Dependence of stomatal conductance on leaf chlorophyll concentration and meteorological variables

We examined the dependence of stomatal conductance on physiological properties and meteorological variables using a Jarvis-type stomatal conductance model that included a function representing leaf chlorophyll concentration as a physiological property. We sampled the leaves of 5- and 10-year-old Quercus serrata trees. A low leaf chlorophyll concentration imposed a restriction on the opening capacity of the stomata. The stomatal conductance variability depended markedly on chlorophyll function; the degree of dependence was almost equal to that on solar radiation or vapour pressure deficit. The characteristics of stomatal conductance response to meteorological or physiological changes exhibited little seasonal variation (except relative to temperature). Stomatal conductance variability depended on the following meteorological parameters in decreasing order: radiation, vapour pressure deficit, leaf temperature, and soil moisture; this order did not vary seasonally. The dependence of stomatal conductance variability on the seasonal change in chlorophyll concentration was larger in spring and autumn than in summer. These results indicate that the consideration of seasonal changes in plant physiological properties is important in evaluating the water, energy, and CO2 cycles between plants and the atmosphere.