Skip to Main Content
Bordered pit structure and function determine spatial patterns of air-seeding thresholds in xylem of Douglas-fir (Pseudotsuga menziesii; Pinaceae) trees.Author(s): J.C. Domec; B. Lachenbruch; F.C. Meinzer
Source: American Journal of Botany. 93(11): 1588-1600.
Publication Series: Scientific Journal (JRNL)
PDF: Download Publication (1.03 MB)
DescriptionThe air-seeding hypothesis predicts that xylem embolism resistance is linked directly to bordered pit functioning. We tested this prediction in trunks, roots, and branches at different vertical and radial locations in young and old trees of Pseudotsuga menziesii. Dimensions of bordered pits were measured from light and scanning electron micrographs, and physiological data were from published values. Consistent with observations, calculations showed that earlywood tracheids were more resistant to embolism than latewood tracheids, mainly from earlywood having stretchier pit membranes that can distend and cover the pit aperture. Air seeding that occurs in earlywood appears to happen through gaps between the torus edge and pit border, as shown by the similar calculated pressures required to stretch the membrane over the pit aperture and so cause embolism. Although bordered pit functioning was correlated with tracheid hydraulic diameter, pit pore size and, above all, pit aperture constrained conductivity the most. From roots to branches and from the trunk base to higher on the trunk, hydraulic resistance of the earlywood pit membrane increased significantly because of a decrease in the size of the pit aperture and size and number of margo pores. Moreover, overall wood conductivity decreased, in part owing to lower pit conductivity and a decrease in size and frequency of pits. Structural and functional constraints leading to the tradeoff of efficiency against safety of water transport were also demonstrated at the individual pit level, with a positive correlation between pit membrane resistance on an area basis and the pressure differential required to cause membrane stretching, a characteristic that is essential for pit aspiration.
- You may send email to firstname.lastname@example.org 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.
CitationDomec, J.C.; Lachenbruch, B.; Meinzer, F.C. 2006. Bordered pit structure and function determine spatial patterns of air-seeding thresholds in xylem of Douglas-fir (Pseudotsuga menziesii; Pinaceae) trees. American Journal of Botany. 93(11): 1588-1600.
KeywordsBordered pit, branch, earlywood, embolism, hydraulic architecture, latewood, margo, root, trunk
- Maximum height in a conifer is associated with conflicting requirements for xylem design
- Force-displacement measurements of earlywood bordered pits using a mesomechanical tester
- A broad survey of hydraulic and mechanical safety in the xylem of conifers
XML: View XML