Plants are very complex systems. If agronomic plants, like rice, maize or corn, are essential to provide food or other kind of goods, trees are also essential to preserve the carbon balance, or even to absorb carbon surplus. Despite the great importance of plants, only a small number of modellers, and applied mathematicians are involved in the modelling, the development of mathematical tools, the simulation of plant growth, and, in general, in problems related to Agronomy or Forestry. In fact, the amount of knowledges necessary to understand how a plant is growing is huge and only a multidisciplinary approach can be used to overcome the encountered di_culties. Phenomena are so complex, that even botanist, agronomists and foresters still debate how to handle them e_ciently in plant growth models, and, more important, what are the essential ingredients to take into account to obtain a realistic modeling. Indeed, if we know very precisely what is going on in photosynthesis, transpiration processes,..., we didn't yet succeed in the development of macroscopic laws, like in Physics or in Mechanics. Plant growth modelling is not only challenging from the scienti_c point of view, but is also crucial for real applications, like, for instance, improving crop yields, developing biological tools against Pest attacks, studying the impact of climate change, time evolution of rain forests,.... Thus not only plant growth modeling is challenging but its interactions with the environment too. Up to now people have used di_erent modeling for plant growth, like empirical models, geometric models, process-based models or functional and structural plant models [7].... AMAP laboratory (BotAny and coMputationAl Plant architecture) is a place where Botany, Ecophysiology, Plant Architecture, Applied Mathematics, and Computer Science are deeply connected [1]. AMAP has become World leader in Botany, in Plant Architecture [3], and, based on biological knowledges, has developed several Simulatio