Multiple time scale optimization explains functional trait responses to leaf water potential.

Area of Science:

• Plant physiology
• Ecology
• Mathematical modeling

Background:

• Plant water stress responses occur over short and long timescales.
• Short-term stomatal adjustments and long-term trait adaptations are typically studied independently.
• These timescales are interdependent, with long-term traits influencing short-term stomatal behavior.

Purpose of the Study:

• To optimize long-term plant traits affecting short-term stomatal responses using an economic framework.
• To analyze the resilience of xylem and nonstomatal limitations (NSLs) to photosynthesis under low water potentials.
• To understand the mathematical basis of trait coordination across different timescales.

Main Methods:

• An economic framework was employed to model trait optimization.
• Mathematical analysis was used to determine optimal trait values and their relationships.
• The study focused on xylem resilience and NSLs impacting photosynthesis.

Main Results:

• Optimal xylem resilience increases with increasing climatic aridity.
• A 2:1 linear ratio constraint was suggested between xylem 50% conductance and NSL 50% capacity points, requiring experimental verification.
• Trait coordination arises mathematically from optimizing across timescales.

Conclusions:

• Plant trait optimization under water stress is mathematically derivable.
• Xylem resilience and NSLs show coordinated responses influenced by aridity.
• The model provides a framework for understanding trait interdependence and can aid plant modeling with limited trait data.