Measurement of guard cell wall elasticity and implications for stomatal sensitivity to environmental stimuli

Abstract

Over the course of stomatal opening guard cells exhibit dramatic changes in volume. This dynamic characteristic is driven by changes in guard cell osmotic pressure and water potential, but constrained by the elastic properties of the guard cell walls. Thus guard cell wall elasticity will strongly influence the sensitivity of stomata to environmental stimuli. However, our understanding of guard cell wall elastic properties is limited. In this study we calculated the elastic modulus e of guard cells of Vicia faba L. by taking concurrent measurements of guard cell volume and pressure using confocal microscopy and a cell pressure probe. While controlling guard cell pressure at intervals over the range 0.3 to 5.0 MPa, guard cell volume increased with pressure in a saturating fashion and e increased linearly from approximately 2 to 40 MPa. These new data allow a quantitative understanding of the relationship between guard cell osmotic content and stomatal conductance, with implications for stomatal responses to light, CO2 and humidity.