Finite element modeling of external and internal stresses generated in the sunflower's (Helianthus annuus L.) stem after flexure

摘要

Stem flexural bending in sunflower seedlings produces important developmental modifications such as stem shortening and early flowering retardation. In this work, it is hypothesized that for the rapid long distance intra plant signaling transport of the mechanically induced stimulus towards main centers of cellular activity, stem bending generates a significant mechanical stress at vascular level. A numerical model of the young sunflower stem under static lateral action was studied. Based on its external dimensions and distribution of its constitutive tissues, a 3D finite element model of the stem was built and appropriately meshed. Stresses and strains generated in the surface and inside the stem were calculated. The FE analysis was made using the Linear Static Stress Analysis modulus of the software ALGOR. Bending due to lateral wind load was simulated by the analogous effect of prescribed displacements with magnitudes adopted from experimental results. The mechanical behavior of the stem model depends on its global shape and internal structure and is also characterized by the mechanical properties of the stem's constitutive materials as density, Young's modulus and Poisson's ratio. Lateral displacements were associated with a significant high bending stress located at the epidermis and vascular tissue. These observations could help to explain why a mechanical perturbation is highly effective to induce physiological and growth changes at early stages of plant development.