Wilson R H, Smith A C, Kacuráková M, Saunders P K, Wellner N, Waldron K W
Institute of Food Research, Norwich Research Park, Norwich NR4 7UA, United Kingdom.
Plant Physiol. 2000 Sep;124(1):397-405. doi: 10.1104/pp.124.1.397.
Polarized one- and two-dimensional infrared spectra were obtained from the epidermis of onion (Allium cepa) under hydrated and mechanically stressed conditions. By Fourier-transform infrared microspectroscopy, the orientation of macromolecules in single cell walls was determined. Cellulose and pectin exhibited little orientation in native epidermal cell walls, but when a mechanical stress was placed on the tissue these molecules showed distinct reorientation as the cells were elongated. When the stress was removed the tissue recovered slightly, but a relatively large plastic deformation remained. The plastic deformation was confirmed in microscopic images by retention of some elongation of cells within the tissue and by residual molecular orientation in the infrared spectra of the cell wall. Two-dimensional infrared spectroscopy was used to determine the nature of the interaction between the polysaccharide networks during deformation. The results provide evidence that cellulose and xyloglucan associate while pectin creates an independent network that exhibits different reorientation rates in the wet onion cell walls. The pectin chains respond faster to oscillation than the more rigid cellulose.
在水合和机械应力条件下，从洋葱（葱属）表皮获得了偏振一维和二维红外光谱。通过傅里叶变换红外显微光谱法，确定了单个细胞壁中大分子的取向。纤维素和果胶在天然表皮细胞壁中几乎没有取向，但当对组织施加机械应力时，随着细胞伸长，这些分子显示出明显的重新取向。当去除应力时，组织略有恢复，但仍保留了相对较大的塑性变形。通过组织内细胞的一些伸长保留以及细胞壁红外光谱中的残余分子取向，在显微图像中证实了塑性变形。二维红外光谱用于确定变形过程中多糖网络之间相互作用的性质。结果提供了证据，表明纤维素和木葡聚糖相互结合，而果胶形成了一个独立的网络，在湿洋葱细胞壁中表现出不同的重新取向速率。果胶链比更刚性的纤维素对振荡的响应更快。
