The Stomatal Response to Temperature Is Enhanced by High Evaporative Demand, Consistent With a Partially Hydraulic...

Area of Science:

• Plant Physiology
• Plant Hydraulics
• Stomatal Physiology

Background:

• The direct response of stomata to temperature (DRST) is understudied due to experimental challenges in maintaining constant leaf-to-air vapor pressure deficit (Δw).
• Existing data suggest a positive DRST, but the underlying physiological mechanisms remain largely unknown.

Purpose of the Study:

• To investigate the role of a hydraulic mechanism in the direct response of stomata to temperature (DRST).
• To test the hypothesis that temperature-induced changes in water viscosity increase hydraulic conductance, leading to stomatal opening.
• To determine if the predicted dependence of DRST on Δw holds true across diverse angiosperm species.

Main Methods:

• Experimental measurements of DRST were conducted under controlled conditions.
• The study compared DRST at two distinct leaf-to-air vapor pressure gradients (Δw).
• Six diverse angiosperm species were utilized to assess interspecific variation.

Main Results:

• Results support the hypothesis that hydraulic mechanisms contribute to DRST.
• A significant positive DRST was observed, with considerable variation among species.
• In three of six species, the influence of Δw on DRST was substantially greater than predicted by the hydraulic theory alone.

Conclusions:

• A hydraulic mechanism, driven by temperature-dependent water viscosity, plays a role in the direct response of stomata to temperature.
• The magnitude of DRST is influenced by the leaf-to-air vapor pressure gradient (Δw).
• Additional, yet unidentified, mechanisms likely contribute to the observed enhancement of DRST by Δw in some species.