Cavitation and water fluxes driven by ice water potential in Juglans regia during freeze–thaw cycles

Freeze–thaw cycles induce major hydraulic changes due to liquid-to-ice transition within tree stems. The very low water potential at the ice–liquid interface is crucial as it may cause lysis of living cells as well as water fluxes and embolism in sap conduits, which impacts whole tree–water relation...

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Published inJournal of experimental botany Vol. 67; no. 3; pp. 739 - 750
Main Authors Charra-Vaskou, Katline, Badel, Eric, Charrier, Guillaume, Ponomarenko, Alexandre, Bonhomme, Marc, Foucat, Loïc, Mayr, Stefan, Améglio, Thierry
Format Journal Article
LanguageEnglish
Published England Oxford University Press 01.02.2016
Oxford University Press (OUP)
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Summary:Freeze–thaw cycles induce major hydraulic changes due to liquid-to-ice transition within tree stems. The very low water potential at the ice–liquid interface is crucial as it may cause lysis of living cells as well as water fluxes and embolism in sap conduits, which impacts whole tree–water relations. We investigated water fluxes induced by ice formation during freeze–thaw cycles in Juglans regia L. stems using four non-invasive and complementary approaches: a microdendrometer, magnetic resonance imaging, X-ray microtomography, and ultrasonic acoustic emissions analysis. When the temperature dropped, ice nucleation occurred, probably in the cambium or pith areas, inducing high water potential gradients within the stem. The water was therefore redistributed within the stem toward the ice front. We could thus observe dehydration of the bark’s living cells leading to drastic shrinkage of this tissue, as well as high tension within wood conduits reaching the cavitation threshold in sap vessels. Ultrasonic emissions, which were strictly emitted only during freezing, indicated cavitation events (i.e. bubble formation) following ice formation in the xylem sap. However, embolism formation (i.e. bubble expansion) in stems was observed only on thawing via X-ray microtomography for the first time on the same sample. Ultrasonic emissions were detected during freezing and were not directly related to embolism formation. These results provide new insights into the complex process and dynamics of water movements and ice formation during freeze–thaw cycles in tree stems.
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PMCID: PMC4737071
Editor: Jeremy Pritchard, University of Birmingham
ISSN:0022-0957
1460-2431
DOI:10.1093/jxb/erv486