A Century Of Wood Anatomy and 75 Years Of IAWA
Hacke, Uwe G. , Sperry, John S. , Feild, Taylor , Elzard, Sikkema , Sano, Yuzou .
Wood structure and function in basal angiosperms.
PREVIOUS work indicates 1) that homogenous inter-vessel pit membranes of eudicots have approximately 60 times the hydraulic resistance of torus-margo pit membranes in conifers, and 2) that vulnerability to cavitation in eudicot vessels increases with greater total area of inter-vessel pitting. These results suggest that the vesseless wood of basal angiosperms might have a much lower hydraulic conductivity than conifer wood because it combines short tracheids with homogenous pit membranes. Vesseless angiosperms might also be extremely resistant to cavitation because of their necessarily small area of inter-tracheid pitting. We are testing these hypotheses in an ongoing survey of over a dozen vesseless angiosperms from the Winteraceae, Trochodendraceae, Amborellaceae, and Tetracentraceae. For comparison we are sampling related species with primitive vessels from the Chloranthaceae, Austrobaileyaceae, Himantandraceae, Trimeniaceae, Illiciaceae, and other basal families. Contrary to hypotheses, preliminary results indicate that vesseless angiosperm wood has only slightly lower conductivities than conifer wood of the same average tracheid diameter. The flow resistance through inter-tracheid pits of basal angiosperms is only slightly greater on average than through the torus-margo pits of conifers-and much less so than through inter-vessel eudicot pits. Angiosperm tracheids are also more vulnerable to cavitation than expected for their pit area. They are, however, considerably more resistant to cavitation as a group (mean cavitation pressures from -2 to -6 MPa) than their closest vessel-bearing relatives (mean cavitation pressures from -0.5 to -3.4 MPa). Collectively, these preliminary results suggest that the inter-tracheid pit membranes are significantly more porous than inter-vessel pit membranes. This is being investigated with SEM observations and air-permeability tests of the inter-tracheid pit membranes. Pit structure and function in these vesseless groups is apparently quite different from that in eudicot vessels and may reflect degradation of the pit membrane at an initial phase of vessel evolution.
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1 - University of Utah, Department of Biology, 257 S. 1400 E., Salt Lake City, Utah, 84112, USA
2 - Tulane University, Department of Ecology and Evolutionary Biology, Dinwiddie 310, New Orleans, Louisiana, 70118-5698, USA
3 - Hokkaido University, Facualty of Agriculture, Lab Of Wood Bio, Kita-9, Nishi-9, Sapporo, 060-8589, Japan
xylem structure and function
Presentation Type: Symposium or Colloquium Presentation
Date: Tuesday, August 1st, 2006
Time: 4:15 PM