A constraint-relaxation-recovery mechanism for stomatal dynamics

Area of Science:

• Plant Physiology
• Biophysical Modeling
• Computational Biology

Background:

• Existing OnGuard models offer quantitative insights into stomatal function but predict opening kinetics significantly slower than observed.
• A missing component in current models is the mechanical constraint imposed by surrounding epidermal cells on guard cell expansion.

Purpose of the Study:

• To introduce and validate a new mechanism in OnGuard2 that accounts for the constraint-relaxation-recovery dynamics of surrounding cells during stomatal opening.
• To improve the accuracy of stomatal kinetics modeling and understand the role of solute flux in this process.

Main Methods:

• Development of the OnGuard2 model incorporating a constraint-relaxation-recovery mechanism based on solute release and turgor changes in surrounding cells.
• Validation of the model against experimental data from wild-type Arabidopsis and analysis of ost2 and slac1 mutants.

Main Results:

• The OnGuard2 model with the new mechanism accurately predicts stomatal opening dynamics consistent with experimental observations.
• The model successfully predicts altered opening kinetics in ost2 H⁺-ATPase and slac1 Cl^- channel mutants.
• The results highlight a substantial and dynamic role for apoplastic solute flux in accelerating stomatal kinetics.

Conclusions:

• Incorporating the mechanical constraint of surrounding cells, implicitly through solute flux, significantly improves stomatal kinetics modeling.
• The study demonstrates the importance of solute movement in the apoplastic space for rapid stomatal responses.
• The refined model provides a more satisfactory representation of stomatal aperture dynamics.