Hydraulic Failure Defines the Recovery and Point of Death in Water-Stressed Conifers
Hydraulic Failure Defines the Recovery and Point of Death in Water-Stressed Conifers
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DOI：
10.1104/pp.108.129783
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发表时间：
2009-01-01
期刊：
影响因子：
7.4
通讯作者：
Cochard, Herve
中科院分区：
文献类型：
--
作者：
Brodribb, Tim J.;Cochard, Herve
本研究结合现有的水力原理与最近开发的方法探测叶水力功能，以确定木质部生理是否可以解释在干旱和复水后的恢复阶段的气体交换的动态响应。从潮湿和干燥的森林针叶树种暴露于一系列的水分胁迫，通过扣水，然后再浇水，以观察恢复过程。在这两个阶段，中午蒸腾和叶水势（PSI（叶））进行了监测。气孔对PSI（叶）的反应，建立了每个物种和这些关系用于评估是否恢复干旱后的气体交换是有限的stembolism液压修复叶片。此外，气体交换恢复的时间被用来确定每个物种的最大生存水分胁迫和这个指数相比，每个物种的叶片和茎的脆弱性，水分胁迫引起的功能障碍的数据。水分胁迫后气体交换的恢复需要1至> 100 d，在此期间，所有物种都表现出强烈的1：1符合水力-气孔限制模型（所有植物的r（2）= 0.70）。气体交换恢复时间显示出两个不同的阶段，在胁迫至叶片水力传导度（K-叶）损失< 50%的植物中的快速过夜恢复和在胁迫至K-叶损失> 50%的植物中的高度Psi（叶）依赖性阶段。最大可恢复的水分胁迫（PSI（分钟））对应于95%的K叶损失。因此，我们的结论是木质部水力学代表了这些针叶树种耐旱性的直接限制。
This study combines existing hydraulic principles with recently developed methods for probing leaf hydraulic function to determine whether xylem physiology can explain the dynamic response of gas exchange both during drought and in the recovery phase after rewatering. Four conifer species from wet and dry forests were exposed to a range of water stresses by withholding water and then rewatering to observe the recovery process. During both phases midday transpiration and leaf water potential (Psi(leaf)) were monitored. Stomatal responses to Psi(leaf) were established for each species and these relationships used to evaluate whether the recovery of gas exchange after drought was limited by postembolism hydraulic repair in leaves. Furthermore, the timing of gas-exchange recovery was used to determine the maximum survivable water stress for each species and this index compared with data for both leaf and stem vulnerability to water-stress-induced dysfunction measured for each species. Recovery of gas exchange after water stress took between 1 and > 100 d and during this period all species showed strong 1: 1 conformity to a combined hydraulic-stomatal limitation model (r(2) = 0.70 across all plants). Gas-exchange recovery time showed two distinct phases, a rapid overnight recovery in plants stressed to < 50% loss of leaf hydraulic conductance (K-leaf) and a highly Psi(leaf)-dependent phase in plants stressed to > 50% loss of K-leaf. Maximum recoverable water stress (Psi(min)) corresponded to a 95% loss of K-leaf. Thus, we conclude that xylem hydraulics represents a direct limit to the drought tolerance of these conifer species.