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JXB Advance Access published online on October 19, 2009
Journal of Experimental Botany, doi:10.1093/jxb/erp298
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© The Author [2009]. Published by Oxford University Press [on behalf of the Society for Experimental Biology]. All rights reserved. For Permissions, please e-mail: journals.permissions@oxfordjournals.org

RESEARCH PAPER

The effects of sap ionic composition on xylem vulnerability to cavitation

Hervé Cochard1,2,*, Stéphane Herbette1,2, Encarni Hernández3, Teemu Hölttä4,5 and Maurizio Mencuccini4

1INRA, UMR 547 PIAF, F-63100 Clermont-Ferrand, France
2Université Blaise Pascal, UMR 547 PIAF, F-63177, Aubière, France
3CEAM Dept. Ecologia, Fase VU Alicante, Box 99, E-03080 Alicante, Spain
4School of GeoSciences, University of Edinburgh, Edinburgh EH9 3JN, UK
5Department of Forest Ecology, PO Box 24, University of Helsinki, FIN-00014, Finland

* To whom correspondence should be addressed: E-mail: cochard{at}clermont.inra.fr

Recent evidence of ion-mediated changes in pit membrane porosity suggests that plants may modulate the hydraulic conductance of their xylem conduits. Under the current paradigm, membrane porosity also determines conduit vulnerability to water stress-induced cavitation. Therefore, the hypothesis of an ion-mediated regulation of xylem vulnerability to cavitation in trees was tested. Segments of five Angiosperm and two Gymnosperm species were infiltrated with ultra-pure deionized water as a reference fluid or with a 50 mM KCl solution. KCl had a strong impact on segment conductance with either a positive or a negative effect across species. When 1 mM CaCl2 was added to the reference solution, the effect of KCl was minimized for most species. By contrast, segment vulnerability to cavitation was only slightly influenced by the presence of KCl in the solution. From this it was concluded that the mechanisms controlling pit membrane permeability to water flow and its resistance to the penetration of air bubbles are largely uncoupled, which suggests that the hypothesis of a porous structure of pit membranes should be revisited.

Key words: Cavitation, hydraulic conductance, pectin, pit membrane, xylem

Received 30 June 2009; Revised 9 September 2009 Accepted 14 September 2009


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