title: Morphometric and mechanical characteristics of Equisetum hyemale stem enhance its vibration.
abstract: The order of the internodes, and their geometry and mechanical characteristics influence the capability of the Equisetum stem to vibrate, potentially stimulating spore liberation at the optimum stress setting along the stem. Equisetum hyemale L. plants represent a special example of cellular solid construction with mechanical stability achieved by a high second moment of area and relatively high resistance against local buckling. We proposed the hypothesis that the order of E. hyemale L. stem internodes, their geometry and mechanical characteristics influence the capability of the stem to vibrate, stimulating spore liberation at the minimum stress setting value along the stem. An analysis of apex vibration was done based on videos presenting the behavior of an Equisetum clump filmed in a wind tunnel and also as a result of excitation by bending the stem by 20°. We compared these data with the vibrations of stems of the same size but deprived of the three topmost internodes. Also, we created a finite element model (FEM), upon which we have based the 'natural' stem vibration as a copy of the real object, 'random' with reshuffled internodes and 'uniform', created as one tube with the characters averaged from all internodes. The natural internode arrangement influences the frequency and amplitude of the apex vibration, maintaining an equal stress distribution in the stem, which may influence the capability for efficient spore spreading.
authors.affiliation: Department of Forest Botany, Faculty of Forestry, Warsaw University of Life Sciences, 159 Nowoursynowska St., 02-776, Warsaw, Poland. urszula.zajaczkowska@wl.sggw.pl.
authors.forename: Urszula
authors.initials: U
authors.lastname: Zajączkowska
authors.affiliation: Department of Mechanics of Materials, Institute of Fundamental Technological Research, Polish Academy of Sciences, 5B Pawińskiego St., 02-106, Warsaw, Poland.
authors.forename: Stanisław
authors.initials: S
authors.lastname: Kucharski
authors.affiliation: Department of Mechanics of Materials, Institute of Fundamental Technological Research, Polish Academy of Sciences, 5B Pawińskiego St., 02-106, Warsaw, Poland.
authors.forename: Zdzisław
authors.initials: Z
authors.lastname: Nowak
authors.affiliation: Institute of Aeronautics and Applied Mechanics, Warsaw University of Technology, 24 Nowowiejska St., 00-665, Warsaw, Poland.
authors.forename: Kamila
authors.initials: K
authors.lastname: Grabowska
mesh_terms: D001696:Biomechanical Phenomena / Q000502:physiology; D020829:Equisetum / Q000033:anatomy & histology / Q000502:physiology*; D018547:Plant Stems / Q000033:anatomy & histology / Q000502:physiology*; D013170:Spores / Q000502:physiology; D014732:Vibration
keywords: Mechanical properties; Plant biomechanics; Segmented structure; Stem vibration; Stress distribution; Wind