基于显微形态学的桉树细胞皱缩及其回复机制与调控研究

Collapse is a serious problem for Eucalyptus wood using as solid wood material. It is an effective method to reduce the degree of cell collapse and improve cell recovery by adjusting drying schedule during kiln drying. Eucalyptus urophylla is used in this project, the cells in the phases which are prone to collapse and recovery during various drying schedules are observed using mirror-observation by scanning electron microscope and image processing technology, the cell collapse and recovery were compared and analyzed quantitatively. Based on the analysis above, the relationships between collapse and recovery and drying schedules and drying parameters were investigated, and then the drying schedules and parameters corresponded to minimum collapse and maximum recovery are determined, the cell types involved in collapse and recovery during drying are founded, the relationships between the amount of recovery and drying schedules and parameters are obtained and finally, the model of cells involved in collapse and recovery during different drying phases corresponded to drying schedules and parameters are created. The model is aid to not only for explaining the mechanism of collapse and recovery and to the research on regulation to collapse and recovery, but also providing theoretical foundation to optimizing drying technology and schedules, preventing collapse and improving high value-added solid wood products.

桉树皱缩是制约其作为实木制品用材的一大干燥缺陷。目前，常规干燥过程中通过调整干燥工艺和参数来减小细胞皱缩程度、提高细胞皱缩回复能力是解决桉树干燥皱缩问题的有效方法。本申请以尾叶桉为研究对象，拟通过创建显微形态学镜像观测法，在干燥过程中针对不同干燥工艺，对木材细胞易发生皱缩及回复的阶段进行细胞显微形态观测，辅以图像处理技术，对细胞的皱缩及回复进行对比和量化统计分析，研究皱缩及回复与干燥工艺及参数之间的关系，确定细胞的最小皱缩及最大回复对应的干燥工艺及参数；确定干燥阶段参与皱缩和回复的细胞类型；确定细胞回复量与干燥工艺及干燥参数的对应关系，最终建立干燥过程中各个阶段参与皱缩的细胞以及发生回复的细胞与干燥参数之间的理论模型。此模型的建立不仅有助于揭示细胞皱缩及回复机理，研究相应的调控措施，而且为合理制定和优化桉树人工林的干燥基准和工艺、消除皱缩、实现其高附加值的实木加工利用提供理论依据。

桉树人工林木材具有作为家具及高附加值实木制品用材的巨大潜力，然而桉木干燥过程中极易出现的皱缩现象严重制约了其实木化利用的进程。为此，本项目选用目前种植面积广泛，具有广阔利用前景的两种桉树人工林木材为研究对象，通过扫描电子显微镜、X射线断层扫描技术等现代分析手段，创建显微形态学镜像观测法，对超声波、冷冻、压缩及预冻-压缩联合预处理后，木材细胞极易发生皱缩及回复的阶段进行显微形态学表征；同时对细胞的皱缩和回复进行对比和量化统计分析；确认了不同干燥阶段参与皱缩和回复的细胞类型，解析了皱缩及回复与干燥工艺及参数之间的关系；阐明了不同预处理条件对桉树材皱缩特性的影响。结果表明，预处理方式不同程度的改变了细胞壁的微观构造，在试材内部形成新的水分迁移通道，释放了干燥应力，破坏了皱缩产生的条件，有效的抑制了木材的干燥皱缩；显微形态学镜像观测法从微观水平能够有效的对细胞皱缩及其回复进行解析，找出皱缩产生的临界参数条件，进而研究皱缩产生与回复的动力因素，解明皱缩调控机制；利用X射线断层扫描技术能够从纵向解析细胞皱缩及其回复的动态过程，并对皱缩程度进行量化统计分析，为从微观角度系统研究皱缩的发展提供了一个新思路。本项目的实施，推动了我国桉树人工林木材高效高质利用的步伐，为解决桉树高附加值利用的瓶颈问题提供理论依据和技术支撑。