Introduction - Organ development and meristem fate is partly determined by endogenous signals moving within plants. These signals (e.g. hormones, sugar…) originate from organs considered as sources (roots, leaves, seeds…) and act on meristems to trigger developmental processes such as transition toward flowering. Functional structural plant model (FSPM) are of major interest as they are based on an explicit description of plant architecture needed for simulating transports within plants. Transport or fluxes have been modeled in FSPM with a special consideration on carbon allocation (Génard et al., 2008). Approaches for simulating hormone fluxes are scarce, adapted to plant with simple architecture and usually associated with a comprehensive knowledge on the processes to be simulated (Prusinkiewicz et al., 2009); thus limiting their adaptability in various contexts. In this study, we present a generic model for simulating signal fluxes and their impact on meristem fates in complex 3D tree structure. We applied this model to the simulation of within tree variability of floral induction in the apple tree, as a first case of study. Previous experiments (Belhassine et al., 2019) showed that floral induction in meristems occurs less often in the presence of fruit whereas it is favoured by the presence of leaves. Furthermore, the influences of fruit and leaves on the floral induction of meristems depend on the distances of those organs within the tree structure. Fruit and leaves were thus assumed to be sources of inhibiting signals (possibly gibberellins from seeds) and activating signals (possibly FT protein), respectively. However, the distance at which these signals move within the structure and the relative sensitivity of the meristems to these signals are highly difficult to estimate from experimental studies, only. Material and methods - The model uses libraries from the OpenAlea platform (Pradal et al., 2008). The model runs on 3D tree architectures coded in Multisc