Zajączkowska Urszula, Kucharski Stanisław, Nowak Zdzisław, Grabowska Kamila
Department of Forest Botany, Faculty of Forestry, Warsaw University of Life Sciences, 159 Nowoursynowska St., 02-776, Warsaw, Poland.
Department of Mechanics of Materials, Institute of Fundamental Technological Research, Polish Academy of Sciences, 5B Pawińskiego St., 02-106, Warsaw, Poland.
Planta. 2017 Apr;245(4):835-848. doi: 10.1007/s00425-017-2648-1. Epub 2017 Jan 7.
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.
节间的顺序、其几何形状和力学特性会影响木贼茎的振动能力，有可能在沿着茎的最佳应力设定下刺激孢子释放。木贼属植物是细胞固体结构的一个特殊例子，通过高惯性矩和相对较高的抗局部屈曲能力实现机械稳定性。我们提出了一个假设，即木贼茎节间的顺序、其几何形状和力学特性会影响茎的振动能力，在沿着茎的最小应力设定值下刺激孢子释放。基于在风洞中拍摄的木贼丛行为的视频以及通过将茎弯曲20°进行激发的结果，对顶端振动进行了分析。我们将这些数据与相同大小但去掉最上面三个节间的茎的振动进行了比较。此外，我们创建了一个有限元模型（FEM），在该模型上我们基于真实物体的“自然”茎振动、节间重新排列的“随机”振动以及作为一个从所有节间平均特征创建的“均匀”振动。自然的节间排列会影响顶端振动的频率和幅度，在茎中保持相等的应力分布，这可能会影响有效孢子传播的能力。
