The interpretation of thermal infrared (TIR) information as a crop water status indicator implies the understanding of plant water functioning in given environmental conditions. As water exchanges between plant and the atmosphere occur at leaf level through stomata, it appears interesting to work at this level to consider ecophysiological mechanisms involved in water transfer and thermal response. Also, in this study, we chose to use the 3D model of plant water balance of Dauzat [1] to interpret cotton plants temperature in terms of water status. This model is actually based on the description of plants at organ level in 3D mock-ups delivered by the AMAPmod Software [2]. Each leaf constitutive of a considered mock-up is the support of radiative and energy balance computations, directly dependant on its stomatal response to the environment, and leading to the simulation of transpiration and surface temperature. An experiment was organized between June and September 1999 in Montpellier, France, to test the model in this way. The model now appears as a useful tool to estimate, understand plant water status from TIR signal.