- 學位論文
十一種被子植物枝條及傾斜苗木主幹生長應變與相關構造之研究
Study on the Growth Strain and the Related Structure of Branches and Inclined Seedlings of Eleven Angiosperm Species
摘要
本篇論文旨在探討生長應力於木本被子植物中的生物功能，及其與木材解剖構造之關係。首先，傾斜主幹生長應力的分布在目前的研究中受到最多的關注，並且直覺性地將結果應用於樹木枝條，然而相關實驗證明仍然缺乏。其次，試圖應用前人在傾斜主幹相關研究中所建立的假說，以枝條研究文獻為佐證，解釋本實驗中樹木枝條為了產生生長應力所生成的相關構造。最後試圖觀察樹木向上彎曲所需之生物性應力的形成過程。 本實驗以測量釋放生長應變的方式研究生長應力的分布，將11具樹木枝條中21個有效測量點區分為4種型式。第I至III型測量點產生向上彎曲力矩（負向重性生長），而第IV型測量點產生向下彎曲力矩（偏上生長）。結果推測第I型測量點最普遍存在於被子植物枝條中，不同於傾斜主幹中最常見的為第II型以及第III型。第IV型測量點只存在於已落葉的台灣欒樹枝條（Koelreuteria henryi）中，其具有相反於第I型測量點的生長應變分布，類似重力解除後的回彈效應。 由枝條產生反應構造的解剖研究，結合前人的理論推測，枝條能夠藉由徑生長來抵抗彎曲應力，例如烏心石（Michelia compressa）。或者枝條能夠調控上、下側差異性生長，以減低應力對木材造成的形變，例如榕樹（Ficus microcarpa）、白雞油（Fraxinus griffithii）、福木（Garcinia multiflora）。又或者改變微纖維排列角度，以控制纖維細胞延展方向，例如福木及台灣欒樹。微纖維角度的測量結果支持除了落葉產生的物理效應外，另有生物性應力產生，共同影響第IV型測量點的應變分布。有些樹種亦藉由生成抗張力強的膠質纖維，例如榕樹、小葉欖仁（Terminalia mantaly），青剛櫟（Cyclobalanopsis glauca），台灣櫸（Zelkova serrata）。雖然膠質纖維被視為是典型引張材的特徵，然而膠質纖維的出現與不同形式的應力分布沒有顯著關聯。 最後以連續監測傾倒苗木應變的方式，將彎曲應力扣除，觀察生物性應力的形成。九種苗木傾斜30°，其達到平衡位置所需的時間皆介於10~20天之內。同時將台灣櫸以及福木苗木各三棵傾斜30°，結果顯示回復平衡速度與物種無關，然而平衡值在不同物種間有顯著不同。將台灣欒樹傾倒於30°以及60°，結果顯示傾斜角60°時苗木的反應較快速。
並列摘要
The present thesis is aimed at further understanding the biological function of growth stress and related structures in woody angiosperms. First, the growth stress distribution in the tilted trunks has been intensively studied and intuitively applied on the branches; however, the supported data are still lacking. Second, the bases of the structural supports used by these branches to resist the bending stress were accessed. Furthermore, the generation of the biological stress to balance the bending moment of tilted trunk of 9 species was traced. Released growth strains (RGSs) related to growth stress were measured to distinguish 21 measuring site of 11 branches from 8 species into four types. The first three types of measuring site produced upward bending moment (negative gravitropism), and the fourth type of branches produced downward bending moment (epinasty). Based on our results, type I measuring site was suggested to be the most widespread in branches while type II and III were prevailing in the tilted trunks. Type IV was found only in Koelreuteria henryi during leaf-falling season and was the reverse of type I, partly resembling the spring back effect. According to the study of wood anatomy, branches can resist the bending stress (i) by increasing radial growth, such as Michelia compressa; (ii) by inducing differential cambial activity, such as Ficus microcarpa, Fraxinus griffithii, Garcinia multiflora and K. henryi; and/or (iii) by regulating angles of microfibrils (MFAs), such as G. multiflora and K. henryi, which controlled the expansion direction and thus resulting growth stress. The stress distribution of Type IV resembles the spring back effect caused by defoliation; however, the results from MFAs showed that biological stress may also be involved. F. microcarpa, Terminalia mantaly, Cyclobalanopsis glauca, Zelkova serrata produced gelatinous fibers (G-fibers) which bearing high tensile stress in their tension wood. Although it is an important character of typical tension wood, the presence of G-fiber seemed not related to the RGSs typing. The formation of the biological strain was investigated separately from bending stress by successively recording the strains after inclining the seedlings. The time for attaining equilibrium in the tilted seedlings (from 9 species) at 30° was 10~20 day. Each three seedlings of Z. serrata and G. multiflora were inclined at 30° to examine the variation within species. The results indicated that the equilibrium time was species-independent, while the values of equilibrium strains were species-dependent. The seedlings of K. henryi were inclined at 30° and 60° and the result showed that the seedlings inclined at 60° turned up earlier than those at 30°.
參考文獻
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