基于共聚焦显微拉曼光谱的毛竹细胞结构和成分研究

采用共聚焦显微拉曼光谱对毛竹薄壁细胞、薄壁纤维过渡细胞和纤维细胞进行研究。通过构建偏最小二乘(PLS)定量区分模型来对这三种细胞中的差异进行分析，结果表明，该区分模型的建模和交互验证决定系数(R2)分别为0.810和0.800，均方根误差(RMSE)分别为0.323和0.332。根据这一模型的回归系数，发现三种细胞的区别主要体现在1 095，1 319和1 636 cm-1三个波数，这三个波数分别为纤维素、半纤维素和木质素的指纹特征峰。以这三个波数为自变量建立多元线性回归(MLR)模型，该回归模型的建模和交互验证决定系数(R2)分别为0.644和0.643，均方根误差(RMSE)分别为0.442和0.443，表明三种细胞在这三个波数处存在明显的差异。对小波变换基线消除后的拉曼光谱信号进行化学成像分析，结果显示，纤维素微纤维与纤维轴成一个很大的角度，这一结构有利于提高细胞的弹性模量和硬度。半纤维素和纤维素微纤维通过氢键相连，并在范德华力的作用下紧密地结合在一起，因此在拉曼化学成像中可以看到半纤维素和纤维素有相似的分布规律。三种细胞的细胞角和胞间层都高度的木质化，从细胞壁外层到内层木质化程度逐渐降低，表明细胞壁的木质化从细胞角和胞间层开始，且木质化程度并不完全。

Revealing the Cell Structure and Formation of Bamboo with Confocal Raman Mic roscopy

Parenchyma cell (PAC) ,transition tissue between parenchyma cell and fiber cell (TC) and fibre cell (FC) of bamboo were studied by confocal Raman microscopy in this paper .Partial least squares regression was applied to establish a quantitative differentiation model for the three types of cells .The result showed that the determination coefficients (R2 ) of calibration and validation were respectively 0.810 and 0.800 ,and the root mean square error (RMSE) were respectively 0.323 and 0.332 . What's more ,three raman bands of 1 095 ,1 319 and 1 636 cm-1 ,verified to the characteristic peaks of pectin ,hemicellulose and lignin ,were found to be the important bands for the differentiation .Subsequently ,these three raman bands were used to es-tablish a multiple linear regression (MLR) model ,and the determination coefficients (R2 ) of calibration and validation of the model were respectively 0.644 and 0.643 ,and the root mean square error (RMSE) were respectively 0.442 and 0.443 .This re-sult showed that there existed obvious difference among the three types of cells in these three raman bands .Finally ,the raman spectral signal processed by wavelet transform to eliminate baseline were used to chemical imaging analysis . These results showed a rather large microfibril angle between cellulose fibrils and fibre axis ,which contributed to higher modulus and hardness of cells .Hemicellulose and cellulose have similar distribution in the raman chemical image ,due to the connection of hemicellulose and cellulose microfiber through hydrogen bond and the closely combination under the action of van der Waals force .The cell corners (CC) and compound middle lamella (CML) were heavily lignified ,and a gradual decrease of lignification from the outer layer to the inner layer of the three cells indicate that lignification was first occurred at the CC and CML ,and the lignification was not fully completed .