| Due to greenhouse effect, global surface temperature is predicted to continue to increase in the future. Nitrogen (N) is an important agricultural input that is critical for crop production. Growth temperature and nitrogen application both significantly affect the formation of grain yield and quality during the whole growth stage in wheat. Physiological effects of nitrogen application on grain yield and quality under temperature increase scenario in wheat should have important implications for climatic impact studies. In a field trial, winter wheat (Triticum aestivum L.) cultivar Yannong19, an elite wheat landrace in Lianyungang was grown to clarify the combined effects of N application and temperature increase on grain yield and quality in wheat. Combined effects of N application and temperature increase on carbon and nitrogen metabolize and formation of yield and quality in wheat were investigated. The main results were following:1. Effects of different nitrogen rates on grain yield and quality under temperature increase scenario in wheat.TI (temperature increased2℃during whole growth period) significantly increased wheat grain yield, by27.91%,13.64%,6.38%and12.57%, respectively, in treatment of NO, N150, N225and N300. Spike number and kernel per spike were both improved as increased N application rate, while1000-kernel weight reduced, thus the final grain yield was highest in N225. TI increased contents of protein, dry and wet gluten, while reduced total starch content, falling number, peak viscosity, hold trough and final viscosity in Yannong19. Moreover, TI also increased glutenin macropolymer (GMP) content and high molecular weight glutenin subunits (HMW-GS) accumulation amount during grain filling. Under2℃warming during whole growth period, contents of total protein, dry and wet gluten, and SDS-sedimentation volume were increased, while content of total starch, peak viscosity, hold trough, breakdown and final viscosity were decreased with increased total N application rate. 2. Effects of different nitrogen rates on carbon and nitrogen metabolism under temperature increase scenario in wheat.TI (temperature increased2℃during whole growth period) increased chlorophyll content (SPAD) and alleviated senescence of flag leaf. Furthermore, TI also increased contents of total soluble sugar and sucrose, as well as grain filling rate, promoted dry matter accumulation and pre-anthesis matter redistribution, thus accounted for grain yield improvement. Contents of free amino acid and total nitrogen (N) after anthesis were increased under TI treatment, along with the increased pre-anthesis nitrogen redistribution, which contributed to the improved protein accumulation in grain. Whereas, contents of total soluble sugar and sucrose were decreased, grain filling rate and dry matter accumulation was reduced by increased N application rate, pre-anthesis matter redistribution was also impeded, higher N application rate improved free amino acid content and total N content and accumulation amount, promoted pre-anthesis nitrogen redistribution, which finally lead to higher protein content of grain.3. Effects of different nitrogen rates on nitrogen use efficiency under temperature increase scenario in wheat.It could be noted that TI and higher N application rate both reduced nitrogen use efficiency (NUE). Warming temperature and higher nitrogen application rate both increased final grain nitrogen accumulation and nitrogen recycling efficiency, while dereased nitrogen dry matter production efficiency, nitrogen production efficiency and nitrogen agronomic efficiency, with a result of lower NUE.In conclusion, dry matter accumulation was improved by warming temperature while reduced by higher N application. However, N assimilation translocation was increased by both enhanced temperature and higher N application, leading to higher final yield and protein quality, while lower starch quality of grain in wheat. |
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