Towards a model of wheat leaf morphogenesis at plant scale driven by organ-level metabolites

Leaf dimensions, specific mass and composition are traits of interest, as leaves constitute the main exchange surface with the aboveground environment. These variables arise from the interplay between many processes, and vary with growth conditions. Models of plant growth are useful tools to explore a wide range of climatic scenarios, management practices and genotypes. However, most models lacks process-based formalisms allowing simulating shoot architecture plasticity. We propose a functional-structural wheat model that couples carbon and nitrogen metabolism with leaf morphogenesis during the vegetative stage. The originality of our model relies on the interaction between leaf growth and the metabolism of carbon and nitrogen in the growing zone, which is possible thanks to an explicit and detailed formalism of the processes at organ level. The model simulates the appearance of successive leaves using coordination rules instead of a constant phyllochron as a driving mechanism. As a first step, main modules were evaluated separately: the coordination model and the metabolism model of a single growing leaf. The model shows interesting emergent properties: phyllochron stability, pattern of mature leaf length along the culm and realistic kinetics of length, dry mass and concentrations in both growing and mature zones. A qualitative evaluation strategy of the completely integrated model at plant scale is then proposed. As a conclusion, the model appears to be a useful concept, which could be transposed to other grasses.