting of winter wheat,but had no significant effect on underground.Under the condition of low root selenium application,increasing nitrogen application level significantly increased MDA content in winter wheat shoots,while under the condition of high root selenium application,increasing nitrogen application level significantly increased MDA content in winter wheat shoots.At the level of N_0.5,increasing selenium application level under the two selenium application modes reduced ASA content in shoot of winter wheat.At N_7.5 level,increasing Se application level increased ASA content in shoot of winter wheat.Under the two selenium application methods,increasing nitrogen application level increased ASA content in winter wheat underground,and the increase of ASA content in winter wheat overground was greater at medium(N_7.5)nitrogen application level.Under the two selenium application methods,increasing nitrogen application level decreased the content of GSH in overground and increased the content of GSH in underground of winter wheat.Under the same nitrogen application level,increasing selenium application level decreased the content of GSH in winter wheat.Under the same root selenium application level,increasing nitrogen application level could increase CAT content in underground part of winter wheat.The content of CAT in shoot of winter wheat was decreased by increasing N concentration and Se level.Under the same Se application method,increasing Se application level could increase CAT content in underground part of winter wheat.The content of CAT in shoot of winter wheat was increased by Se application in root and Se spraying.The CAT content of winter wheat treated with root selenium was higher than that treated with selenium spraying.Under the two selenium application methods,the content of APX in winter wheat aboveground decreased with the increase of selenium application level,while the content of APX increased with the increase of nitrogen application level.The activities of POD and SOD in shoot of winter wheat were significantly increased by increasing nitrogen application level under low root selenium application.Under the low concentration Se spraying condition,increasing N application level significantly increased POD activity in winter wheat shoot,and significantly decreased SOD activity in winter wheat shoot and shoot.The POD activity of winter wheat was significantly increased and SOD activity was significantly decreased by spraying high concentration Se at the same nitrogen level.