Enhancing Nitrogen Use Efficiency (NUE) is extremely important towards mitigating climate change, especially in wheat where the NUE is less than 50%. Hence, optimizing grain yield under reduced application of nitrogenous fertilizer is a significant challenge. To address this challenge, a comprehensive study was conducted to investigate various agronomic traits and morphological, biochemical and molecular parameters related to NUE. This study explored their interrelationships and effects on grain yield, providing novel insights that were not previously reported. A set of 278 diverse wheat genotypes were assessed, encompassing eight NUE-related field traits. All traits' values were reduced under stressed N (ranging from 7.5% to 77.5%) except Nitrogen Utilization Efficiency (NUtE) and NUE. Data analysis showed a significant positive correlation between grain yield and all other NUE-related traits (r² value ranged from .23 to 1.00), highlighting their relevance in comprehending the biological NUE of wheat plants. Principal component analysis (PCA) also revealed that N at head and N at harvest were more connected with gain yield, NUE and biomass under the optimum N condition, but less connected with gain yield and NUE under the stressed N condition. To complement the field data, representative genotypes were further subjected to a hydroponics experiment under absolute N control to study the different morphological parameters, photosynthetic pigments and the performance of essential N- and C-metabolizing enzymes at the seedling stage. N stress had a detrimental impact on the majority of the parameters (−0.84% to −79.8%). Nitrite reductase (NiR), glutamate dehydrogenase (GDH) and isocitrate dehydrogenase (ICDH) enzymes as well as root length (RL), root fresh weight (RFW) and CS transcript, were positively affected by 5.9%–35.6%. The correlation analysis highlighted the substantial influence of four key N-metabolizing enzymes, namely nitrate reductase (NR), glutamine synthetase (GS), glutamate oxo-glutarate aminotransferase (GOGAT), and GDH on grain yield. Additionally, this study highlighted the direct and indirect associations between seedling parameters and field traits, where shoot and root length were found to be most significant for N acquisition, especially under N stress. In conclusion, these findings offer valuable insights into the intricate network of traits and parameters influencing wheat grain yield under varying N regimes.

中文翻译：

---

揭示与小麦氮利用效率相关的不同性状和参数之间的相互作用，以实现气候适应型农业

提高氮素利用效率 (NUE) 对于缓解气候变化极其重要，尤其是 NUE 低于 50% 的小麦。因此，在减少氮肥施用的情况下优化粮食产量是一个重大挑战。为了应对这一挑战，开展了一项综合研究，调查与 NUE 相关的各种农艺性状以及形态、生化和分子参数。这项研究探讨了它们之间的相互关系以及对粮食产量的影响，提供了以前未报道过的新见解。对 278 个不同的小麦基因型进行了评估，其中包括八个与 NUE 相关的田间性状。除氮利用效率（NUtE）和NUE外，所有性状值在氮胁迫下均降低（范围为7.5%至77.5%）。数据分析显示，谷物产量与所有其他 NUE 相关性状之间存在显着正相关性（r ²值范围为 0.23 至 1.00），突出了它们在理解小麦植株生物 NUE 方面的相关性。主成分分析(PCA)还表明，在最佳氮条件下，穗氮和收获时氮与增产、氮利用效率和生物量的相关性较高，但在氮胁迫条件下，与增重产量和氮肥的相关性较小。为了补充田间数据，对代表性基因型进一步进行了绝对氮控制下的水培实验，以研究苗期不同形态参数、光合色素以及必需的氮和碳代谢酶的性能。氮胁迫对大多数参数都有不利影响（-0.84％至-79.8％）。亚硝酸盐还原酶 (NiR)、谷氨酸脱氢酶 (GDH) 和异柠檬酸脱氢酶 (ICDH) 以及根长 (RL)、根鲜重 (RFW) 和CS转录本受到 5.9%–35.6% 的正向影响。相关分析强调了四种关键的氮代谢酶，即硝酸还原酶（NR）、谷氨酰胺合成酶（GS）、谷氨酸氧代-戊二酸转氨酶（GOGAT）和GDH对谷物产量的显着影响。此外，这项研究强调了幼苗参数与田间性状之间的直接和间接关联，其中芽和根长度被发现对于氮获取最重要，特别是在氮胁迫下。总之，这些发现为了解不同氮条件下影响小麦籽粒产量的性状和参数的复杂网络提供了宝贵的见解。