三倍体毛白杨生长过程中半纤维素分布规律及分子结构研究

Research on the components in wood cell walls is very important to the cultivation of plantation and modification of wood properties. Currently, there are many drawbacks in the investigation of hemicelluloses in wood cell walls, including the inaccuracy of hemicelluloses localization and distribution, structural modification of hemicelluloses during isolation, lack of study in molecular morphology and difficulty in detecting the linkage sites of the attached side chains. In this project, Triploid Populus tomentosa of different ages and anatomical parts will be selected as specimens. The hemicellulose distribution in these preparations will be studied by using cellular immunolabelling in situ, and then the hemicelluloses will be isolated by microwave- and ultrasound-assisted extraction with organic solvents and diluted alkaline solutions. The morphology of molecular chain will be determined by atom force microscopy, and the structure will be detected by gel permeation chromatography, infrared spectroscopy together with nuclear magnetic resonance spectroscopy. The findings of the study will contribute to the methodology on the morphology and structure of hemicelluloses and illustrate the mechanism of high-efficient separation of hemicelluloses. In addition, it will explore the variation of hemicelluloses distribution in the cell walls and elucidate the structural variation of hemicelluloses during the tree growth, providing experimental and theoretical basis for forest directional cultivation.

树木细胞壁组分研究对人工林培育及林木材性改良有重要作用。目前，树木细胞壁中半纤维素组分研究存在分布定位不准确、单一溶剂分离结构不完整、分子链形貌研究缺乏及侧链糖基连接位点检测困难的弊端。本项目拟以不同生长年限、不同部位的三倍体毛白杨为研究对象，采用免疫标记法进行半纤维素的原位检测，以微波、超声波辅助混合有机溶剂体系及稀碱体系实现半纤维素的完整分离，采用原子力显微镜测定半纤维素的分子链形貌及尺寸，结合凝胶渗透色谱、红外光谱、核磁共振技术鉴定三倍体毛白杨半纤维素的分子结构。本项目将完善半纤维素形貌及结构表征的方法，阐明半纤维素高效分离的机理，探索三倍体毛白杨生长过程中半纤维素分布的变化规律，解译三倍体毛白杨生长过程中半纤维素结构的变化，为林木定向培育提供实验依据和理论基础。

树木细胞壁组分研究对人工林培育及林木材性改良具有重要作用。半纤维素作为细胞壁中含量仅次于纤维素的重要基质多糖，直接参与细胞壁的构建。本项目以1~5年生上、中、下部的三倍体毛白杨原料开展研究，以共聚焦拉曼显微技术进行了不同生长年限、不同部位细胞壁多糖分布的原位检测；以碱体系、水热协同碱处理、不同辅助条件及体系实现了半纤维素的完整分离，阐明了不同体系中半纤维素的分离机理；采用凝胶渗透色谱、红外光谱、核磁共振等系列技术全面表征了分离所得半纤维素的结构，完善了半纤维素的结构表征方法。研究发现，三倍体毛白杨细胞壁多糖主要在次生壁和胞间层积累，细胞角隅处基本没有多糖，且1年生细胞壁多糖积累较少，其含量随着树龄的增大而逐渐增多，在第4年达到最高值。树木上部和中部多糖的积累速度快于下部。在生长过程中，三倍体毛白杨半纤维素仅糖基含量发生变化，无明显规律，主要结构为4-O-甲基-D-葡萄糖醛酸-木聚糖。本项目利用微观和化学综合研究，探索了三倍体毛白杨生长过程中半纤维素的分布和结构变化，为林木定向培育提供了实验依据和理论基础。