Modeling bi-directional signals in complex branching structure: Application to the control of floral induction in apple trees

Flowering is a key process that determines yield in fruit trees, and a negative relationship between crop load and floral induction has been observed in many species. In apple tree, hormonal signals coming from seeds, which are assumed to be transported within the tree, are suspected to inhibit floral induction. To analyze the intertwined effects of tree architecture, crop load and inhibitory signal on floral induction we developed a generic model based on the L-system formalism. The model simulates both the basipetal and acropetal flux of the signal as well as its partitioning at each branching point and between successive metamers. First simulations on apple tree, using architectures generated by the MappleT model, showed that the model was able to reproduce well-known results of the literature, such as the variability in floral induction rate according to shoot length and type, and to reproduce experimental observations of the impact of crop load on floral induction. Moreover, the model also has the ability to simulate contrasted behavior in term of flowering patterns at the branch scale that could be related to genotypic characteristics. Although new experiments are needed to fully calibrate the model, it gives insights into interactions between plant development, architecture and floral induction that could be useful in the future for plant breeders and growers to adjust thinning intensity.