STOMATAL BEHAVIOR AND PHOTOSYNTHETIC RATE OF UNSTRESSED GRAPEVINES INSEMIARID CONDITIONS

This paper explores the possibility to use a model for assimilation ra te, A(n), to calculate stomatal conductance, g(s). The relation betwee n stomatal conductance, g(s), and net photosynthetic rate, A(n), is st udied for grapevine (Vitis Vinifera L. cv Airen). Data were collected in a dry Mediterranean vineyard in Central Spain, under a wide range o f temperature and humidity conditions, but with sufficient water suppl y. The data confirm the existence of a strong correlation between A(n) and g(s). However, the relation is strongly influenced by leaf-to-air specific humidity deficit, D-s. This influence can be expressed by me ans of a linear relation between D-s and the ratio f, which is the rat io of internal to external CO2 concentration, C-i/C-s, corrected for C O2 concentration. The data were used to tune a coupled A(n)-g(s) model using as much standard coefficients as possible. Using the linear rel ation between D-s and f, the model also takes stomatal humidity respon ses into account. A model test reveals that the current approach is ab le to simulate the photosynthetic rate and stomatal conductance of gra pevines reasonably well.