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Abstract Detail


Biomechanics

Koehler, Lothar [1], Ewers, Frank, W [2], Mansfield, Shawn [3], Telewski, Frank, W [1].

Impact and Function of Lignin Monomer Composition in Poplar Wood.

Wood, or secondary xylem, is composed of three main components - cellulose, hemicelluloses and lignin. Tailored arrangement of these building blocks from molecular architecture to cell-wall structure and tissue morphology makes wood a very elaborate natural composite that effectively meets manifold requirements such as mechanical stability and energy dissipation, water conduction, and conduction and storage of nutrients.
While the impact of overall lignin content on wood properties and change in lignin content as a response of the plant to various stresses received considerable attention in the past, impact and function of lignin monomer composition remains indistinct.
In the present study we analyze the consequences of genetically increased lignin syringyl content for wood composition, structure, and mechanical and hydraulic properties and the ability of the tree to respond to wind influence during growth.
Wood from 4 month old poplar trees (P. tremula x P. alba, clone 717) with gradual increases in the syringyl to guaiacyl ratio of the lignin due to genetically introduced over-expression of ferulate 5-hydroxylase (F5H) is used in this study. Wind exposure is simulated by daily manual flexing during growth. Differences between clones in response to this thigmomorphogenetic stimulus are investigated in terms of vulnerability to embolism, cellulose microfibrillar angle and mechanical properties. Lignin analysis of trees exposed to simulated wind reveals that lignin composition also is modified naturally by the tree in response to mechanical stress as a means of adjusting mechanical properties according to environmental requirements.
Stiffness in tension and compression was measured to investigate the immediate impact of lignin composition and is discussed in relation to the ecologically more relevant property of flexural stiffness and viscoelastic damping of mechanical energy.


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1 - Michigan State University, Plant Biology, 166 Plant Biology Building, East Lansing, MI, 48824, USA
2 - California State Polytechnic University, Biological Sciences, 3801 West Temple Avenue, Pomona, CA, 91768, USA
3 - University of British Columbia, Department of Wood Science, Vancouver, BC, Canada

Keywords:
biomechanics
cavitation resistance
modulus of elasticity
viscoelastic damping.

Presentation Type: Oral Paper:Papers for Topics
Session: CP13
Location: Boulevard C/Hilton
Date: Monday, July 9th, 2007
Time: 11:15 AM
Number: CP13001
Abstract ID:2277


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