The complex interaction loops between organogenesis, assimilate production and partitioning are a crucial core component of most functional-structural plant growth model; yet these three processes are seldom fully coupled and there is no consensus on how it should be done. In this context, the use of the internal trophic pressure as a regulating variable of the development processes is an option that has attracted increasing interest in recent years. Generalizing this approach is however hampered by the fact that it is a non-measurable quantity that can be only assessed through model parametric estimation, for which the methodology is not straightforward, especially when the model is stochastic. In this paper, our objectives are (i) to present a stochastic GreenLab model of plant growth (named 'GL4') with feedback effect of plant functioning, represented by the ratio of biomass supply to demand, on organogenesis, (ii) to illustrate some of the model properties on a virtual plant featuring the Roux architectural model, and (iii) to present the methodology for its parameter estimation and (iv) its application to two virtual test-cases. Such virtual fitting exercise allows a better understanding of the procedure as well as it thorough evaluation: it is therefore a prerequisite to any future application to real plants