Yin Xiao Han, Hao Guang You
Key Laboratory of Forest Ecology and Management, Institute of Applied Ecology, Chinese Academy of Science, Shenyang 110016, Liaoning, China.
University of Chinese Academy of Sciences, Beijing 100049, China.
Ying Yong Sheng Tai Xue Bao. 2018 Feb;29(2):352-360. doi: 10.13287/j.1001-9332.201802.035.
Hydraulic characteristics of trees are strongly influenced by their xylem structures. The divergence in wood type between ring-porous and diffuse-porous species is expected to lead to significantly different hydraulic architecture between these two functional groups. However, there is a lack of comprehensive comparative studies in hydraulic traits between the two groups, in that no study has compared the whole-shoot level hydraulic conductance and detailed pit-level xylem anatomy has not been reported yet. In the present study, detailed hydraulic related traits were stu-died in three ring-porous and four diffuse-porous tree species commonly found in the broadleaf tree species of the Changbai Mountains, including whole-shoot hydraulic conductance (K), resis-tance to drought-induced embolism (P), and detailed tissue- and pit-level anatomical characteristics. Our results showed that: 1) consistent with the differences in stem hydraulic conductivity, ring-porous species showed significantly higher K but significantly lower resistance to drought-induced embolism, i.e., higher P, indicating a trade-off between hydraulic efficiency and safety in those two functional groups; 2) consistent with their significant divergence in hydraulic functions, the two functional groups showed significant differences in a suite of xylem anatomical characteristics at both the tissue and pit levels, such as maximum vessel length, vessel diameter, pit aperture area and aperture fraction; 3) significant correlations were identified between xylem structural characteristics and between structure and functions across both functional groups, indicating that differences in hydraulic functions were underlain by divergences in a suite structural traits. The competing structural requirements between different hydraulic traits, such as between shoot hydraulic conductance and resistance to drought-induced embolism, reflected the biophysical constraints of xylem design that could not fulfill multiple requirements of xylem functioning at the same time.
树木的水力特性受到其木质部结构的强烈影响。预计环孔材和散孔材物种之间木材类型的差异会导致这两个功能组之间的水力结构显著不同。然而，目前缺乏对这两组之间水力特性的全面比较研究，因为尚无研究比较过全枝水平的水力导度，且尚未有关于详细的纹孔水平木质部解剖结构的报道。在本研究中，对长白山阔叶树种中常见的三种环孔材和四种散孔材树种的详细水力相关特性进行了研究，包括全枝水力导度（K）、抗旱栓塞能力（P）以及详细的组织和纹孔水平的解剖特征。我们的结果表明：1）与茎干水力传导率的差异一致，环孔材物种表现出显著更高的K值，但抗旱栓塞能力显著更低，即P值更高，这表明这两个功能组在水力效率和安全性之间存在权衡；2）与它们在水力功能上的显著差异一致，这两个功能组在组织和纹孔水平的一系列木质部解剖特征上存在显著差异，如最大导管长度、导管直径、纹孔口面积和开口率；3）在两个功能组中均发现木质部结构特征之间以及结构与功能之间存在显著相关性，这表明水力功能的差异是由一系列结构性状的差异所导致的。不同水力特性之间相互竞争的结构要求，如枝水力导度和抗旱栓塞能力之间的要求，反映了木质部设计的生物物理限制，即无法同时满足木质部功能的多种需求。
