Radiative models for architectural modeling

Light microclimate determines many aspects of plant growth. Introducing the light-vegetation interactions into a plant model requires a radiative mode l computing fluxes at the spatial scale described in the plant model. The t hree-dimensional (3D) architectural models describe plants functionally and geometrically as sets of interconnected organs. As the geometry of each or gan is defined, the 3D canopy structure is explicitly described. These mode ls require calculation of the distribution of light energy on the 3D plant structure, to integrate physiological processes from organ to plant level. This has motivated the development of new radiative models. We introduce fi rst the principles governing the physical interactions between light and a plant canopy. We present then operational models. Fast methods have been de veloped for calculating sun and sky light directly intercepted by plant org ans. Such methods may be used for the simulation of processes depending on the UV or PAR radiations. Models taking into account the multiple scatterin g between plant elements are based either on Monte Carlo ray tracing or on the radiosity method. We present the principle of these approaches and rece nt developments on their applications to crop modelling. ((C) Inra/Elsevier , Paris.).