Study on the Growth Strain and the Related Structure of Branches and Inclined Seedlings of Eleven Angiosperm Species
Date Issued
2008
Date
2008
Author(s)
Tsai, Ching-Chu
Abstract
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. eleased 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.ccording 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. he 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°.
Subjects
branch
seedlings
epinasty
growth strain
negative gravitropism
MFA
File(s)![Thumbnail Image]()
Loading...
Name
ntu-97-R95b44006-1.pdf
Size
23.32 KB
Format
Adobe PDF
Checksum
(MD5):0eb3120b39bf181a0d25ed479ce54d92