薄壁细胞是竹材基本组织中的主要细胞类型起到填充及淀粉贮存作用, 是竹材中重要的力学承载单元之一。 采用共聚焦荧光显微技术对解离后的竹材薄壁细胞形态进行成像观察, 透射电子显微镜成像发现薄壁细胞次生壁呈现宽窄交替的同心层状结构, 且单层厚度在0.2～0.3 μm。 在此基础上利用532 nm共聚焦显微拉曼光谱成像技术原位状态下研究竹材薄壁细胞壁中木质素、 纤维素区域化学, 通过C—H伸缩振动（2 789～3 000 cm-1）特征峰峰高拉曼成像成功的区分出薄壁细胞复合胞间层以及次生壁, 由于空间分辨率限制无法对薄壁细胞次生壁亚层进行区分。 通过对薄壁细胞拉曼光谱380 cm-1（吡喃环C—C—C对称弯曲振动）和1 600 cm-1（木质素苯环伸缩振动）特征峰成像发现其次生壁中纤维素具有明显的区域选择性, 而木质素具有明显的区域选择性, 主要汇聚于复合胞间层及次生壁内层。 与木质素共轭相联的松柏醛/芥子醛, 以酯键和醚键与木质素和半纤维素相联的对羟基肉桂酸类与木质素分布规律类似。 采用偏振光拉曼成像阐明纤维素微纤丝在薄壁细胞与纤维细胞各亚层中的空间取向差异, 拉曼强度比值表明相对于纤维细胞宽层, 纤维细胞窄层及薄壁细胞次生壁中纤维素分子更加趋近垂直于细胞轴向, 也即是大的微纤丝角。 研究结果加深了对毛竹薄壁细胞结构、 细胞壁区域化学及分子取向特性的理解, 能够为高效精准利用竹材提供重要的理论指导。

Ground parenchyma tissue is regarded as the basic structural units, and its functions are storage. In the present work, Confocal fluorescence microscopy was used to visualize the morphology of separated parenchyma. Moreover, TEM image displayed the concentric layering structure of secondary parenchyma wall and the thickness of the sub-layer ranges from 0.2~0.3 μm. Based on the above findings, the top chemistry of lignin and cellulose in parenchyma was studied by 532 nm in situ confocal Raman spectroscopy. The cell wall morphology of parenchyma was observed by integration the band regions from 2 789~3 000 cm-1. Due to the limitation of spatial resolution, the secondary wall cannot be divided into sub-layers. Raman imaging obtained from 380 and 1 600 cm-1 show that the cellulose within the secondary wall of parenchyma was uniform distribution, but the lignin mainly accumulated within the compound middle lamella and its aromaticringconjugated coniferaldehyde and sinapaldehyde displayed the same distribution pattern. Moreover, the distribution pattern of hydrocinnamic acids, which are attached to lignin and hemicelluloses via ester and ether bonds, was also heterogeneous. The ratio of Raman band intensity revealed that the cellulose molecular chain within the parenchyma and narrow layer of fiber wall was more parallel to the cell axis compared to the broad layer of fiber. The above results will deepen our understanding of ultrastructure, cell wall topochemistry and molecular orientation of bamboo parenchyma. It will provide theoretical instruction for the highly efficient and precise utilization of bamboo resources in the further.