Nitrogen (N), as a macro-element, plays a vital role in plant growth and development. N deficiency affects plant productivity by decreasing photosynthesis, leaf area and longevity of green leaf. To date, many studies have reported that the relationship between photosynthesis and N supply. Here, we summarized the physiological response of photosynthesis to N deficiency in leaf structure and N allocation within the leaf. In serious N stress, photosynthetic rate decreases for almost all plants. The reasons as follows:(1) reducing stomatal conductance of mesophyll cell (g_s) and bundle sheath cells (g_bs) which influences intercellular CO₂ concentration; (2) reducing the content of bioenergetics and light-harvesting protein which inhibits electron transport rate and increase the light energy dissipated as heat; (3) reducing the content and/or activity of photosynthetic enzymes which reduces carboxylation rate. During reproductive stage, N stress induces plant senescence and N components degradation, especially photosynthetic enzymes and thylakoid N, and thus reduces photosynthesis. To keep high grain yield in low N deficiency, we should choose the genotype with higher N allocation within bioenergetics and lower degradation of photosynthetic enzymes. This review provides a generalized N allocation in response to N stress and gives a new prospect for breeding N-efficient genotypes.

氮（N）作为一种宏观元素，在植物生长发育中起着至关重要的作用。氮缺乏会通过降低光合作用，减少叶面积和延长绿叶的寿命来影响植物的生产力。迄今为止，许多研究已经报道了光合作用和氮供应之间的关系。在这里，我们总结了光合作用对叶片结构中氮缺乏和叶片中氮分配的生理响应。在严重的氮胁迫下，几乎所有植物的光合速率都会降低。原因如下：（1）降低了影响细胞间CO ₂的叶肉细胞（g _s）和束鞘细胞（g _bs）的气孔导度浓度; （2）减少生物能和光捕获蛋白的含量，抑制电子的传输速率，增加热量散发的光能。（3）降低光合酶的含量和/或活性，这降低了羧化速率。在生殖阶段，N胁迫诱导植物衰老，N组分降解，特别是光合酶和类囊体N降解，从而降低了光合作用。为了在低氮缺乏的情况下保持高产量，我们应该选择生物能学中氮分配较高且光合酶降解较低的基因型。这篇综述提供了响应于N胁迫的广义N分配，并为育种高效N基因型提供了新的前景。