Objective]Growth of trees is strongly influenced by climatic factors. The changes of xylem cells of trees record more detailed information compared to the tree-ring widths,and could enrich the present knowledge extracted from the traditional dendroclimatological or dendroecological studies. Our aim is to provide a reference for studying the global change using the characteristics of trees xylem cells.[Method]This paper summarizes the process of xylem formation,the research methods of studying the responses of xylem growth to climatic factors and the effect of climatic change ( temperature,precipitation,solar radiation,photoperiod and increasing atmospheric CO2 ) on trees cambial activity and xylem growth. [Result]At present,there are two methods to study the response of xylem growth to climatic factors at cell level: pinning and microcoring. Pinning was mainly used to study the response of cambium to injury or records the xylem growth increment of tropical trees,and microcoring can be used to observe the changes of the number of cambium cells in different stages and the xylem formation process. Recent research demonstrated that the formation of xylem went through four stages: cambial reactivation,cell radial enlargement,secondary wall thickening and lignification,the formation of mature xylem cells, and each stage was affected by climatic factors. The changes of xylem growth of trees were significantly correlated with some climatic factors,such as temperature,precipitation,solar radiation,photoperiod and increasing atmospheric CO2 . Temperature mainly affects the cambium activity at early stage of tree growth,and changes the time of reactivation of the cambium,cell division rate and active period. But temperature will not change the sequence of xylem cell differentiation and seasonal growth pattern. Precipitation mainly affects the rate of the cambium cell division, the duration of cambium cell division in the growing season and the tracheid diameter. Inadequate precipitation could reduce the rate of cell division,shorten the time of cell differentiation,and result in a decrease in the duration of cambium activity. Meanwhile,precipitation shortage could inhibit cell stretch,and the lumen diameter become small. Light intensity affects indirectly the activity of cambium cells through affecting photosynthesis. Photoperiod mainly controls the maximum growth rate of xylem cells and the end of growing period. Up to now,no consistent conclusions was reported about the relationship between the growth of xylem cells and the increasing atmospheric CO2 . Some studies suggested that elevated CO2 concentrations affect the rate of the cell division and cell expansion rather than the secondary cell wall thickening,and result in a significant increase in the width of early wood growth ring. Some experimental evidences also showed that elevated CO2 concentrations did not cause larger changes of early wood cell structure. Conversely,the width of late wood growth ring increased obviously. [Conclusion]With the development of research theory and technology,the growth characteristics of xylem cells under extreme climate,the growth responses of xylem cells in different tree species to climate change and the comprehensive effect of a variety of climate factors on trees xylem growth will become the main direction of future research.%【目的】树木生长受多种气候因子的影响，与年轮宽度相比，树木木质部细胞的生长变化记录了更为详尽的气候信息，可以丰富当前从传统树轮气候学或树轮生态学研究中所得到的认识。本研究以期为利用树轮木质部细胞特征研究全球变化提供参考。【方法】综述了树木木质部形成过程、研究木质部细胞生长变化对气候因子响应的常用方法以及气候变化(温度、降水、光照强度、光周期和CO2浓度等)对形成层活动及木质部细胞生长变化的影响。【结果】目前，在细胞水平上研究树木木质部生长变化对气候因子响应过程的主要方法为：钉针法和微芯取样法，钉针法主要适用于研究形成层对损伤的响应或是记录热带树木木质部生长的增量，而微芯取样法可以清楚地观察到生长季各阶段形成层细胞数量的变化及木质部形成过程；树木木质部的生长过程一般从形成层恢复活动开始，经过细胞的伸展、次生细胞壁的加厚和木质化后，形成成熟的次生木质部细胞，其中的每一个阶段都会受到气候因子变化的影响；树木木质部细胞生长的变化与温度、降水、光照强度、光周期和 CO2浓度等气候因子有着复杂的相关关系；温度主要影响树木生长季前期形成层的活动，改变形成层恢复活动的时间、细胞的分裂速率及活动周期，但并不会改变木质部细胞分化的序列和季节生长模式；降水主要影响形成层细胞分裂的速率、在生长季的持续时间以及管胞的直径等，降水不足会降低树木细胞分裂的速率，缩短细胞分化的时间，导致生长季的持续时间减少，同时抑制细胞伸展，管腔直径较小；光照强度主要影响树木的光合速率来间接影响形成层细胞的活动；光周期主要控制木质部细胞的最大生长速率和生长结束期；有关 CO2浓度升高对树木木质部细胞的影响，研究结果并不一致，一些研究认为，CO2浓度升高影响细胞的分裂速率和细胞的扩张而不是次生细胞壁的加厚，从而造成早材生长轮宽度明显增加，但也有研究表明，CO2浓度升高并没有引起早材细胞结构较大的变化，相反晚材生长环的宽度却明显增加。【结论】随着研究理论和技术手段的不断成熟，极端灾害下树木木质部细胞的生长特征、不同树种木质部细胞的生长对气候变化的响应以及多种气候因子对树木木质部生长的综合影响将成为今后研究的主要方向。
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