Hawkesbury Institute for the Environment, University of Western Sydney, Penrith, New South Wales, Australia.
School of Biological Science, University of Tasmania, Hobart, Tasmania, Australia.
Plant Cell Environ. 2018 Dec;41(12):2869-2881. doi: 10.1111/pce.13418. Epub 2018 Sep 14.
The ability to resist hydraulic dysfunction in leaves, stems, and roots strongly influences whether plants survive and recover from drought. However, the coordination of hydraulic function among different organs within species and their links to gas exchange during drought and recovery remains understudied. Here, we examine the interaction between gas exchange and hydraulic function in the leaves, stems, and roots of three semiarid evergreen species exposed to a cycle of severe water stress (associated with substantial cavitation) and recovery. In all species, stomatal closure occurred at water potentials well before 50% loss of stem hydraulic conductance, while in two species, leaves and/or roots were more vulnerable than stems. Following soil rewetting, leaf-level photosynthesis (A ) returned to prestress levels within 2-4 weeks, whereas stomatal conductance and canopy transpiration were slower to recover. The recovery of A was decoupled from the recovery of leaf, stem, and root hydraulics, which remained impaired throughout the recovery period. Our results suggest that in addition to high embolism resistance, early stomatal closure and hydraulic vulnerability segmentation confers drought tolerance in these arid zone species. The lack of substantial embolism refilling within all major organs suggests that vulnerability of the vascular system to drought-induced dysfunction is a defining trait for predicting postdrought recovery.
叶片、茎和根抵抗水力功能障碍的能力强烈影响植物能否在干旱中存活并恢复。然而，物种内不同器官水力功能的协调及其与干旱和恢复过程中气体交换的联系仍研究不足。在这里，我们研究了在经历严重水分胁迫（与大量空化相关）和恢复循环的三种半干旱常绿物种的叶片、茎和根中的气体交换和水力功能之间的相互作用。在所有物种中，气孔关闭发生在茎水力导度损失 50%之前的水势，而在两个物种中，叶片和/或根比茎更脆弱。土壤重新润湿后，叶片水平的光合作用 (A) 在 2-4 周内恢复到胁迫前水平，而气孔导度和冠层蒸腾作用恢复较慢。A 的恢复与叶片、茎和根水力功能的恢复脱钩，在整个恢复期间，叶片、茎和根水力功能仍受损。我们的结果表明，除了高栓塞抗性外，早期气孔关闭和水力脆弱性分段赋予了这些干旱带物种耐旱性。所有主要器官中都没有大量栓塞再填充，这表明血管系统对干旱引起的功能障碍的脆弱性是预测干旱后恢复的决定性特征。
