title: Ultrasonic emissions during ice nucleation and propagation in plant xylem.
abstract: Ultrasonic acoustic emission analysis enables nondestructive monitoring of damage in dehydrating or freezing plant xylem. We studied acoustic emissions (AE) in freezing stems during ice nucleation and propagation, by combining acoustic and infrared thermography techniques and controlling the ice nucleation point. Ultrasonic activity in freezing samples of Picea abies showed two distinct phases: the first on ice nucleation and propagation (up to 50 AE s(-1) ; reversely proportional to the distance to ice nucleation point), and the second (up to 2.5 AE s(-1) ) after dissipation of the exothermal heat. Identical patterns were observed in other conifer and angiosperm species. The complex AE patterns are explained by the low water potential of ice at the ice-liquid interface, which induced numerous and strong signals. Ice propagation velocities were estimated via AE (during the first phase) and infrared thermography. Acoustic activity ceased before the second phase probably because the exothermal heating and the volume expansion of ice caused decreasing tensions. Results indicate cavitation events at the ice front leading to AE. Ultrasonic emission analysis enabled new insights into the complex process of xylem freezing and might be used to monitor ice propagation in natura.
authors.affiliation: Department of Botany, University of Innsbruck, Sternwartestrasse. 15, A-6020, Innsbruck, Austria.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Charrier
authors.affiliation: Department of Botany, University of Innsbruck, Sternwartestrasse. 15, A-6020, Innsbruck, Austria.
authors.forename: Manuel
authors.initials: M
authors.lastname: Pramsohler
authors.affiliation: INRA, UMR547 PIAF, F-63100, Clermont-Ferrand, France.|Clermont Université, Université Blaise Pascal, UMR547 PIAF, F-63100, Clermont-Ferrand, France.
authors.forename: Katline
authors.initials: K
authors.lastname: Charra-Vaskou
authors.affiliation: INRA, UMR547 PIAF, F-63100, Clermont-Ferrand, France.|Clermont Université, Université Blaise Pascal, UMR547 PIAF, F-63100, Clermont-Ferrand, France.
authors.forename: Marc
authors.initials: M
authors.lastname: Saudreau
authors.affiliation: INRA, UMR547 PIAF, F-63100, Clermont-Ferrand, France.|Clermont Université, Université Blaise Pascal, UMR547 PIAF, F-63100, Clermont-Ferrand, France.
authors.forename: Thierry
authors.initials: T
authors.lastname: Améglio
authors.affiliation: Department of Botany, University of Innsbruck, Sternwartestrasse. 15, A-6020, Innsbruck, Austria.
authors.forename: Gilbert
authors.initials: G
authors.lastname: Neuner
authors.affiliation: Department of Botany, University of Innsbruck, Sternwartestrasse. 15, A-6020, Innsbruck, Austria.
authors.forename: Stefan
authors.initials: S
authors.lastname: Mayr
mesh_terms: D000162:Acoustics; D007053:Ice; D028222:Picea / Q000502:physiology*; D013045:Species Specificity; D013696:Temperature; D014465:Ultrasonics; D014934:Wood / Q000502:physiology; D052584:Xylem / Q000502:physiology*
chemical_list: D007053:Ice
keywords: cavitation; freezing stress; ice nucleation; ice propagation; infrared thermography; nondestructive monitoring; ultrasonic acoustic emissions; xylem