On the Strength of Herbaceous Vascular Plant Stems

During the past 120 years researchers have tried to provide an understanding of the relationship between the arrangement of stiffening tissue in the cross-section of plant stems and their mechanical integrity. The mechanical analysis of vertical stems of self-supporting plants has traditionally been concerned with issues involving global and local stability of the stem, and with stresses developed due to wind loads. Plant stem tissue, considered as a material, is both heterogeneous and highly anisotropic, and this must be reflected in any characterization of its mechanical behaviour. This fact strongly influences the type of failure criterion which should be applied for compressive failure of the stem subjected to loads causing bending. It is shown, here, that applying modern ideas as to the appropriate criteria for compressive failure of fibre-reinforced composite materials can influence how we assess the efficacy of various stelar arrangements concerning their ability to fulfill their mechanical function. Specifically, it is demonstrated that peripheral arrangements of supporting tissue are, in some circumstances, less advantageous than more uniform distributions of this tissue.