Simulation of Morphogenetical Gradients Using a Minimal Functional-Structural Plant Model (FSPM)

Context: Architectural studies highlight recurrent morphogenetical gradients that are observed on some tree species. These morphogenetical gradients are linked to morphological trends among successive shoots throughout plant structure and ontogeny. This study aims at testing a potential origin of these gradients as the complex result of some core plant functions. It will be achieved through a minimalist mathematical modelling approach. Methods: DRAFt is a discrete modelling approach at yearly step that benefits from a system of few mechanistic equations which attempts to simultaneously describe tree development (primary and secondary growth and branching) and functioning (assimilation and carbon partitioning). This FSPM aims at deeply interlacing both tree development and functioning using a formulation that keeps accuracy with knowledge about trees. DRAFt was implemented in AmapStudio for 3D simulations and outputs extractions. Main results: DRAFt succeeds in providing realistic trends with respect to morphogenetical gradients (tree base effect and axes drift). Different tree forms were simulated driven by input parameter values variations, which emphasize an effective model sensitivity. DRAFt consists in a 6 parameters system of equations which is minimalist compared to other previous more complex mechanistic FSPM. Conclusion and perspectives: This results are consistent with the idea that some morphological gradients are an emergence of few basic tree functions. Based on this generalist and simple core, some other biological processes may be plugged (apex mortality, sexuality position) depending on the accuracy to the biological question that is assessed. The minimalist formulation provides a mathematical framework that facilitates both further mathematical and computational studies. Moreover it would be interesting to be able to fit DRAFt parameters with real measurements and to carry on a meticulous sensitivity analysis of DRAFt behaviour.