Optimization model, Stomatal conductance, Photosynthetic carboxylation capacity, Drought, Water use efficiency, Agriculture (General), S1-972, Agricultural industries, HD9000-9495

Leaf stomatal regulation of water-carbon exchange processes plays a crucial role in the water-carbon cycle. Uncovering the response mechanism of leaf gas exchange to soil water stress is challenging due to the complex effects of both the stomatal regulation (i.e., stomatal conductance, gs) and non-stomatal regulation (i.e., photosynthetic carboxylation capacity, Vcmax25). Different from previous studies that achieved stomatal and non-stomatal regulation in stomatal optimization models by linearly simplifying or independently optimizing Vcmax25, this study hypothesizes that Vcmax25 and gs are co-regulated by balancing intercellular CO₂ concentration (Ci). By adjusting stomatal opening to minimize water-carbon cost, a stomatal optimization model (SRSC model) that integrates the synergistic regulation of gs and Vcmax25 was developed. Experimental and numerical results show that the SRSC model accurately reproduces the stomatal response to environmental changes, especially for the low soil water potential conditions (Ψsoil