Incorporating cultivar-specific stomatal traits into stomatal conductance models improves the estimation of evapotranspiration enhancing greenhouse climate management

The effect of considering cultivar differences in stomatal conductance (g_s) on relative air humidity (RH)-related energy demand was addressed. We conducted six experiments in order to study the variation in evapotranspiration (ET_c) of six pot rose cultivars, investigate the underlying processes and parameterise a g_s-based ET_c model. Several levels of crop ET_c were realised by adjusting the growth environment. The commonly applied Ball–Woodrow–Berry g_s-sub-model (BWB-model) in ET_c models was validated under greenhouse conditions, and showed a close agreement between simulated and measured ET_c. The validated model was incorporated into a greenhouse simulator. A scenario simulation study showed that selecting low-g_s cultivars reduces energy demand (≤5.75%), depending on the RH set point. However, the BWB-model showed poor prediction quality at RH lower than 60% and a good fit at higher RH. Therefore, an attempt was made to improve model prediction: the in situ-obtained data were employed to adapt and extend either the BWB-model, or the Liu-extension with substrate water potential (Ψ; BWB-Liu-model). Both models were extended with stomatal density (D_s) or pore area. Although the modified BWB-Liu-model (considering D_s) allowed higher accuracy (R² = 0.59), as compared to the basic version (R² = 0.31), the typical lack of Ψ prediction in greenhouse models may be problematic for implementation into real-time climate control. The current study lays the basis for the development of cultivar specific cultivation strategies as well as improving the g_s sub-model for dynamic climate conditions under low RH using model-based control systems.