在全球变化条件下，温度的升高和降水格局的变化，导致淡水资源更加匮乏。环境因子胁迫，如干旱和高温等，它们单独或联合的作用将导致作物大幅度减产，引发自然生态系统退化。植物的碳氮代谢及其分配相互联系、不可分割，其生物过程及外界环境调节共同决定着植物的净生产力和营养水平。该文试图从分子、组织、器官、个体和生态系统等层面上，就植物的碳氮关系及其环境调节（温度、水分和CO2浓度等）进行综述，并提出了进一步展开相关研究应重点关注的几个方面。
Globally elevated temperatures and changed precipitation distributions may lead to deficits of fresh water that reduce crop yields and degrade natural ecosystems. Plant carbon (C) and nitrogen (N) metabolism and its abiotic environmental regulation are responsible for net primary productivity and plant nutrient status. We review the relationship between C and N and regulation by environmental factors such as temperature, water moisture and CO2 enrichment at multiple levels of plant organization, including molecule, tissue, organ, whole plant and ecosystem. For cereal crops including wheat and rice, grain N mainly includes: 1) N reallocated in vegetative organs before anthesis, and 2) N absorbed from soil after anthesis. Their proportions depend on the activity and size of grains as an N sink and species and cultivars, affecting the grain yield and quality. Leaf N level can explain 45%-75% of leaf photosynthesis, and 71%-88% of leaf N can be allocated into protein, with Rubisco, the key enzyme for photosynthesis, accounting for 30%-50% of total leaf soluble protein, making it the protein using most N. Furthermore, the N proportions among the photosynthetic organs and the ratio between soluble sugar and starch may be associated with the Rubisco gene. Therefore, plant N level may be assessed by photosynthetic capacity. Many studies have demonstrated that drought can promote C allocation to below-ground parts of plants, increasing root∶shoot biomass ratio. There is, however, evidence that this enhancement of roots due to moderate drought can be negated by severe drought. On the other hand, drought also increases N concentration in sink organs, such as wheat grains, and decreases mature leaf N concentration, decreasing leaf net photosynthetic rate. However, high temperature does not significantly increase C allocation to roots, but may decrease leaf N concentration and affect Rubisco level. Thus, a decline of photosynthetic capacity induced by above optimal temperature, particularly at night, may be ascribed to an adverse effect on photosystemⅡ(PSⅡ). Generally, elevated CO2 dilutes plant tissue N, leading to a lower C∶N ratio that may come from the effect on Rubisco expression. Whole ecosystem N allocation and cycle can be affected by elevated CO2, thereby changing ecosystem structure and function. The interaction between severe drought and high temperature can lead to a decrease in leaf N, reducing plant C-fixing ability, depending on the time and severity of stresses. Under high CO2 concentration and drought, the C allocation into below-ground parts can be enhanced and the C∶N ratio may increase. The interaction between elevated CO2 and high temperature can alter plant tissue N allocation, with elevated CO2 increasing CO2 site activity of Rubisco and decreasing N investment in photosynthetic apparatus, but high temperature increasing O2 site activity of Rubisco and increasing N investment. Nevertheless, under global change conditions, the combined effects from various stress factors are complex, and may include both positive and negative relationships. Research is urgently needed to 1) elucidate plant C and N allocation models from molecular to ecosystem levels; 2) address synergistic effects of multiple environmental stresses; 3) predict C and N allocation based on different global change scenarios; 4) quantify the threshold for change in C and N allocation in response to global change; and 5) strengthen knowledge of the key role of C and N allocation in agricultural and forest productivity and conservation of natural ecosystems.