School of Ecosystem and Forest Sciences, The University of Melbourne, 500 Yarra Boulevard, Richmond, Victoria, 3121, Australia.
Plant Cell Environ. 2017 Aug;40(8):1500-1511. doi: 10.1111/pce.12948. Epub 2017 Apr 27.
The water potential at turgor loss point (Ψ ) has been suggested as a key functional trait for determining plant drought tolerance, because of its close relationship with stomatal closure. Ψ may indicate drought tolerance as plants, which maintain gas exchange at lower midday water potentials as soil water availability declines also have lower Ψ . We evaluated 17 species from seasonally dry habitats, representing a range of life-forms, under well-watered and drought conditions, to determine how Ψ relates to stomatal sensitivity (pre-dawn water potential at stomatal closure: Ψg ) and drought strategy (degree of isohydry or anisohydry; ΔΨ between well-watered conditions and stomatal closure). Although Ψg was related to Ψ , Ψg was better related to drought strategy (ΔΨ ). Drought avoiders (isohydric) closed stomata at water potentials higher than their Ψ ; whereas, drought tolerant (anisohydric) species maintained stomatal conductance at lower water potentials than their Ψ and were more dehydration tolerant. There was no significant relationship between Ψ and ΔΨ . While Ψ has been related to biome water availability, we found that Ψ did not relate strongly to stomatal closure or drought strategy, for either drought avoiders or tolerators. We therefore suggest caution in using Ψ to predict vulnerability to drought.
膨压丧失点水势（Ψ）被认为是决定植物耐旱性的关键功能特征，因为它与气孔关闭密切相关。由于土壤水分可用性下降时，植物能够在较低的中午水势下维持气体交换，因此Ψ可能表明植物具有耐旱性，Ψ也较低。我们在充分浇水和干旱条件下，评估了来自季节性干旱生境的 17 个物种，这些物种代表了一系列生活型，以确定Ψ与气孔敏感性（气孔关闭时的清晨前水势：Ψg）和干旱策略（等水或不等水程度；充分浇水条件和气孔关闭之间的ΔΨ）有何关系。尽管Ψg与Ψ有关，但Ψg与干旱策略（ΔΨ）的关系更好。耐旱性回避者（等水）在水势高于其Ψg时关闭气孔；而耐旱性（不等水）物种则在低于其Ψg的水势下维持气孔导度，并具有更高的耐旱性。Ψ与ΔΨ之间没有显著关系。虽然Ψ与生物群落水分可用性有关，但我们发现，对于耐旱性回避者或耐受者，Ψ与气孔关闭或干旱策略的关系并不密切。因此，我们建议在预测对干旱的脆弱性时要谨慎使用Ψ。
