Abstract
This study analyzes stomatal conductance (g(sc)) in Trifolium repens L., Lolium perenne L., and Triticum aestivum L. under varying environmental conditions. Light-response curves for photosynthesis (A(n)-I) at 420 μmol mol(-1) CO(2) were used to determine saturating irradiance (I(sat)) using a light-response model for photosynthesis, and CO(2)-response curves for photosynthesis (A(n)-C(i)) were measured at I(sat) and half I(sat) for these C(3) 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 (A(n)) relative to g(sc) under changing irradiance or CO(2). The BWB model overestimated g(sc) response, simplifying stomatal behavior, while the Medlyn model deviated at high A(n) values, indicating limitations in dynamic responses. The new model showed a better empirical fit under the tested conditions, achieving high R(2) values and low AIC values across all three species, and demonstrated a strong alignment with empirical data. Our findings highlight the complexity of g(sc) 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.