北美白蜡木枝桠木年轮生长偏向性的研究

A Study of Growth Ring Eccentricity in North American White Ash Branch Wood

通过实验观察并测定了北美白蜡木(Fraxinus americana L.)的枝条年轮偏向性和应拉木的显微结构及化学特性。通过对白蜡木树枝上侧木及下侧木进行SEM及化学成分分析以期判断应拉木与年轮偏向性的关系。该实验发现白蜡木枝桠木髓心偏向上侧,即下侧的生长比上侧迅速。SEM的观察发现胶质层同时发生于枝桠木上下侧的纤维管胞;化学分析表明枝桠上下侧的纤维含量仅比正常木者稍高2.96-4.45%,而其木质素含量也仅比正常木者低3.33-5.57%。该实验的结论是白蜡木的枝桠木里的应力木在上下两侧都不严重,而白蜡木枝桠木下侧生长迅速造成髓心偏向上侧。

The purpose of the study was to observe growth ring eccentricity, microstructure and analysed chemical characteristics in white ash branches. The wood from upper and lower sides of the branch was studied with SEM and analyzed for chemical composition to find out relationship between occurrence of reaction wood and growth ring eccentricity. Results show that growth ring eccentricity in white ash branches occurred on the upper side because of a faster growth rate at the lower side. SEM observations indicated that gelatinous fiber tracheids occurred both in the upper and lover sides of the branch; and chemical analyses showed the branch wood contained only 2.96%-4.45% higher a-cellulose content and 3.33%-5.57% lower lignin content than that of normal wood. It is conclude that reaction wood in the upper and lower sides of the white ash branches was not observed and the upper growth ring eccentricity was caused by fast growth rate in the lower side of the branch.