This Article Full Text Full Text (PDF) All Versions of this Article: 134/1/401    most recent pp.103.028357v1 Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via CrossRef Citing Articles via ISI Web of Science (24) Citing Articles via Google Scholar Google Scholar Articles by Cochard, H. Articles by Coutand, C. Search for Related Content PubMed PubMed Citation Articles by Cochard, H. Articles by Coutand, C. Agricola Articles by Cochard, H. Articles by Coutand, C.

WHOLE PLANT AND ECOPHYSIOLOGY

Xylem Wall Collapse in Water-Stressed Pine Needles

Unité Mixte de Recherche Physiologie Intégrée de l'Arbre Fruitier et Forestier, Institut National de la Recherche Agronomique/Université Blaise Pascal, Site de Crouelle, 63039 Clermont-Ferrand, France (H.C., C.C.); Unité Mixte de Recherche Ecologie et Ecophysiologie Forestiére, Institut National de la Recherche Agronomique-Université Henri Poincarré Nancy 1, Boite Postale 239, 54506 Vandoeuvre, France (F.F.); and Institut für Botanik, Universität Innsbruck, Sternwartestrasse 15, A-6020 Innsbruck, Austria (S.M.)

Wall reinforcement in xylem conduits is thought to prevent wall implosion by negative pressures, but direct observations of xylem geometry during water stress are still largely lacking. In this study, we have analyzed the changes in xylem geometry during water stress in needles of four pine species (Pinus spp.). Dehydrated needles were frozen with liquid nitrogen, and xylem cross sections were observed, still frozen, with a cryo-scanning electron microscope and an epifluorescent microscope. Decrease in xylem pressure during drought provoked a progressive collapse of tracheids below a specific threshold pressure (P_collapse) that correlates with the onset of cavitation in the stems. P_collapse was more negative for species with smaller tracheid diameter and thicker walls, suggesting a tradeoff between xylem efficiency, xylem vulnerability to collapse, and the cost of wall stiffening. Upon severe dehydration, tracheid walls were completely collapsed, but lumens still appeared filled with sap. When dehydration proceeded further, tracheids embolized and walls relaxed. Wall collapse in dehydrated needles was rapidly reversed upon rehydration. We discuss the implications of this novel hydraulic trait on the xylem function and on the understanding of pine water relations.

^* Corresponding author; e-mail cochard{at}clermont.inra.fr; fax 33-4-73-62-44-54.

Received June 10, 2003; returned for revision August 31, 2003; accepted September 23, 2003.

This article has been cited by other articles:

				C. J. Willson, P. S. Manos, and R. B. Jackson Hydraulic traits are influenced by phylogenetic history in the drought-resistant, invasive genus Juniperus (Cupressaceae) Am. J. Botany, March 1, 2008; 95(3): 299 - 314. [Abstract] [Full Text] [PDF]

				H. Cochard, J.-S. Venisse, T. S. Barigah, N. Brunel, S. Herbette, A. Guilliot, M. T. Tyree, and S. Sakr Putative Role of Aquaporins in Variable Hydraulic Conductance of Leaves in Response to Light Plant Physiology, January 1, 2007; 143(1): 122 - 133. [Abstract] [Full Text] [PDF]

				A. L. Jacobsen, F. W. Ewers, R. B. Pratt, W. A. Paddock III, and S. D. Davis Do Xylem Fibers Affect Vessel Cavitation Resistance? Plant Physiology, September 1, 2005; 139(1): 546 - 556. [Abstract] [Full Text] [PDF]

				D. Hukin, H. Cochard, E. Dreyer, D. L. Thiec, and M. B. Bogeat-Triboulot Cavitation vulnerability in roots and shoots: does Populus euphratica Oliv., a poplar from arid areas of Central Asia, differ from other poplar species? J. Exp. Bot., August 1, 2005; 56(418): 2003 - 2010. [Abstract] [Full Text] [PDF]

				T. J. Brodribb and N. M. Holbrook Water Stress Deforms Tracheids Peripheral to the Leaf Vein of a Tropical Conifer Plant Physiology, March 1, 2005; 137(3): 1139 - 1146. [Abstract] [Full Text] [PDF]