Rising global temperatures and vapor pressure deficits (VPD) are increasing plant water demand and becoming major drivers of large-scale plant mortality. Controlling transient leaf water loss after stomatal closure (gmin) is recognized as a key trait determining how long plants survive during soil drought. Yet, substantial uncertainty remains regarding how gmin responds to elevated temperatures and VPD and the underlying mechanisms. We measured gmin in 24 Quercus species from temperate and Mediterranean climates to determine if gmin was sensitive to a coupled temperature and VPD increase. We also explored mechanistic links to phenology, climate, evolutionary history, and leaf anatomy. We found that gmin in all species exhibited a non-linear negative temperature and VPD dependence. At 25°C (VPD = 2.2 kPa), gmin varied from 1.19 to 8.09 mmol m-2 s-1 across species but converged to 0.57 ± 0.06 mmol m-2 s-1 at 45°C (VPD = 6.6 kPa). In a subset of species, the effect of temperature and VPD on gmin was reversible and linked to the degree of stomatal closure, which was greater at 45°C than at 25°C. Our results show that gmin is dependent on temperature and VPD, is highly conserved in Quercus species, and is linked to leaf anatomy and stomatal behavior.

中文翻译：

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在高温和蒸气压不足的情况下，栎属气孔关闭作为最小叶导率的驱动因素下降


全球气温上升和蒸气压不足 （VPD） 正在增加植物的用水需求，并成为大规模植物死亡的主要驱动因素。控制气孔关闭后叶片的瞬时水分流失 （gmin） 被认为是决定植物在土壤干旱期间存活时间的关键特性。然而，关于 gmin 如何响应高温和 VPD 以及潜在机制仍然存在很大的不确定性。我们测量了来自温带和地中海气候的 24 种栎属物种的 gmin，以确定 gmin 是否对耦合温度和 VPD 增加敏感。我们还探讨了与物候学、气候、进化历史和叶子解剖学的机制联系。我们发现所有物种中的 gmin 都表现出非线性的负温度和 VPD 依赖性。在 25°C （VPD = 2.2 kPa） 时，不同物种的 gmin 在 1.19 至 8.09 mmol m-2 s-1 之间变化，但在 45°C 时收敛至 0.57 ± 0.06 mmol m-2 s-1 （VPD = 6.6 kPa）。在物种亚群中，温度和 VPD 对 gmin 的影响是可逆的，并且与气孔关闭程度有关，45°C 时气孔关闭程度大于 25°C 时。 我们的结果表明，gmin 依赖于温度和 VPD，在 Quercus 物种中高度保守，并且与叶片解剖学和气孔行为有关。