拉曼光谱对高地钩叶藤纤维S2层主要成分的预测

棕榈藤(rattan)属于棕榈科(Palmae)省藤亚科藤类植物,是一种产于热带森林中,仅次于木材和竹材的、重要的非木材林产品,具有很高的经济价值和开发前景。全球棕榈藤总共有13个属660余种,其中我国自然分布有4属37种5变种,但有较高经济价值的不到30种。由于目前对棕榈藤的细胞结构,尤其是藤纤维的细胞壁结构知之甚少,严重限制了对棕榈藤材的研究和加工利用。因此,为构建棕榈藤材纤维细胞壁结构模型,以高地钩叶藤(Plectocomia himalayana Griff.)为研究对象,对其基部、 2 m处、中部和梢部四个部位分别截取试样、软化、聚乙二醇包埋、切片。切片在室温下经0.2 mol·L-1的硼氢化钠(NaBH4)溶液浸泡5~6 h后用蒸馏水洗净,利用LabRam XploRA显微共聚焦拉曼光谱仪,采用逐点扫描显微探针成像方法获取光谱数据集。将获得的光谱数据利用LabSpec5软件进行处理,从而得到藤茎不同部位藤皮、藤中、藤芯处纤维细胞次生壁中层(S2)主要成分,即纤维素、半纤维素、木质素相对含量,并就相对含量在径向、轴向变异进行了分析。结果表明,在径向上,高地钩叶藤藤皮处纤维细胞S2层纤维素与半纤维素相对含量最高,木质素相对含量最低;而藤芯处纤维细胞S2层纤维素与半纤维素相对含量最低,木质素相对含量最高;藤中处纤维素、半纤维素及木质素相对含量居中。在轴向上即不同藤龄处,藤皮纤维细胞S2层纤维素和半纤维素的相对含量在2 m处最大,木质素的相对含量在梢部最大;藤芯纤维细胞S2层纤维素、木质素、半纤维素的相对含量分别在中部、 2 m处、基部处最大。藤皮、藤芯与藤茎一样,纤维细胞S2层纤维素相对含量最小值在梢部,半纤维素和木质素相对含量均在中部最少。分析可知,棕榈藤藤茎不同部位,藤纤维细胞壁中层(S2)纤维素、半纤维素及木质素相对含量是不同的。

Prediction of the Main Components in S2 of Plectocomia himalayana Fiber Based on Raman Spectra

Rattan, belonging to Calamoideae of Palmae, is a multipurpose plant resource found in highly tropical forest, and it is an important non-timber forest product inferior to timber and bamboo, with high economic value and development prospects. There are 13 genera and more than 660 species in the world, of which 4 genera and 37 species of 5 varieties are naturally distributed in China, but there are less than 30 species with high economic value. At present, little is known about the cell structure of rattan, especially the cell wall structure of fiber, which seriously limits the research, processing and utilization of rattan. Therefore, in order to construct the fiber wall structure model of rattan, Plectocomia himalayana was chosen as the research material, and from which samples were cut, softened, embedded with polyethylene glycol and sliced at the base, 2 m, middle and tip respectively. After the slices were soaked in 0.2 mol·L-1 NaBH4 for 5~6 h at room temperature and washed with distilled water, the spectral data were obtained by point-by-point scanning microscopic probe imaging method with the LabRam XploRA microscopic confocal Raman spectrometer. The relative content of cellulose, hemicellulose and lignin in the central layer of secondary wall(S2) of fiber in cortex, middle layer and core at different parts of P. himalayana cane was obtained after the spectral data were processed by LabSpec 5 software, and then the variation of relative content in radial direction and axial direction was also analyzed. The research results show that, in terms of S2 of fiber at 2 m, the relative content of cellulose and hemicellulose is the highest and the relative content of lignin is the lowest in cortex, while the relative content of cellulose and hemicellulose is the lowest and the relative content of lignin is the highest in core, and the relative content of cellulose, hemicellulose and lignin in middle layer is between that of cortex and core in the radial direction. In the axial direction, the relative content of cellulose and hemicellulose of S2 of fiber in cortex is the highest at 2 m, and that of lignin in tip is the highest. The relative content of cellulose, lignin and hemicellulose of S2 of fiber in core is the highest at the middle, 2 m and base respectively. The cortex and core are the same as cane of rattan, the relative content of cellulose in S2 of fiber is the minimum in the tip, and that of hemicellulose and lignin is the least in the middle. Based on the above analysis, the relative contents of cellulose, hemicellulose and lignin in S2 of rattan fiber are different in different parts of rattan.