Abstract:

In response to the issues of excessive nitrogen fertilizer application in tobacco production leading to quality deterioration and environmental pollution, as well as the unclear mechanisms of nitrogen utilization, lack of precise nitrogen application standards, and undefined breeding targets, this paper reviewed the absorption, distribution, and utilization mechanisms of nitrate and ammonium nitrogen in tobacco to improve the theoretical framework of nitrogen nutrition regulation and nitrogen-efficient improvement technologies. The functions and expression characteristics of nitrogen transporters (NRT and AMT families) in tobacco were summarized, key factors involved in nitrogen sensing and signal transduction (such as nitrate receptors and transcription factors) and regulatory pathways were analyzed, and the main approaches and genetic improvement progress for enhancing nitrogen efficiency were outlined. The results indicated that: (1) Tobacco absorbed nitrate and ammonium nitrogen through high-/low-affinity transport systems, with assimilation relying on key enzymes such as nitrate reductase (NR), nitrite reductase (NiR), and glutamine synthetase (GS). (2) The NRT family primarily mediated nitrate nitrogen transport, while the AMT family regulates ammonium nitrogen absorption. Transcription factors such as NtWRKY65 participated in nitrogen signal transduction. (3) The optimal nitrogen application rates varied significantly across different tobacco-growing regions (100-150 kg/hm² in southern China and 82.5-90 kg/hm² in northern China), with a NO₃^-/NH₄⁺ ratio of 1:1 being suitable for most varieties. (4) Dual high-efficiency varieties such as K326 and G80 had been identified, and nitrogen efficiency-related indicators such as leaf area and enzyme activity had been clarified. In summary, tobacco nitrogen nutrition regulation involved the coordinated actions of multiple processes, including absorption, transport, and signal transduction, with rational fertilization and varietal improvement being the core pathways for enhancing nitrogen efficiency. Future efforts should focus on conducting multi-regional trials to define precise nitrogen application parameters, identifying key molecular targets in nitrogen metabolism, and integrating molecular techniques with traditional breeding to develop nitrogen-efficient varieties, thereby providing support for green tobacco production.

Key words: tobacco, nitrogen nutrition, nitrogen transport proteins, nitrogen signal transduction, nitrogen-efficient varieties