AOBPreview published online on May 21, 2003
Annals of Botany, doi:10.1093/aob/mcg117
© 2003 by Annals of Botany Company
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Submitted on October 4, 2002
Affiliation of the authors:
1 Department of Forest Ecosystem Science, University of Maine, Orono, ME 04469, USA; Wood Science and Technology, University of Maine, Orono, ME 04469, USA;
2 Department of Forest Ecosystem Science, University of Maine, Orono, ME 04469, USA;
3 Wood Science and Technology, University of Maine, Orono, ME 04469, USA
* To whom correspondence should be addressed. E-mail: RichardJagels{at}umenfa.maine.edu.
The xylem of Metasequoia glyptostroboides Hu et Cheng is characterized by very low density (average specific gravity = 0·27) and tracheids with relatively large dimensions (length and diameter). The microfibril angle in the S2 layer of tracheid walls is large, even in outer rings, suggesting a cambial response to compressive rather than tensile stresses. In some cases, this compressive stress is converted to irreversible strain (plastic deformation), as evidenced by cell wall corrugations. The heartwood is moderately decay resistant, helping to prevent Brazier buckling. These xylem properties are referenced to the measured bending properties of modulus of rupture and modulus of elasticity, and compared with other low-to-moderate density conifers. The design strategy for Metasequoia is to produce a mechanically weak but hydraulically efficient xylem that permits rapid height growth and crown development to capture and dominate a wet site environment. The adaptability of these features to a high-latitude Eocene palaeoenvironment is discussed.
Revised on February 10, 2003
Accepted on April 11, 2003
Palaeo-adaptive Properties of the Xylem of Metasequoia: Mechanical/Hydraulic Compromises
RICHARD JAGELS1*,
Key words: Metasequoia, xylem conduction, xylem strength, decay resistance, microfibril angle, plastic deformation, Eocene, palaeoecology.
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