Coordination of stem and leaf hydraulic conductance in southern California shrubs: a test of the hydraulic segmentation hypothesis
Coordination of stem and leaf hydraulic conductance in southern California shrubs: a test of the hydraulic segmentation hypothesis
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DOI：
10.1111/nph.12850
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发表时间：
2014-08-01
期刊：
影响因子：
9.4
通讯作者：
Santiago, Louis S.
中科院分区：
文献类型：
--
作者：
Pivovaroff, Alexandria L.;Sack, Lawren;Santiago, Louis S.
植物器官间水分运动的协调性对于理解植物水分利用策略具有重要意义。水力分割假说（Hydraulic segmentation hypothesis，HSH）认为，生命周期较短的“消耗性”器官（如叶片）和生命周期较长的“昂贵性”器官（如茎）的水力传导率可能是分离的，叶片的阻力是瓶颈或“安全阀”。我们还通过将Kleaf与水力安全裕度（茎水势减去失去50%传导性的水势（Psi（茎）- Psi（50）相关联来研究叶片是否起到安全阀的作用。研究结果表明，水分胁迫下，叶片含水量与叶片含水量呈显著负相关，支持HSH理论。此外，Kleaf与水力安全裕度呈正相关，与叶面积边材面积比呈负相关，与HSH一致，我们的数据表明，叶片可能作为控制阀的物种与高KS，或低安全裕度。叶子的这一关键作用似乎对干旱易发环境中的植物生态专业化做出了重要贡献。
Coordination of water movement among plant organs is important for understanding plant water use strategies. The hydraulic segmentation hypothesis (HSH) proposes that hydraulic conductance in shorter lived, 'expendable' organs such as leaves and longer lived, more 'expensive' organs such as stems may be decoupled, with resistance in leaves acting as a bottleneck or 'safety valve'.We tested the HSH in woody species from a Mediterranean-type ecosystem by measuring leaf hydraulic conductance (K-leaf) and stem hydraulic conductivity (K-S). We also investigated whether leaves function as safety valves by relating Kleaf and the hydraulic safety margin (stem water potential minus the water potential at which 50% of conductivity is lost (Psi(stem) - Psi(50))). We also examined related plant traits including the operating range of water potentials, wood density, leaf mass per area, and leaf area to sapwood area ratio to provide insight into whole-plant water use strategies.For hydrated shoots, Kleaf was negatively correlated with KS, supporting the HSH. Additionally, Kleaf was positively correlated with the hydraulic safety margin and negatively correlated with the leaf area to sapwood area ratio.Consistent with the HSH, our data indicate that leaves may act as control valves for species with high KS, or a low safety margin. This critical role of leaves appears to contribute importantly to plant ecological specialization in a drought-prone environment.