An Individual Based Model of Wound Closure in Plant Stems

Wound closure in plant stems (after either fire or mechanical damage) is a complex, multi-scale process that involves the formation of a callous tissue (callus lips) responsible for cell proliferation and overgrowth at the injury edges, resulting in coverage of the scarred tissue. Investigating such phenomena, it is difficult to discriminate between cell-specific growth responses, associated with physiological adaptations, and cell proliferation reactions emerging from specific cambium dynamics due to changes in mechanical constrains. In particular, the effects of cell-cell mechanical interactions on the wound closure process have never been investigated. To understand to what extent callus lip formation depends on the intra-tissue mechanical balance of forces, we built a simplified individual-based model (IBM) of cell division and differentiation in a generic woody tissue. Despite its simplified physiological assumptions, the model was capable to simulate callus hyperproliferation and wound healing as an emergent property of the mechanical interactions between individual cells. The model output suggests that the existence of a scar alone does constrain the growth trajectories of the remaining proliferating cells around the injury, thus resulting in the wound closure, ultimately engulfing the damaged tissue in the growing stem.