中文摘要：

维持木本植物体内长距离的水分运输对于植物生存、生长和发育非常重要,但因水分在木质部张力状态下处于亚稳定状态而易发生空穴化和栓塞,导致水力导度降低、生产力下降、甚至植物死亡。面对水分胁迫诱导的空穴化,植物可通过形成抵抗空穴化的解剖结构降低栓塞发生频率,或（和）通过活跃的代谢修复栓塞,其中对木质部栓塞及其修复的发生频率、条件、机制等的认识仍有很大分歧。为此,该文首先综述了木质部栓塞修复过程及时间动态、木质部栓塞形成及修复的发生频率。然后,总结了木质部导管“新的再充水”栓塞修复过程中的4种主要假说：（1）渗透调节假说;（2）反渗透调节假说;（3）韧皮部驱动再充水假说;（4）韧皮部卸载假说。在此基础上,比较了针叶树种和木本被子植物木质部栓塞形成与修复的差异,并分析了木质部栓塞阻力与修复能力之间的权衡关系。最后,提出了木本植物木质部栓塞与修复研究的4个优先研究问题：（1）改进木质部栓塞测定技术;（2）验证“新的再充水”栓塞修复机制假说及引发木质部再充水的信号;（3）阐明木质部栓塞与修复特性的树种间差异及其可能的权衡关系;（4）加强碳代谢和水通道蛋白表达与木质部栓塞及其修复关系的生理生化研究。

英文摘要：

To maintain long-distance water transport in woody plants is critical for their survival, growth and development. Water under tension is in a metastable state and prone to cavitation and embolism, which leads to loss of hydraulic conductance, reduced productivity, and eventually plant death. In face to water stress-induced cavitation, plants either reduce frequency of embolism occurrence through cavitation resistance with specialized anatomical structure, or/and form a metabolically active embolism repair mechanism. For the xylem embolism and repair, however, there are controversies regarding the occurring frequency, conditions and underlying mechanisms. In this review paper, we first examined the process, temporal dynamics and frequency of xylem embolism and repair. Then, we summarized hypotheses for the mechanisms of the novel refilling in xylem embolism repair, including the osmotic hypothesis, the reverse osmotic hypothesis, the phloem-driven refilling hypothesis, and the phloem unloading hypothesis. We further compared differences in xylem embolism and repair between conifers and angiosperms tree species, and examined the trade-offs between cavitation resistance and xylem recovery performance. Finally, we proposed four priorities in future research in this field： （1） to improve measuring technology of xylem embolism; （2） to test hypotheses for the mechanisms of the novel refilling in xylem embolism repair and the signal triggering xylem refilling; （3） to explore species-specific trait differences related to xylem embolism and repair and their underlying trade-off relationships; and （4） to enhance studies on the relationship between the involvement of carbon metabolism and aquaporins expression in xylem embolism and repair.