Brittleness of twig bases in the genus Salix:: fracture mechanics and ecological relevance
Brittleness of twig bases in the genus Salix:: fracture mechanics and ecological relevance
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DOI：
10.1093/jexbot/51.344.617
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发表时间：
2000-03-01
影响因子：
6.9
通讯作者：
Speck, T
中科院分区：
文献类型：
--
作者：
Beismann, H;Wilhelmi, H;Speck, T
对柳属内的树枝基部进行了研究。文献中定义的树枝基部的脆性既不与杨氏模量相关，也不与生长应变相关，对 S. alba、S. fragilis 和 S. x rubens 进行了测量。对于物种 S. alba、S. appiculata、S. eleagnos、S. fragilis、S. purpurea、S. triandra、S. viminalis 和 S. x rubens，折断树枝的断裂表面为调查并 用“相对粗糙度”（断裂表面的粗糙面积与断裂表面的整个面积之比）半定量地描述。相对粗糙度明显符合文献中给出的脆性和非脆性物种的分类。尝试通过机械测试来量化脆性。应力和应变的绝对值与由相对粗糙度定义的树枝基部的脆性无关。然而，“指数应力”（屈服应力与断裂应力之比）或“指数应变”（屈服应变与断裂应变之比）与相对粗糙度密切相关。指数应力与指数应变的图形分析揭示了一条直线，在这条直线上，八种物质根据其脆性进行排序。根据生长形式和栖息地，柳树的脆枝基部可以在生态上发挥机械安全机制的作用，此外还可以作为繁殖机制。
The twig bases within the genus Salix were investigated. Brittleness of twig bases as defined in the literature neither correlates with Young's modulus nor with growth strains, which were measured for S. alba, S. fragilis and S. x rubens, For the species S. alba, S. appendiculata, S. eleagnos, S. fragilis, S. purpurea, S. triandra, S. viminalis, and S. x rubens, fracture surfaces of broken twigs were investigated and semiquantitatively described in terms of 'relative roughness' (ratio of rough area of fracture surface over whole area of fracture surface). The relative roughness clearly corresponds with the classification into brittle and nonbrittle species given in the literature. An attempt was made to quantify brittleness with mechanical tests. The absolute values of stress and strain do not correlate with the brittleness of the twig bases as defined by the relative roughness. However, the 'index stress' (ratio of stress at yield over stress at fracture) or the 'index strain' (ratio of strain at yield over strain at fracture), correlate well with the relative roughness. The graphic analysis of index stress against index strain reveals a straight line on which the eight species are ordered according to their brittleness. Depending on growth form and habitat, brittle twig bases of willows may function ecologically as mechanical safety mechanisms and, additionally, as a propagation mechanism.