对在不同温度条件下越冬的柑橘苗光合能力和生长活性进行研究的结果显示，室外橘苗在冬季光合能力的下降，主要是由于低温作用于叶子的后效，而不是由于植株或器官的休眠状态．光合降低的程度和升温后光合恢复所需的时间随低温处理时间的增长而增加．光合下降过程中叶子细胞间隙与环境中ＣＯ２浓度的比值最初比较恒定，然后逐渐增大．这一事实表明，降温初期气孔导度和叶肉导度同时协调地下降，以后叶肉导度的下降逐渐占据优势，而在恢复过程中则相反．仅仅茎部或根部受低温处理也会导致光合能力的明显降低．然而不同的低温处理方式对叶子水势的影响有明显差别．所以低温通过减少供水造成叶子水分亏缺虽然可能是导致光合下降的原因之一，但不像是唯一的原因．在完全没有光参与的条件下单靠低温就足以使光合能力明显下降，可是不能排除冬季在田间条件下同时也发生因低温而加强的光抑制． The results of research on the photosynthetic capacity and growth activity of citrus seedling overwintering under different temperature conditions showed that the decrease of photosynthetic capacity of outdoor tangerine seedlings in winter was mainly due to the effect of low temperature on the leaf afterglow but not the dormancy of plants or organs status. The degree of photosynthesis reduction and the time required for photosynthetic recovery after warming increase with increasing cold treatment time. During photosynthetic decline, the ratio of leaf cell interspace to CO2 concentration in the environment was initially relatively constant and then gradually increased. This fact indicates that stomatal conductance and mesophyll conductance decrease in coordination at the same time in the early stage of temperature drop, and then the decline of mesophyll conductance gradually takes the advantage, while the opposite is true during the recovery process. The mere treatment of the stems or roots with low temperature can also result in a significant decrease in photosynthetic capacity. However, the effect of different low temperature treatments on leaf water potential is obviously different. So low temperature water deficit by reducing water supply may be one of the reasons leading to photosynthesis decline, but not the only reason. Under the condition of no light participation alone, the low temperature alone is enough to significantly reduce the photosynthetic capacity, but it can not be excluded that the light suppression enhanced by the low temperature also occurs in the field in winter at the same time in winter.