A systematic study of plant growth modeling is a real challenge for researchers and scientists because multidisciplinary aspects have to be integrated. Through a mathematical formalism, a plant functional-structural model needs to be developed based on knowledge from botany, agronomy, forestry, eco-physiology and computer sciences. Specialists in each discipline have proposed variety models, but most of these models are limited within their own field. It is well recognized that the malfunctioning and the limitations of these models are due to their mono-disciplinary aspects applied. A dialog between the various scientific domains involved in plant modeling is not obvious. It needs to choose, simplify and adapt the relevant knowledge from each other that is necessary and sufficient to build a plant functional-structural model. This needs also to define a right level of observations. Each notion is simplify, but the interactions between them give new theoretical results and applications. Several questions are discussed in this work. How botany gives keys to organize the multi-level information inside the plant topological structure and eventually speed up the growth computing? What kind of mathematical formalism is needed to introduce powerful tools of automatic control into plant modelling? The goal of this paper is to propose simple choices, from both biological and mathematical viewpoints, and adapt them to build an efficient dynamical model. With this model, it is possible to insure optimisation and control that are needed in agronomy.