文献综述：
应力木研究进展
摘 要：树干生长时，由于环境因素影响而产生倾斜，为了“修正”生长方向，树木会形成应力木（reaction wood）。应力木与正常的木材在构造特征、物理及化学性质上均有不同，是树木中的非正常材。应力木的形成是树木一种生理作用，是使倾斜树干恢复到垂直的方位，或维持树枝的自然角度方向。对于被子植物树种，受应力影响通常会在树干上侧形成应拉木（tension wood），而裸子植物树种则在树干下侧形成应压木（compression wood）。应拉木区域的纤维会出现胶质层（gelatinous layer, G-layer），但前人研究发现并不是所有的应拉木均产生胶质层。而应压木区域的管胞常出现螺纹裂隙，且应压木区域木质素含量较高。通过对近年来应力木形成及特性的研究，本文综述了应力木形成机理，阐述了应力木与对应木在木材构造和理化性能的差异，分析了不同树种应力木与植物进化的关系，最终提出了应力木研究及应力木加工利用的发展趋势。
关键词：应力木；形成机理；裸子植物；被子植物；应压木；应拉木
Research status of reaction wood
Abstract: By different environment effects during trees growing, the stems could be inclined by various reasons. For modifying the geometry of trees, the reaction wood is formed on the upper side of the stems for angiosperm trees, and the lower side of the stems for gymnosperm trees. The reaction wood for angiosperms is known as tension wood, while for gymnosperms is compression wood. The gelatinous layer (G-layer) would appear in fibers of tension wood from angiosperms, although not for all. For the tracheid of compression wood, the helical cavities on cell wall may play an important role in relaxing compressive strains at the cellular level, and more lignin content could be detected in compression wood. is different from normal wood in physical and chemical properties. It is the abnormal wood in trees. Based on the researches related with the formation and characteristics of reaction wood, the formation mechanism of reaction wood is summarized. The differences on the anatomical characteristics and physical-chemical properties of reaction wood comparing with normal wood are expounded. The relationship between the formation of reaction wood and plant evolution is discussed. And finally the suggestions on future research of reaction wood, also the processing and utilization of reaction wood, are proposed.
Keywords: reaction wood; formation mechanism; gymnosperms; angiosperms; compression wood; tension wood
1前言
应力木是树木中非正常的木材组织，树木在生长过程中如果受到环境因素的影响，如强风、土壤滑坡等，树干会产生倾斜；而为了保证树木直立生长，倾斜的树木会产生一些生理生态反应对自身的生长状态进行一定的调整，在此条件下形成的木质部（即应力木）与正常状态下形成的木质部在解剖特性上有着明显的不同。通常，针叶树髓心偏向于倾斜树干或树枝的上侧，在下侧年轮较宽处形成应压木；阔叶树髓心偏向于倾斜树干或树枝的下侧，在上侧年轮较宽处形成应拉木。但研究发现，在一些阔叶树中髓心偏向上侧，其中有些树种在上侧年轮较窄处形成了应拉木，而有些树种却未形成应拉木，反而在下侧年轮较宽处形成了类似应压木的应力木，这种特殊现象在黄杨木中已经得到深入研究。
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