Preanthesis Root Growth and Nitrogen Uptake Improved Wheat Grain Yield and Nitrogen Use Efficiency

Abstract

Grain yield and N fertilizer use efficiency (NUE) are closely related to preanthesis root growth and distribution, whereas changes in root morphology and distribution, plants’ N uptake and utilization ability, and their relationships with grain yield and NUE remain unclear. We conducted a 2‐yr microplot and sand culture experiment using three wheat (Triticum aestivum L.) cultivars (N‐efficient, intermediate, and N‐inefficient) to examine differences in grain yield, NUE, root growth, root morphology, root distribution, and nitrate transporter gene (TaNRT) expression. The N‐efficient wheat cultivar increased grain yield and NUE by improving preanthesis N uptake. Root biomass, growth rate, length, surface area, and weight density were higher in the N‐efficient cultivar than in other cultivars at preanthesis. The N‐efficient cultivar distributed more roots throughout the topsoil layer. The TaNRT expression level at preanthesis was higher in the N‐efficient cultivar than in the intermediate cultivar, whereas no significant genotypic difference was observed after anthesis. This result indicates that TaNRT upregulation increased N efficiency through a higher preanthesis N uptake and that TaNRT 1.1 and TaNRT 1.2 played a more important role than TaNRT 2.1 and TaNRT 2.2. Nitrate reductase and glutamine synthetase activity increased in the N‐efficient cultivar at the preanthesis stage and decreased after anthesis. These results indicate that the N‐efficient wheat cultivar had higher preanthesis root growth and N uptake ability, promoting leaf N assimilation ability and improving wheat yield and NUE.Core Ideas Yield and N use efficiency were comparable among different N‐efficient wheat cultivars. The N‐efficient wheat cultivar increased preanthesis N accumulation. The N‐efficient wheat cultivar showed faster root growth and greater root distribution in the soil.