弯曲过程中竹材薄壁细胞的形态变化

Parenchyma Cell Morphological Changes of Bamboo under Bending

【目的】从微观层面探索竹材的弯曲性能,观察细胞在弯曲过程中的形态变化,为竹材弯曲机制的研究和开发利用提供依据。【方法】以竹篾为研究对象,采用循环加载-卸载方式,在电镜下观察弯曲过程中竹篾拉伸层薄壁细胞的形态变化。通过分析循环加载过程中细胞长轴和短轴的变化、拉伸层薄壁组织的应变变化、拉伸层薄壁细胞长轴和短轴的应变变化以及拉伸层薄壁细胞回弹率的变化,比较不同加载状态下薄壁细胞的变形。【结果】竹篾弯曲过程中,随着载荷增加,在试样未被破坏前,受拉层薄壁细胞在水平方向上被拉伸,在短轴方向上有轻微压缩。同一循环周期下,卸载后薄壁细胞的长轴和短轴均发生回弹。当试样弯曲变形时,相邻薄壁细胞的细胞壁产生褶皱变形。在试样破坏前,薄壁细胞长轴和短轴发生的最大应变分别为1.03%和0.71%,薄壁组织长轴发生的最大应变为0.72%,薄壁细胞长轴和短轴的回弹率分别为30.96%和5.93%。【结论】采用Image-Pro Plus软件对细胞进行分析,可直接观察细胞变形。在弯曲过程中,竹篾拉伸层薄壁细胞长轴变长,短轴变短。加载到相同位置时,竹篾受拉层薄壁细胞在长轴方向上的应变大于短轴,长轴的回弹率比短轴高,薄壁细胞长轴方向的弹性较好。

【Objective】The excellent flexibility of bamboo is due to its microstructure.Having a deeper understanding of the flexibility of bamboo from the micro-level and exploring the morphological changes of bamboo under bending is of important significance.It might provide some bases for the bamboo bending mechanisms and its utilization.【Method】Bamboo strips were taken as the research object.The morphological changes of parenchyma cell in the tensile layer were observed by scanning electron microscope(SEM)during cycle loading.For this purpose,parenchyma cell deformation,stress-strain curves of parenchyma cell and parenchymatous tissue,as well as the changes of the cell recovery were analyzed.The deformation of parenchyma cells among different portions was also evaluated.【Result】With the increase of the load,parenchyma cell in the tensile layer was stretched in the longitudinal direction,wherea the cell was slightly compressed in the radial direction.The parenchyma cell recovered after unloading.Crease occurred among the parenchyma cells when the bamboo strip was bending.The maximal length strain and width strain of parenchyma cell reached 1.03%and 0.71%,respectively.At the same portion,the length and width recovery of parenchyma cell was 30.96%and 5.93%,respectively.The maximum length strain of parenchymatous tissue was 0.72%.【Conclusion】Image-Pro Plus could be used to analyze the cell morphology and observe the deformation directly.Parenchyma cell in the tensile layer was stretched in the longitudinal direction and compressed in the radial direction,respectively.The strain and recovery of parenchyma cell were both larger in the longitudinal direction than those in the radial direction.The parenchyma had a better elasticity in the longitudinal direction.