The dynamics of leaf and axes orientation in wheat

oral communication abstract; Context and aims: The 3D structure of plants is an important aspect of plant-interface with the environment, involved in the capture of resources, the exposition to stresses and physical transfers both within the plant and at canopy level. For these reasons describing plants in 3D is an important aspect of functional structural plant modelling. Despite of this, the representation of plants in FSPM pays little attention to the dynamic aspects of geometry. This work analyses how the 3D geometry of wheat leaves and axes changes from plant emergence to maturity. Methods: Experiments were conducted on three commercial winter wheat cultivars of contrasted stature (erectophile and planophile). Plants were grown in compartments installed outdoor at population densities of 70p/m² and 200p/m². Sixteen plants per treatment were tagged and we recorded weekly the number of emerged leaves on the main stem, their status (green or senescent) and digitalized the main stem leaves and all axes with a Polhemus digitizer. Results: Both main stems and tillers axes started their extension nearly horizontal and straightening progressively to reach a vertical direction only close to the time of flag leaf ligulation. The dynamic of leaf curvature depended on leaf position: lower and higher leaves showed a progressive droop down with rates and range gradually changing with leaf position and varying between genotypes, intermediate leaves showed a complex pattern with a transient straightening due to the movement of the bearing axe during their elongation. Conclusion: Our work brings a comprehensive view of leaf and axes movements and highlights the gradual straightening of the stems that is of high importance to understand leaf position and orientation. We plan to derive parameterizations for the movements observed and to evaluate with 3D models their implication in terms of light capture. We expect from that work to improve the simulations of plant-environment interactions.