Contributions to the Biomechanics of Plants. I. Stabilities of Plant Stems with Strengthening Elements of Different Cross‐Sections Against Weight and Wind Forces*

Abstract

Abstract Biophysical considerations allow estimates of the mechanical stresses on self‐bearing vertical stems of plants. Even at moderate wind velocities the stresses induced by aerodynamic forces dominate over those induced by the own weight. Using polar coordinates, analytical expressions of cross‐sectional area and axial second moment of area for centrisymmetric structures with symmetries threefold or higher are derived. Calculating the relative section modulus for various (centrisymmetric) arrangements of stabilizing structures leads to an estimate of the “mechanical effectivity” of these structures. If for plant stems, seen as composite materials, the second moments of area and the elastic moduli are known, the contribution of the different tissues to mechanical stability can be determined quantitatively. The mechanical design of early “vascular” land plants and of stems of (fossil) trees and lianas in different ontogenetic stages can be assessed.