Aims

Root tensile tests are often rejected if failure location is outside the middle section of samples. This study aims to identify where and why failure occurs along a root axis, and hence to revisit current approaches to test-validity.

Methods

Roots from Festuca arundinacea; Lolium multiflorum; Lolium perenne were sampled from field-grown plants. Roots were tensile tested using a universal testing machine. Root samples were randomly allocated into two groups for testing. Group 1 roots were orientated with the older tissue closest to the top clamp, group 2 roots were orientated oppositely. Tensile strength, Young’s modulus and failure location were recorded for each sample.

Results

Lolium multiflorum roots were thinner and stronger than roots of Festuca arundinacea. Failure location in tensile tests depended significantly on tissue age with 75% of samples failing in the younger third of root tissue regardless of the root orientation in the testing frame. Only 7% of roots failed in the middle third of the sample.

Conclusions

Fibrous roots tested in tension were observed to consistently fail in the younger tissue along the root axis. Exclusion of samples which fail outside the middle region of the root axis needs re-evaluation for a range of species.

中文翻译：

---

根龄影响机械测试过程中草种的失败位置

目的

如果失效位置在样品的中间部分之外，则经常拒绝进行根部拉伸试验。这项研究旨在确定沿根轴出现故障的位置和原因，从而重新审视当前的测试有效性方法。

方法

苦木属的根；黑麦草 多年生黑麦草从田间种植的植物中取样。使用通用测试机对根进行拉伸测试。根样品被随机分为两组进行测试。第一组的根与最靠近顶部钳的较老组织定向，第二组的根相反。记录每个样品的拉伸强度，杨氏模量和破坏位置。

结果

多花黑麦草的根比Festuca arundinacea的根更薄更强。拉伸测试中的失效位置在很大程度上取决于组织的年龄，无论测试框架中的根部方向如何，有75％的样品在较年轻的根部组织中失效1/3。在样本的中间三分之一中，只有7％的根失败。

结论

观察到在张力下测试的纤维状根在沿着根轴的年轻组织中始终失败。排除在根轴中间区域之外失败的样本需要对一系列物种进行重新评估。