Grasses exploit geometry to achieve improved guard cell dynamics.

Area of Science:

• Plant biology
• Biophysics
• Mechanobiology

Background:

• Stomata are vital pores regulating plant gas exchange.
• Grass stomata feature specialized subsidiary cells (SCs) and unique dumbbell-shaped guard cells (GCs).
• The contribution of this geometry to stomatal function is not fully understood.

Purpose of the Study:

• To investigate the mechanical role of SCs and GC geometry in grass stomatal function.
• To elucidate the mechanisms underlying improved stomatal performance in grasses.

Main Methods:

• Development of a finite element method (FEM) model of the grass stomatal complex.
• In silico simulations and experimental mutant analyses were performed.

Main Results:

• The FEM model accurately replicated observed stomatal pore opening and closure.
• A reciprocal pressure system between GCs and SCs is crucial for function, with SCs acting as restraining springs.
• SCs are beneficial but not essential for stomatal function, enhancing system responsiveness.
• GC wall anisotropy is not required; a thick GC rod region is important for pore opening.

Conclusions:

• Specific cellular geometry and mechanical properties are essential for effective grass stomatal function.
• Subsidiary cells significantly enhance the responsiveness of the stomatal complex.