Developmental and Structural Section
Hung, Li-Fen , Kuo-Huang, Ling-Long .
The growth strain and anatomical characteristics of tension wood in artificially inclined seedlings of Koelreuteria henryi Dummer.
Tension wood (TW) plays an important role in maintaining the optimal tree architecture of angiosperm trees to maximize light interception. Both biological and physical aspects of TW are essential in understanding the mechanism of stem or branch re-orientation. The graceful tree-form of Koelreuteria henryi Dummer and its versatile branches make it an appropriate material for related research. In this study,we inclined 2-year-old seedlings and investigated the angle change, surface growth strain (SGS) distribution, TW formation and related anatomical characteristics during the up-righting process. The pinning method was performed to examine the wood formation of the inclined and the upright seedlings. Six seedlings were artificially inclined at about 30Â° to the vertical and six were kept upright as control. Pictures were taken weekly to trace the angle change of the seedlings. The SGS and related structures of 3 inclined and 3 upright seedlings were examined at the time of 3 month and 6 month after inclination. The inclined seedlings gradually restored their upright position in the first 3 month and then slowed down. Compared to the upright seedlings, all inclined seedlings exhibited strong negative, contractile strains on the upper side of the stems.The negative value of growth strain parameter (a) indicates the intrinsic upward moving force of the tilted stems that pulls the stem back to the upright position. Eccentric growth and crescent TW zone containing gelatinous fibers (G-fibers) were only observed in the upper side of inclined stems in the cross section. By the pinning method, we verified that at the beginning of inclination G-fibers originated from the enlarging xylary cells and then the newly divided fiber cells. The TW formation was found to last for only about 3 month. The ultrastructural study revealed that the secondary wall of the normal wood fiber (NW) consists of S1+S2+S3, while that of the TW fiber consists of S1 and an additional gelatinous layer (G-layer). The microfibrils in the G-layer are almost parallel to the axis of the G fiber. The histochemical tests confirmed that the G-layer consists of mainly cellulose and lignin was not detected in the G-layer.
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1 - National Taiwan University, Institute of Ecology and Evolutionary Biology, Room 1152, Life Science Building, No. 1, Sec. 4 Roosevelt Road, Taipei, 10617, Taiwan
2 - National Taiwan University, Department of Life Science, Room 1152, Life Science Building, , No. 1, Sec. 4 Roosevelt Road, Taipei, 10617, Taiwan
Koelreuteria henryi Dummer.
Presentation Type: Poster:Posters for Sections
Location: Grand Salon A - D/Riverside Hilton
Date: Monday, July 29th, 2013
Time: 5:30 PM
Candidate for Awards:Developmental and Structural Section best poster