常見六種闊葉樹枝條構造的比較

Abstract

本研究對台灣常見的六種闊葉樹側枝枝條進行解剖特徵的觀察和比較，這六樹種分別是黑板樹、豔紫荊、樟樹、榕樹、台灣欒樹和小葉欖仁。解剖特徵的觀察項目，分別為髓心位置、偏心率趨勢、膠質纖維分布區域、纖維細胞面積、纖維細胞壁厚度和纖維細胞腔佔整個細胞比例等六項。樣本枝條選取水平展開與垂軸的夾角，盡量侷限在七十度到一百一十度之間，而且枝條橫切面的直徑大多小於五公分。 由側枝枝條橫切面髓心位置的分布觀察比較，發現台灣欒樹和小葉欖仁樣本的髓心位置是偏向枝條橫切面的上側，而黑板樹、豔紫荊、樟樹和榕樹的髓心位置並沒有固定的偏向。觀察此六種闊葉樹的側枝枝條距離主幹五公分到二十五公分處的枝條偏心率趨勢，發現黑板樹樣本呈現出枝條偏心率遞減的趨勢，而豔紫荊、樟樹、榕樹、台灣欒樹和小葉欖仁等五種樣本無法清楚歸納出枝條偏心率的趨勢。由膠質纖維分布區域的觀察結果得知，黑板樹樣本未發現膠質纖維的存在，豔紫荊和樟樹樣本的膠質纖維可在橫切面的上下二側發現，而榕樹、台灣欒樹和小葉欖仁樣本的膠質纖維主要出現在橫切面的上側。此外，在側枝枝條纖維細胞的觀察上，發現除了台灣欒樹樣本橫切面下側的纖維細胞面積比上側者大外，黑板樹、豔紫荊、樟樹、榕樹和小葉欖仁的樣本在枝條橫切面的上側、下側和旁側三者間的纖維細胞面積大小並無顯著差異。在纖維細胞壁厚度試驗方面，黑板樹和小葉欖仁樣本橫切面的上側纖維細胞壁較厚，豔紫荊和樟樹的纖維細胞壁則是上、下、旁三者間無顯著差異，而榕樹和台灣欒樹在不同側枝枝條的纖維細胞壁之厚度並不一致，無法清楚歸納。最後，發現黑板樹、台灣欒樹和小葉欖仁三者的側枝枝條纖維細胞腔佔整個細胞的比例，在橫切面上側比例較小，樟樹樣本則是枝條上、下、旁側都無顯著差異，而豔紫荊和榕樹呈現不一致的結果。 本研究結果顯示，闊葉樹種彼此間的多樣化差異。將來在抗張材的研究上，除了解剖特徵之觀察外，還需要利用其他方法的輔助，如生長應力測試或化學組成分析，幫助我們進一步對闊葉樹抗張材的瞭解。

The purpose of this thesis is to analysis the horizontal branches of 6 broad-leaved trees on campus, which are Alstonia scholaris, Bauhinia blakeana, Cinnamomum camphora, Ficus microcarpa, Koelreuteria henryi and Terminalia mantaly. The selected horizontal branches are at the angle between 70° and 110° to vertical and the diameter of branch is less than 5 cm. The position of pith, eccentricity, distribution of gelatinous fiber, fiber domain, fiber thickness of cell wall and ratio of lumen to whole cell were investigated. The pith positions of the branches between 5 and 25 cm from K. henryi and T. mantaly are near the upside, but those from A. scholaris, B. blakeana, C. camphora and F. microcarpa do not have constant position. The eccentricity of the branches of A. scholaris, whose spans to main stem between 5 and 25 cm, declined gradually, but those eccentricity from B. blakeana, C. camphora, F. microcarpa, K. henryi and T. mantaly are not constant. Gelatinous fibers in branches of A. scholaris were not found. The gelatinous fibers from B. blakeana and C. camphora are located both upside and downside, and those from F. microcarpa, K. henryi and T. mantaly are at the upside. The fiber areas that are from the downside of K. henryi are bigger than that of upside, but the fiber area from A. scholaris, B. blakeana, C. camphora, F. microcarpa and T. mantaly do not have difference between upside and downside. The thickness of cell wall from the upside of A. scholaris and T. mantaly is thicker than downside. The thickness of cell wall from B. blakeana and C. camphora is alike between upside and downside side. The F. microcarpa and K. henryi have different results on branches. The ratios of the lumen to the whole cell from the upside branch of A. scholaris, K. henryi and T. mantaly are bigger than those of downside. Those of C. camphora are equal between upside and downside. However, the branches of B. blakeana and F. microcarpa are difficult to conclude. The results of anatomic analyses concluded that the branches of 6 broad-leaved trees are polymorphic. Besides our results, other experiments such as growth strain test and chemical elements analysis are needed to understand the formation of tension wood in the broad-leaved trees.