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Stomata Tape-Peel: An Improved Method for Guard Cell Sample Preparation
Published on: July 15, 2018
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Cell wall water shields stomata against falling leaf airspace humidity
Michael R Blatt1, Adrian Hills1, Tracy Lawson2
1Laboratory of Plant Physiology and Biophysics, Bower Building, University of Glasgow, Glasgow, G12 8QQ, UK.
The New Phytologist
|February 9, 2026
Summary
Plant stomata remain open even in low humidity environments, indicating cell wall water shields them. This water flux from cell walls to the substomatal cavity is crucial for regulating transpiration.
Area of Science:
- Plant Physiology
- Plant Water Relations
- Plant Anatomy
Background:
- Transpiration is the process of water movement through a plant and its evaporation from aerial parts, such as leaves, stems and flowers.
- Stomatal pores are crucial for gas exchange and transpiration, but their function under varying substomatal relative humidity (RH) is debated.
- Guard cells' water potential regulation in response to substomatal RH is not fully understood.
Purpose of the Study:
- To investigate the impact of substomatal relative humidity (RH) on stomatal conductance (gs) and guard cell water potential.
- To determine the role of cell wall hydration in maintaining stomatal opening under low RH conditions.
- To explore the kinetics of evaporative flux within the leaf.
Main Methods:
- Development of a specialized gas exchange chamber to precisely control RH and CO2 at the inner epidermal surface.
- Concurrent measurements of stomatal conductance (gs) and bulk cell wall water potential in *Vicia faba* L.
- Comparison of experimental findings with predictions from the OnGuard model.
Main Results:
- Stomata remained open with high stomatal conductance (gs) even when internal RH was significantly reduced below saturation.
- No significant decline in bulk cell wall water potential was observed until the tissue dried, causing stomatal closure and gs collapse.
- Experimental results align with OnGuard model predictions of decreased RH within the leaf under water stress.
Conclusions:
- Cell wall water plays a vital role in shielding stomata from low leaf airspace humidity, maintaining stomatal opening.
- A steady-state flux exists from liquid water in the cell wall to water vapor in the substomatal cavity and across the stomatal pore.
- The findings challenge existing models by highlighting the importance of cell wall water kinetics in regulating stomatal transpiration.
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