Premise Water stored in the xylem of woody plants is important for supporting the transpiration stream under prolonged drought, yet the source of stored water within the xylem during drought remains unclear. Insights into xylem water utilization during drought will uncover the adaptation strategies of the test species to stress. Methods To fill the existing knowledge gap, we excised twigs of Abies firma (Japanese fir, conifer), Cercidiphyllum japonicum (katsura tree, diffuse‐porous) and Quercus serrata (konara oak, ring‐porous) to quantify interspecific variation of water transfer in xylem corresponding with increasing cumulative water release (CWR) using micro x‐ray computed tomography and cryo‐SEM. Results For all species studied, the main components of water storage within the operating range of water potential were not living cells but cavitation release and capillaries. Abies firma maintained water in the earlywood‐like cells, for possible maintenance of the transpiration stream. Cercidiphyllum japonicum maintained water in its vessels over 200 kg m‐3 of CWR, while Q. serrata lost most of its water in vessels with increasing CWR up to 100 kg m‐3. Cercidiphyllum japonicum exhibited a higher water storage capacity than Q. serrata. Under high CWR, narrow conduits stored xylem water in C. japonicum and imperforate tracheary elements in Q. serrata. Conclusions Among the species examined, increasing CWR appears to indicate differential utilization of stored water in relation to variation of xylem structure, thereby providing insight into the interspecific responses of tree species to drought.

中文翻译：

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无孔气管元件和血管在严重脱水下减轻木质部张力：从三种树种切下树枝的水释放曲线中获得见解

前提 储存在木本植物木质部的水对于在长期干旱下支持蒸腾流很重要，但干旱期间木质部内储存的水的来源仍不清楚。对干旱期间木质部水分利用的深入了解将揭示测试物种对压力的适应策略。方法为了填补现有的知识空白，我们切除了冷杉（日本冷杉，针叶树）、连香树（桂树，漫孔）和锯缘栎（科纳拉橡树，环孔）的枝条，以量化水转移的种间变异木质部对应于使用显微 X 射线计算机断层扫描和冷冻扫描电镜增加累积水释放量 (CWR)。结果 对于所有研究的物种，水势运行范围内蓄水的主要成分不是活细胞，而是空化释放和毛细血管。冷杉在早期木材样细胞中保持水分，以便可能维持蒸腾流。Cercidiphyllum japonicum 在其容器中保持水超过 200 kg m-3 的 CWR，而 Q. serrata 在容器中失去大部分水，CWR 增加到 100 kg m-3。Cecidiphyllum japonicum 表现出比 Q. serrata 更高的储水能力。在高 CWR 下，狭窄的管道在 C. japonicum 中储存木质部水，在 Q. serrata 中储存气管元件。结论 在检查的物种中，增加 CWR 似乎表明储存水的不同利用与木质部结构的变化有关，