Effects of Nitrogen Application Strategy on Nitrogen Enzyme Activities and Protein Content in Spring Wheat Grain

Abstract

The aim of this study was to determine the regulatory effect of different nitrogen (N) fertilizer application rates on the grain N metabolism enzymes and protein content of drip-irrigated spring wheat under the climatic conditions in Xinjiang, China. A split plot experiment was conducted with strong gluten wheat Xinchun 38 (XC 38) and medium gluten wheat Xinchun 49 (XC 49) as experimental materials. We set up seven nitrogen treatments, in amounts of 300 (Nck), 285 (N5), 270 (N10), 255 (N15), 240 (N20), 225 (N25) and 0 (N0) kg hm−2. The effects of N application rate on nitrate reductase (NR), glutamine synthetase (GS), glutamate-pyruvate aminotransferase (GPT), protein content, protein composition, and yield of wheat grain were studied. The results showed that NR, GS, GPT, protein content, albumin, globulin, glutenin, gliadin, and yield first increased and then decreased with the decrease in N application. Furthermore, different responses to different applications between different wheat varieties was also observed. The indexes of XC 38 reached the maximum in the N15 treatment, and the yield increased 2.99~81.45%. XC 49 showed the best indicators under the N25 treatment and the yield increased 0.37~71.29%. Under the same N level, all indicators of XC 38 were better than XC 49. Correlation analysis showed that the yield and protein yield were significantly positively correlated with NR, GS, and GPT. The interaction of N fertilizer and variety had significant effects on NR, GS, GPT, protein content, components, and yield. These results show that the protein content and yield of wheat grain can be improved by reasonably adjusting the N fertilizer application strategy.