| Field experiments were conducted from 2015-2016 and 2016-2017 under standard field conditions at experimental farm of Shandong Agricultural University（36°9′ N,117°9′ E）.Two high-yield wheat varieties were used including Shannong 23 and Jimai 22.Four nitrogen（N）application treatments of 0（N0）,180（N1）,240（N2）and 300 kg·hm-2（N3）,respectively,were designed to study the effects of N application on photosynthesis characteristics and water consumption characteristics in different wheat varieties,thus providing a theoretical basis for high-yield cultivation of wheat.During the 2018-2019 and 2019-2020 wheat growing seasons,field experiments were carried out at Shiwang village wheat experimental station（35°42′N,116°41′E）,located in Xiaomeng town,Yanzhou district,Jining city,Shandong Province,China.Shiwang wheat experiment station is 60 km away from the experimental farm of Shandong Agricultural University,and the ecological conditions of these two experimental locations are the same.Three wheat varieties with different yield levels-Yanong 1212（Super-high-yield wheat variety,YN）,Jimai 22（high-yield wheat variety,JM）,and Liangxiang 99（middle-yield wheat variety,LX）-were used in super-high-yield soil fertility field（S）with yield level up to 10500 kg·hm-2 and in high-yield soil fertility field（H）with yield level up to 9000 kg·hm-2.This study was to investigate the effects of soil fertility on photosynthesis and senescence characteristics in different wheat varieties,thus providing a theoretical basis for the high-yield and high-efficiency of wheat cultivation.1 Effects of N application on photosynthesis characteristics and water consumption characteristics in different wheat varietiesWater consumption characteristics of wheat.During the two wheat growing seasons,under N2 condition,the water consumption amount from anthesis to maturity,the soil water consumption and its ration to the total crop evapotranspiration（ETc）during the whole growing season,soil water consumption in the 40-160 cm soil layer of SN variety were significantly higher than those of JM variety.Comparison among N application treatments,the water consumption amount from anthesis to maturity,the soil water consumption and its ration to the ETc during the whole growing season,soil water consumption in the 20-160 cm soil layer of SN variety decreased in the order of N2、N3>N1>N0.These results indicated that N2 treatment of SN was beneficial to promote the absorption and utilization of deep soil water storage,and save the irrigation water amount.Photosynthetic characteristics and dry matter production of wheat.During the two wheat growing seasons,under N2 condition,the total intercepted photosynthetic active radiation fraction（CaR）of wheat canopy,net photosynthetic rate（Pn）and and transpiration rate（Tr）of flag leaves during the late grain filling stage,dry matter accumulation amount at maturity,post-anthsis assimilates allocation to grain and dry matter accumulation in grain at maturity were higher in SN than in JM.Comparison among N application treatments,the total CaR of wheat canopy,the Pn and Tr of flag leaves during the late grain filling stage,the dry matter accumulation amount at different growth stages,post-anthsis assimilates allocation to grain and dry matter accumulation in grain at maturity of SN decreased in the order of N2、N3>N1>N0.These results indicated that N2 treatment of SN was beneficial to improve the light interception capability and photosynthetic ability of plant,and accelerate the photosynthetic assimilates production and its distribution to grain.Plant N accumulation,distribution and soil nitrate nitrogen content of wheat.During the two wheat growing seasons,under N2 condition,SN had higher plant N accumulation and grain N accumulation amount,and lower soil NO3--N content in the 60-180 cm soil layer at maturity,as compared to JM.Comparison among N application treatments,the plant N accumulation at different growth stages,and grain N accumulation amount at maturity of SN decreased in the order of N2、N3>N1>N0.The soil NO3--N content in the 60-160 cm soil layer at maturity of SN decreased in the order of N3>N2、N1>NO.These results indicated that N2 treatment of SN was beneficial for the improvements of plant N accumulation after anthesis and grain N accumulation,and for the reduction of NO3--N leaching.Grain yield,water and N use efficiency of wheat.During the two wheat growing seasons,under N2 condition,the grain number,1000-grain weight,grain yield,water use efficiency（WUE）,irrigation water use efficiency（IUE）and nitrogen partial factor productivity（PFPN）of SN were higher than those of JM.Comparison among N application treatments,the grain number,1000-grain weight,grain yield of SN decreased in the order of N2、N3>N1>N0.The IUE of SN decreased in the order of N2>N3>N1>N0,and the PFPN of SN decreased in the order of N1>N2>N3.These results indicated that N2 treatment of SN was the optimal treatment for yield,water and N use efficiency of wheat.2 Effects of soil fertility on photosynthesis and senescence characteristics in different wheat varietiesSoil physicochemical characteristics and microbial properties in wheat filed.The soil nutrient contents including organic matter,total N,available N,available phosphorus and available potassium in the 0-40 cm soil layer at jointing and anthesis stages were higher in super-high-yield soil fertility field（S）than in high-yield soil fertility field（H）.S had lower soil bulk density in the 0-40 cm soil layer at anthesis and maturity stages than those of H.The soil porosity and soil aggregate（>2 mm and 0.25-2 mm）distribution,soil microbial biomass N and soil microbial biomass carbon,soil enzyme activities（i.e.urease activity,invertase activity,alkaline phosphatase activity and catalase activity）in the 0-40 cm soil layer at anthesis and maturity stages decreased in the order of S>H.The results indicated that the physicochemical characteristics and microbial properties of the topsoil in S were better than in H.Photosynthetic characteristics and dry matter production of wheat.The Pn and Tr at 7,14,21,28 and 35 days after anthesis（DAA）,the leaf area index and the CaR of wheat canopy after anthesis of S were higher than those of H.S significantly increased the sucrose content and sucrose phosphate synthase activity of flag leaves during grain filling stage,dry matter accumulation amount at different growth stages,post-anthsis assimilates allocation and its contribution to grain,dry matter accumulation in grain at maturity as compared to H.The Pn and Tr of flag leaves at 14,21,28 and 35 DAA,the leaf area index and CaR of wheat canopy at 28 and 35 DAA decreased in the order of YN>JM>LX in S.The sucrose content and sucrose phosphate synthase activity of flag leaves at 14,21 and 28 DAA,the dry matter accumulation amount at maturity stages,post-anthsis assimilates allocation to grain,dry matter accumulation in grain at maturity were higher in YN than in JM and LX.These results indicated that YN planting in S was beneficial to enhance the photosynthetic capacity and light interception capability of leaves,and increased the accumulation of dry matter and its distribution to grain post-anthesis.Plant N accumulation and distribution of wheat.S significantly increased the plant N accumulation amount at different growth stages,N translocation amount from stem and sheath and leaf post-anthesis,grain N accumulation amount at maturity as compared to H.The nitrate reductase,glutamine synthetase activities and free amino acid content of flag leaves post-anthesis were higher in S than in H.In S,YN had higher plant N accumulation amount at anthesis and maturity stages,N translocation amount from stem and sheath and leaf post-anthesis,grain N accumulation amount at maturity as compared to JM and LX.The nitrate reductase,glutamine synthetase activities and free amino acid content of flag leaves at 20 DAA of YN were significantly higher than those of JM and LX.These results indicated that YN planting in S was beneficial to enhance the abilities of plant N absorption and N transport in vegetative organs,and improved the N accumulation in grain.Flag leaf senescence characteristics and root distribution of wheat.S had higher superoxide dismutase（SOD）activity,soluble protein（SP）concentration of flag leaves at 7,14,21 and 28 DAA,and higher trans zeatin riboside content of flag leaves post-anthesis as compared to H.The root weight density in the 40-100 cm soil layer at anthesis,root length density,root surface area density,root SOD activity,root SP concentration and root activities in the 0-40 cm soil layer at 10 and 20 DAA were higher in S than in H treatment.In S,the SOD activity of flag leaves at 21 and 28 DAA,SP concentration and trans zeatin riboside content of flag leaves during mid-to-late grain filling stage decreased in the order of YN>JM>LX.YN had higher root weight density in the 20-60 cm soil layer at anthesis,root length density,root diameter and root surface area density in the 0-40 cm soil layer at 20 DAA,root SOD activity,root SP concentration and root activities in the 0-40 cm soil layer at 10 and 20 DAA than JM and LX.These results indicated that YN planting in S contributed to delaying the leaf and root senescence.Grain yield and N use efficiency.Compared to H,S had higher spike number,1000-grain weight,grain yield and PFPN.In S,there were no significantly differences in spike number among different wheat varieties.YN had higher grain number,1000-grain weight,grain yield and PFPN than those of JM and LX.These results indicated that YN wheat variety planting in S was optimal for high yield and high efficiency of wheat in this study. |
