The ISBA (Interactions between Soil, Biosphere, and Atmosphere) scheme (Noilhan & Planton 1989, Mon. Wea. Rev., 117:536-549) is modified in order to account for the atmospheric carbon dioxide concentration on the stomatal aperture. The physiological stomatal resistance scheme proposed by Jacobs et al. (1996, Agric. For. Meteorol., 80:111-134) is employed to describe photosynthesis and its coupling with stomatal resistance at leaf level (instead of the Jarvis-type parameterization used in the standard version). A representation of the soil water stress effect is obtained by multiplying the mesophyll conductance gm of the Jacobs' model by the normalized soil moisture in the root-zone. The scaling up from the leaf to the canopy is performed by a 3-point Gauss quadrature integration according to the method proposed by Jacobs et al. (1996) and using the work of Roujean (1996, J. Geophys. Res., 101D5:9523-9532). The computed canopy net assimilation is used to feed a simple growth submodel, and to predict the density of vegetation cover: growth is described as the accumulation of net assimilation, and senescence as the result of a deficit of photosynthesis. The new scheme, called ISBA-Ags, is applied to different micrometeorological databases for which micrometeorological measurements were available over one annual cycle or more: MUREX (Bessemoulin et al. 1996), PILPS/Cabauw (Chen et al. 1997), HAPEX-MOBILHY/Caumont (Andre et al. 1986), INRA/Avignon (Olioso et al. 1996), INRA/Castanet (Cabelguenne et al. 1990), and ARME (Shuttleworth et al. 1984).