# Novel Model for Stomatal Conductance: Enhanced Accuracy Under Variable Irradiance and CO2 in C3 Plant Species

## TL;DR

A new model for predicting how plants control gas exchange through their stomata is more accurate than existing models under changing light and CO2 conditions.

## Contribution

A novel stomatal conductance model is proposed that outperforms existing models in predicting plant responses to environmental changes.

## Key findings

- The new model achieved high R2 and low AIC values across three C3 plant species under varying light and CO2 conditions.
- Existing models like BWB and Medlyn showed limitations in accurately describing stomatal behavior under high light or CO2 fluctuations.
- The improved model better represents stomatal dynamics, which is crucial for understanding plant resilience and productivity.

## Abstract

This study introduces a new model for predicting stomatal conductance (gsc)—the rate at which plants exchange gas such as CO2 and water vapor with the atmosphere through stomata—in three common C3 plant species. The researchers compared a new model proposed by Ye et al. with two widely used models (Ball–Woodrow–Berry and Medlyn models) under varying light intensities and CO2 conditions. The study found that the new model more accurately describes how gsc responds to changes in the environment, especially under high light or fluctuating CO2 levels. The results highlight the limitations of existing models and demonstrate the improved predictive power of the new approach. This work is important for better understanding plant water use efficiency, improving crop productivity, and predicting how plants may respond to climate change.

This study analyzes stomatal conductance (gsc) in Trifolium repens L., Lolium perenne L., and Triticum aestivum L. under varying environmental conditions. Light-response curves for photosynthesis (An–I) at 420 μmol mol−1 CO2 were used to determine saturating irradiance (Isat) using a light-response model for photosynthesis, and CO2-response curves for photosynthesis (An–Ci) were measured at Isat and half Isat for these C3 plant species. The Ball–Woodrow–Berry (BWB) model, Medlyn model, and a new model were compared for their ability to describe the net photosynthetic rate (An) relative to gsc under changing irradiance or CO2. The BWB model overestimated gsc response, simplifying stomatal behavior, while the Medlyn model deviated at high An values, indicating limitations in dynamic responses. The new model showed a better empirical fit under the tested conditions, achieving high R2 values and low AIC values across all three species, and demonstrated a strong alignment with empirical data. Our findings highlight the complexity of gsc regulation and the need for improved models to better represent stomatal dynamics under different environmental conditions. This research is vital for optimizing water use efficiency, enhancing crop productivity, and understanding plant resilience to climate change.