AFM技术观察慈竹纤维和薄壁细胞断面微纤丝聚集体特征

Cellulose Microfibril Aggregates in Cross-Section of Bamboo Fiber and Parenchyma Cell Wall with Atomic Force Microscopy

【目的】利用原子力显微镜(AFM)研究竹材纤维细胞和薄壁细胞纤维素微纤丝聚集体的分布规律,为竹纤维及竹材的加工利用提供理论支持。【方法】通过对脱木素处理的竹材进行树脂包埋及钻石刀修块抛光,制备出可以在AFM下进行表征的样品,利用AFM的Tapping模式对竹材纤维细胞和薄壁细胞中纤维素微纤丝聚集体进行观察。【结果】通过AFM对处理的样品进行定位扫描可以得到高度图和相图,一个维管束内不同位置纤维细胞的高度图和相图都显示出多层结构,且细胞壁层数及各壁层厚度因细胞在竹材中所处位置不同而改变;一个维管束内不同位置细胞壁的相图显示高亮度的物质分布密度不同,从细胞壁内侧到细胞壁外侧都呈不均匀分布,且各壁层相邻的位置处高亮度的物质比较密集;一个竹纤维细胞壁的相图中显示各层高亮度物质大小差异不大,而一个竹薄壁细胞壁中各层高亮度物质差异比较大。【结论】利用AFM的Tapping模式对竹材细胞壁进行观察,需要对样品进行适当处理,不仅操作相对同分辨率的手段简单,而且还可以进行定位观察,除了能够获得传统手段得到的细胞壁多壁层结构外,还能获得纤维素微纤丝聚集体的分布,是一种便捷、有效的手段;竹纤维细胞和竹薄壁细胞中纤维素微纤丝聚集体在其胞壁的横截面上都呈随机的无序排列;纤维素微纤丝聚集体在一个细胞壁各层内的分布密度不同,并且在壁层与壁层相邻的位置密度明显大于壁层内的密度,这一现象在薄壁细胞内表现得更明显;纤维素微纤丝聚集体的尺寸在一个纤维细胞各壁层内差异不大,但在薄壁细胞中差异较大。

【Objective】Cellulose microfibril aggregate is the main component of bamboo cell wall which is important to study. However,bamboo cell wall is too hard to prepare the sample,and the technology with high resolution is not enough. Therefore,it is very different to study the cellulose micrifibril aggregates in bamboo cell wall.【Method】Bamboo strips were delignified by chemical treatment before being immersed in resin. Then the delignified bamboo cell wall was cut and polished by diamond knife which was ready for observing with an atomic force microscopy（ AFM）. The cellulose microfbril aggregates in bamboo fiber and parenchyma cell wall were investigated by Tapping Mode using an AFM.【Result】Height images and phase images were obtained by observing the prepared bamboo samples with an AFM. There were polylamellate structures in both fiber and parenchyma cell wall which changed according to the position in the vascular bundle. The amount of high bright material changed in different position of each layer was calculated by observing the phase images in one vascular bundle. Besides,the high bright material between the neighbor layers was more than other place; the size of high bright materials was similar in fiber cell wall,but different in parenchyma cell wall.【Conclusion】The Tapping Mode in AFM is an effective method to observe bamboo cell wall with pre-treatment which can not only get the image chosen before but also can get the information both on polylamellate structure and on cellulosemicrofibril aggregates in each cell wall layer. Cellulose microfibril aggregates distributed randomly in the cross section of both fiber and parenchyma cell wall. The amount of cellulose microfibril aggregates was various in different layers of bamboo fiber cell wall. Cellulose micrifibril aggregates in fiber cell wall were obviously higher in the edge of each layer than that in the middle place,which was more obvious in the parenchyma cell wall. The size of cellulose microfibril aggregate was almost the same in fiber cell wall,but different in parenchyma cell wall.