Taking into account the 3D canopy structure to study the physical environment of plants: the Monte Carlo solution

The plants growth and development depend directly on several physical variables, such as light, temperature or humidity. Thus, solar radiation acts both as a source of energy for photosynthesis and the energy budget, and as a source of information in photomorphogenesis. Moreover, physical processes may indirectly influence the canopy development. For example the plant pathogen cycles depend on the same physical variables as for plant growth, but the spread of pathogens within the canopy depends on water motion or wind. The function-structure plant models (FSPM) describe the plant modeling at an organ scale. That approach requires then a description of the physical environment at the same scale. On the other hand, the modeling of the plants physical environment at the scale of organs requires an explicit description of the 3D canopy structure. These data are provided by FSPMs The physical plant environment is determined by the spatial distribution of physical variables q, such as light flux, a water quantity… This distribution depends on the interactions between these mass and energy and the plant organs and on the organ-to-organ transport of mass and energy within the canopy. These interactions are described by local physical laws for each plant organ. These laws quantify how an incident quantity of q increases or decreases after having interacted with an organ. In our approaches, the 3D modeling of the plants physical environment consists in an integration of local physical interaction laws over the 3D plant structure. This integration solves the transport of mass and energy to determine the spatial distribution. A formalization of this integration is described by the following equation: ) 1 ( d ) , ( ) , ( ) , , ( ) , ( ) , ( , , 0 ∫ ∫ ∈ ⋅ ⋅ + = ∈ ∀ L r r r r r r r r L r r r r r r