A Century Of Wood Anatomy and 75 Years Of IAWA
Jansen, Steven .
The structure and function of bordered pits in vascular plants.
THE study of bordered pits and their biological significance in xylem has fascinated plant anatomists for centuries. The structure refers to openings in the secondary cell wall of tracheary elements in which the pit membrane is typically overarched by the secondary cell wall. Recent advances in the field of xylem physiology have stimulated a renewed interest in the micromorphology of bordered pits in water conducting elements of vascular plants, especially with respects to evolutionary trends and efficiency vs. safety trade-offs underlying pit structure and function. It is now apparent that pit membrane structure exerts a strong influence over the regulation and efficiency of water transport through the vascular system and the resistance of this system to dysfunction via air entry (cavitation) and xylem bourn pathogens. Nevertheless, our knowledge of pit and pit membrane (ultra)structure is still based on a relatively small number of species. Pit structure exhibits greater variation than previously thought, as can be illustrated by the homoplastic nature of vestured pits, the distribution of torus-margo pit membranes and plasmodesmata associated thickenings on pit membranes in narrow tracheary elements of angiosperms. Anatomical data are reviewed in the context of water transport processes in tracheary elements. The ability of woody plants to vary the structure of bordered pits in response to environmental conditions is also discussed. Moreover, differences in bordered pit structure have a profound effect on the properties of wood, which has interesting applications with respect to chemical impregnability of gasses and liquids in commercial timbers. The mechanism by which the structure of bordered pits is controlled is still uncertain, but the application of molecular techniques is likely to enable modification of this process.
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International Association of Wood Anatomists
1 - Royal Botanic Gardens, Kew, Jodrell Laboratory, Molecular Systematics Section, Richmond, Surrey, TW9 3DS, United Kingdom
Presentation Type: Symposium or Colloquium Presentation
Date: Tuesday, August 1st, 2006
Time: 3:45 PM