A Modeling Approach to Stomatal Conductance under Different Vapor Pressure Conditions

Stomatal conductance, determined by the stomatal aperture of leaves, governs gas exchange between plants and the atmosphere. This mechanism is closely related to photosynthesis and the ability of plants to adapt to environmental changes, including those caused by global warming. This study proposes a two-dimensional nonlinear model based on ordinary differential equations to estimate stomatal conductance over time. The model integrates key environmental drivers, air temperature and relative humidity, through the vapor pressure deficit, and couples stomatal conductance with leaf water content. A modified Gompertz-type equation provides a nonlinear structure capable, in principle, of representing delayed and potentially asymmetric stomatal adjustment toward a dynamic steady-state target. We perform both local and global sensitivity analyses to assess parameter influence, revealing vapor pressure deficit as the most influential factor affecting equilibrium stomatal conductance. The findings indicate that the model reproduces the main trend of stomatal conductance in the preliminary hold-out evaluation, while further validation with independent datasets remains necessary.