黄藤细胞壁木质素区域化学分子光谱成像研究

整合共聚焦显微荧光和拉曼光谱成像技术系统研究了黄藤藤茎组织中不同类型细胞以及同一细胞不同形态区域的木质素区域化学特点。共聚焦荧光成像表明黄藤藤茎组织中木质素主要汇聚于初生木质部导管、次生木质部导管、维管束间的薄壁组织细胞以及纤维细胞角隅区。基于荧光光谱差异的光谱成像线性拆分结果显示纤维细胞次生壁由宽、窄层交替的同心层状结构组成,且窄层具有更高的木质化程度。比较黄藤、毛竹、芒草、毛白杨和虎皮松拉曼光谱发现黄藤材细胞壁拉曼光谱与阔叶木毛白杨类似,证实了黄藤材的化学组成更加趋近于阔叶木毛白杨。对拉曼光谱中木质素特征峰成像进一步揭示出纤维细胞中木质素不均一的分布规律:其中细胞角隅胞间层和复合胞间层的拉曼信号强度最高,表明较高的木质化程度,其次是次生壁中的窄层,而次生壁宽层中拉曼特征峰强度最低,这一分布规律与竹材纤维细胞中木质素分布规律类似。宽、窄层中木质素不仅存在浓度上的差异,而且木质素基本结构单元的比例亦不同。采取光谱去卷积的方法排除了碳水化合物的影响,发现窄层中愈创木基(G型)木质素与紫丁香基木质素(S型)比例为0.19,而在宽层中这一比值为0.14,这一结果亦解释了宽、窄层荧光光谱间的差异。该研究结果对探索黄藤细胞壁生物合成及力学响应机制研究具有重要理论指导意义。

The Lignin Topochemistry of Daemonorops margaritae (Hance)Becc.by Molecular Spectroscopic Imaging

The topochemistry of lignin in commercial rattan (Daemonorops margaritae (Hance))cell wall was investigated by combining fluorescence confocal laser scanning microscopy and confocal Raman microscopy at cellular and sub-cellular level.Con-focal fluorescence images indicated that within the stem tissues of rattan higher fluorescence intensity and thus higher lignin con-centration was visualized in proto-,meta-xylem vessel,parenchyma between vascular bundles and the cell corner middle lamella regions of fiber.More importantly,linear unmixing images based on the difference of fluorescence spectra revealed that the Rat-tan fiber secondary wall was divided into alternations alternating broad and narrow layers and the lignin concentration was higher in the narrow layers.Comparing the average Raman spectra extracted from the D .margaritae (Hance),P .heterocycla cv pu-bescens ,M.sinensis ,P .tomentosa and P .bungeana Zucc.secondary wall indicated that rattan fiber wall had a comparable mo-lecular structure as hardwood poplar.Raman images by calculating the lignin band at 1598 cm-1 further confirmed the heteroge-neous distribution of lignin at cellular level.It was found that the cell corner middle lamella of fiber had the highest lignin concen-tration followed by the narrow layer,and had the fewest in the broad layer,which was in accordance with the topochemical fea-tures of bamboo fiber.Meanwhile,Raman spectra analysis confirmed that other than the variation in lignin concentration be-tween the broad and narrow layers,they also displayed differences in ratio of lignin structure units.Specifically,the ratio of G lignin to S lignin was 0.19 and 0.14 in the narrow and broad layers,respectively.The present results will provide a theoretical instruction for rattan cell wall biosynthesis and the origin of cell wall reaction stress.