A test of the hydraulic vulnerability segmentation hypothesis in angiosperm and conifer tree species
A test of the hydraulic vulnerability segmentation hypothesis in angiosperm and conifer tree species
复制标题
DOI：
10.1093/treephys/tpw031
复制
发表时间：
2016-08-01
期刊：
影响因子：
4
通讯作者：
Domec, Jean-Christophe
中科院分区：
文献类型：
--
作者：
Johnson, Daniel M.;Wortemann, Remi;Domec, Jean-Christophe
水分从土壤向大气的输送对植物的生长和存活至关重要。然而，我们有一个有限的了解全树水力通路的许多部分，因为绝大多数已发表的信息是终端分支。特别是我们对成熟树干的水力生理的了解是有限的。水力脆弱性分割假说（HVSH）规定，植物的远端部分（叶，枝和根）应该比树干更容易受到栓塞的影响，树干是需要大量碳投资的非冗余器官。在目前的研究中，我们比较了脆弱性损失的水力功能，叶和木质部的水潜力和由此产生的水力安全裕度（在有关的水潜力造成50%的损失导水率）在叶，树枝，树干和根的四个被子植物和针叶树种。在所有物种中，我们的研究结果强烈支持HVSH，因为叶和根对栓塞的抵抗力低于分支或树干。然而，树枝始终比植物的任何其他部分（包括树干）更能抵抗栓塞。此外，计算出的全树液压功能障碍的脆弱性是远远大于分支机构的脆弱性。这是由于根和叶中的水力功能障碍比那些引起分支或主干功能障碍的负水势小。叶和根具有狭窄或负的水力安全裕度，但树干和树枝保持正的安全裕度。通过使用基于分支的水力信息作为整个植物的代理，许多研究可能高估了许多物种的抗栓塞性和耐旱性。这项研究强调了重新考虑过去仅基于分支木质部的植物抗旱性的结论的必要性。本研究还强调了需要更多的研究全植物的水力生理，以更好地了解植物耐旱性的策略和水力途径中的关键控制点。
Water transport from soils to the atmosphere is critical for plant growth and survival. However, we have a limited understanding about many portions of the whole-tree hydraulic pathway, because the vast majority of published information is on terminal branches. Our understanding of mature tree trunk hydraulic physiology, in particular, is limited. The hydraulic vulnerability segmentation hypothesis (HVSH) stipulates that distal portions of the plant (leaves, branches and roots) should be more vulnerable to embolism than trunks, which are nonredundant organs that require a massive carbon investment. In the current study, we compared vulnerability to loss of hydraulic function, leaf and xylem water potentials and the resulting hydraulic safety margins (in relation to the water potential causing 50% loss of hydraulic conductivity) in leaves, branches, trunks and roots of four angiosperms and four conifer tree species. Across all species, our results supported strongly the HVSH as leaves and roots were less resistant to embolism than branches or trunks. However, branches were consistently more resistant to embolism than any other portion of the plant, including trunks. Also, calculated whole-tree vulnerability to hydraulic dysfunction was much greater than vulnerability in branches. This was due to hydraulic dysfunction in roots and leaves at less negative water potentials than those causing branch or trunk dysfunction. Leaves and roots had narrow or negative hydraulic safety margins, but trunks and branches maintained positive safety margins. By using branch-based hydraulic information as a proxy for entire plants, much research has potentially overestimated embolism resistance, and possibly drought tolerance, for many species. This study highlights the necessity to reconsider past conclusions made about plant resistance to drought based on branch xylem only. This study also highlights the necessity for more research of whole-plant hydraulic physiology to better understand strategies of plant drought tolerance and the critical control points within the hydraulic pathway.