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Abstract Detail


Stress Tolerance

Hacke, Uwe G. [1], Sperry, John S. [2], Wheeler, James [3], Sikkema, Elzard [2].

How do vestured pits influence water transport?

Vestured pits are characterized by projections from the secondary cell wall that grow into the pit chamber or outer pit aperture. Vestured pits were found to be more common in warm environments that experience drought than in mesic areas and cold climates. However, the reason for this distribution pattern and the function of vestures remains unclear. We studied pit function in nine species that were reported to have vestured pits. The pit area hypothesis states that vulnerability to xylem cavitation depends on the total area of inter-vessel pits per vessel. Based on this hypothesis we tested whether species with vestured pits can afford to have more pit area per vessel for a given cavitation resistance than species without vestures. The underlying assumption was that vestures will stabilize the pit membrane when it aspirates as a result of air-seeding, exposing less membrane area to air and thereby reducing the probability of air-seeding in a given pit membrane sector. The data, however, did not support this idea. Vestured species showed the same relationship between increasing pit area per vessel and vulnerability to cavitation as non-vestured species. Instead, vestured species differed by having higher pit resistances than non-vestured species. This was in part compensated by the fact that vestured species tended to have longer vessels than their non-vestured counterparts at a given cavitation pressure. In one species (Shepherdia canadensis) we also tested whether vestured pits would prevent cavitation fatigue by preventing the pit membrane from stretching and rupturing. However, Shepherdia exhibited fatigue and became more vulnerable to cavitation after an initial cavitation/refilling cycle. Vestures in this species may be too small to stabilize aspirating pit membranes.


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1 - University of Alberta, Renewable Resources, 2-51 Earth Sciences Building, Edmonton, Alberta, T6G 2E3, Canada
2 - University of Utah, Biology, 257 South 1400 East, Salt Lake City, UT, 84112, USA
3 - Harvard University, Organismic and Evolutionary Biology, 16 Divinity Avenue, Cambridge, MA, 02138, USA

Keywords:
vestured pits
cavitation resistance
xylem structure and function.

Presentation Type: Poster:Posters for Topics
Session: P
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM
Number: P77005
Abstract ID:1282


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