THE MECHANICS OF ANCHORAGE IN SEEDLINGS OF SUNFLOWER, HELIANTHUS-ANNUUS L
THE MECHANICS OF ANCHORAGE IN SEEDLINGS OF SUNFLOWER, HELIANTHUS-ANNUUS L
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DOI：
10.1111/j.1469-8137.1989.tb04705.x
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发表时间：
1989-10-01
期刊：
影响因子：
9.4
通讯作者：
ENNOS, AR
中科院分区：
文献类型：
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作者：
ENNOS, AR
施加在植物上的力会使许多根受到张力，如果要防止连根拔起，就必须通过剪切将张力转移到土壤中。应力分布将取决于土和根的相对刚度，而破坏模式将取决于土和根-土结合的相对强度。本研究结合了用拉力试验机对向日葵根茎进行的连根拔起试验和对根系和土壤进行的力学试验。最大抽拔力随长度渐近增大，并在很低的位移时达到最大值。根毛和土壤颗粒覆盖了拔根顶端20 mm的锥形部分，而下圆柱形部分为光秃秃的。土壤比根系更硬，因此剪切应力最初集中在根系顶部，顶部20mm以上的土壤强度抵抗连根拔起。根部较低的区域后来受到压力，它们稀疏的根毛被剪掉，只能通过摩擦来抵抗连根拔起。在进一步的试验中，根的上部和下部被分开连根拔起。正如预测的那样，在单位长度上，上部区域对连根拔起的阻力要大得多，而位移也比下部区域小得多。根茎的顶部很适合锚固，它产生的丰富的根毛和粘液将根粘在土壤上。因此，较低的区域免受损害。
Forces applied to plants will subject many of the roots to tension, which must be transferred to the soil via shear if uprooting is to be prevented. The stress distribution will depend on the relative stiffnesses of the earth and root, and the mode of failure will depend on the relative strength of the soil and of the root-soil bond. This study of the anchorage of sunflower radicles combined uprooting tests performed by a tensile testing machine with mechanical tests on the roots and soil. The maximum extraction force increased with length to an asymptotic value and was reached at a very low displacement. Root hairs and soil particles covered the tapered top 20 mm of extracted root, but the lower cylindrical region was bare. The soil was stiffer than the root, so shear stress was initially concentrated at the top of the root, soil strength over the top 20 mm resisting uprooting. Lower regions of the root were stressed later, their sparser root hairs being sheared off, and resist uprooting only by friction. In a further test upper and lower regions of radicles were uprooted separately. As predicted, the upper region generated much greater resistance to uprooting per unit length, and at much lower displacements than the lower region. The top of the radicle is well adapted for anchorage, the profuse root hairs and mucigel it produces glueing the root to the soil. The lower regions are thus protected from damage.