Carbon-water balance and patchy stomatal conductance

Area of Science:

• Plant Physiology
• Ecology
• Biophysics

Background:

• Stomata regulate crucial plant processes: photosynthesis (A) and transpiration (E).
• The impact of non-uniform (patchy) stomatal conductance on carbon-water balance is not fully understood.
• Previous models suggested uniform stomatal conductance is optimal for maximizing carbon gain.

Purpose of the Study:

• To investigate how patchy stomatal conductance affects plant carbon-water balance.
• To determine if patchiness is detrimental or potentially beneficial under specific environmental conditions.
• To re-evaluate the concept of 'optimal' stomatal behavior in plant gas exchange.

Main Methods:

• Mathematical modeling to analyze stomatal conductance patterns.
• Computer simulations to explore carbon gain and water-use efficiency.
• Comparison of theoretical findings with existing observational data on stomatal patchiness.

Main Results:

• The assumption of uniformly negative curvature in A-E relationships, required for uniform stomatal conductance optimality, is not always met.
• Under conditions violating this assumption, stomatal patchiness has minimal negative impact on water-use efficiency (A/E) and can even enhance it.
• Stomatal patchiness is frequently observed under the very environmental conditions where it is less detrimental or beneficial.

Conclusions:

• Patchy stomatal conductance may not significantly impair carbon-water balance in many natural scenarios.
• The definition of optimal stomatal regulation needs refinement, especially under conditions with positive curvature in A-E relationships.
• Recent observations of common, yet unobserved, stomatal patchiness align with these findings, suggesting it may be a widespread and functionally relevant phenomenon.