Skip to Main Content
U.S. Forest Service
Caring for the land and serving people

United States Department of Agriculture

Home > Search > Publication Information

  1. Share via EmailShare on FacebookShare on LinkedInShare on Twitter
    Dislike this pubLike this pub


    Our goals were to quantify how non-embolism inducing pressure gradients influence trunk sapwood specific conductivity (ks) and to compare the impacts of constant and varying pressure gradients on ks with KCl and H20 as the perfusion solutions. We studied six woody species (three conifers and three angiosperms) which varied in pit membrane structure, pit size and frequency of axial water transport across pits (long versus short conduits). Both stepwise ("steady") and nonlinear continuous ("non-steady") decreases in the pressure gradient led to decreased ks in all species but white oak: (Quercus garryana Dougl. ex Hook), a ring-porous and longvesseled angiosperm. In one diffuse-porous angiosperm (red alder, Alnus rubra Bong.) and two conifers (western red cedar, Thuja plicaia Donn. ex D. Don, and Douglas-fir, Pseudotsuga menziesii (Mirb.) Franco), ks was 10-30% higher under steady pressure gradients than under non-steady pressure gradients, and a decrease in the pressure gradient from 0.15 to 0.01 MPa m-1 caused a 20-42% decrease in ks. In another diffuse~porous angiosperm (maple, Acer macrophyllum Pursh) and in a third coniferous species (western hemlock, Tsuga heterophylla (Raf.) Sarg), there was no difference between kg measured under steady and non~steady pressure gradients. With the exception of western red cedar, a conifer with simple pit membranes, the differences in ks between low and high pressure gradients tended to be lower in the conifers than in the diffuse-porous angiosperms. In Douglas-fir, western red cedar and the diffuse-porous angiosperms, ks was higher when measured with KCI than with H20. In white oak, there were no differences in ks whether measured under steady or non-steady pressure gradients, or when xylem was perfused with KCI or H20. The species differences in the behavior of ks suggest that elasticity of the pit membrane was the main factor causing ks to be disproportionate to the pressure gradient and to the different pressure regimes. The results imply that, if nonlinearities in pressure-flux relationships are ignored when modeling tree water relations in vivo, large errors will result in the predictions of tree water status and its impact on stomatal control of transpiration and photosynthesis.

    Publication Notes

    • You may send email to to request a hard copy of this publication.
    • (Please specify exactly which publication you are requesting and your mailing address.)
    • We recommend that you also print this page and attach it to the printout of the article, to retain the full citation information.
    • This article was written and prepared by U.S. Government employees on official time, and is therefore in the public domain.


    Domec, Jean-Christophe; Meinzer, Frederick C.; Lachenbruch, Barbara; Housset, Johann. 2008. Dynamic variation in sapwood specific conductivity in six woody species. Tree Physiology: vol 27 pgs. 1389-1400


    Darcy's law, hydraulic architecture, non-steady, steady, tracheitis, vessels, xylem

    Related Search

    XML: View XML
Show More
Show Fewer
Jump to Top of Page