Modelling the daily course of capitulum temperature in a sunflower canopy

A model is proposed to estimate the daily course of capitulum temperature in a sunflower canopy from the beginning of flowering, when the capitulum stands above the canopy. This phase is particularly important for yield determination because it marks the beginning of seed development. The model is based on the equations describing the energy exchanges between the soil–plant system and the atmosphere. The local microclimate surrounding the capitulum is explicitly calculated. The input data are air characteristics at screen level and incident radiations. Some parameters describing canopy architecture and soil water content are also required. The output of the model, i.e., capitulum and leaf temperatures, were successfully compared to measurements made in a field experiment. Simulations have also been made to explore the effects of plant architecture on capitulum temperature. The model can be useful in numerous ecophysiological and genetic studies where thermal environment is taken into account.