Abstract FR:

The research presented in this thesis uses computational techniques to heighten our comprehension of shoot apical meristem (SAM) development, and in particular the process of regular organ initiation, called phyllotaxis. This work is focused on the role of an essential plant hormone, auxin, in SAM development. In this thesis, I introduce an auxin-transport model of phyllotaxis at cellular scale, which is able to reproduce spiral phyllotaxis patterns observed in vivo. The auxin-transport is mediated by special membrane carrier molecules, called PIN proteins. The polarization of PIN inside of the cell is regulated by the flux of auxin, as it was suggested in the original canalization concept proposed by Tsvi Sachs. The proposed flux-based model reproduces PIN distribution observed in vivo both, in L1 meristem layer and as well in the rib zone of the meristem. Second part of the thesis is dedicated to the simulations of growth. In this part, I introduce the physical-based framework to simulate growth of the meristem including tropisms. Since auxin modifies rigidity of cell walls leading to an increase in growth rates in the spots of its high concentration, the introduced framework is used to upgrade auxin transport-based model of phyllotaxis. In this upgraded model the transport-based patterning mechanism directly modifies the growth directions of the meristem, allowing us to study the coupling of growth, auxin and PIN distributions