title: Characteristics of ultrasonic acoustic emissions from walnut branches during freeze-thaw-induced embolism formation.
abstract: Ultrasonic acoustic emission (UAE) methods have been applied for the detection of freeze-thaw-induced embolism formation in water conduits of tree species. Until now, however, the exact source(s) of UAE has not been identified especially in angiosperm species, in which xylem tissues are composed of diverse types of cells. In this study, UAE was recorded from excised branches of walnut (Juglans regia cv. Franquette) during freeze-thaw cycles, and attempts were made to characterize UAEs generated by cavitation events leading to embolism formation according to their properties. During freeze-thaw cycles, a large number of UAEs were generated from the sample segments. However, the cumulative numbers of total UAE during freeze-thawing were not correlated with the percentage loss of hydraulic conductivity after thawing, suggesting that the sources of UAE were not only cavitation leading to embolism formation in vessels. Among the UAEs, cumulative numbers of UAEs with absolute energy >10.0 fJ strongly correlated with the increase in percentage loss of hydraulic conductivity. The high absolute energy of the UAEs might reflect the formation of large bubbles in the large lumen of vessels. Therefore, UAEs generated by cavitation events in vessels during freeze-thawing might be distinguished from other signals according to their magnitudes of absolute energy. On the other hand, the freezing of xylem parenchyma cells was followed by a certain number of UAEs. These results indicate the possibility that UAE methods can be applied to the detection of both freeze-thaw-induced embolism and supercooling breakdown in parenchyma cells in xylem.
authors: Institut National de la Recherche Agronomique, UMR 547 PIAF, F-63100 Clermont-Ferrand, France Clermont Université, Université Blaise Pascal, UMR 547 PIAF, F-63100 Clermont-Ferrand, France Department of Agro-Environmental Science, Obihiro University of Agriculture and Veterinary Medicine, Obihiro 080-8555, Japan.
authors: Jun
authors: J
authors: Kasuga
authors: Institut National de la Recherche Agronomique, UMR 547 PIAF, F-63100 Clermont-Ferrand, France Clermont Université, Université Blaise Pascal, UMR 547 PIAF, F-63100 Clermont-Ferrand, France Department of Botany, University of Innsbruck, A-6020 Innsbruck, Austria.
authors: Guillaume
authors: G
authors: Charrier
authors: Cryobiofrontier Research Center, Faculty of Agriculture, Iwate University, Morioka 020-8550, Japan.
authors: Matsuo
authors: http://orcid.org/0000-0003-0436-2976
authors: M
authors: Uemura
authors: Institut National de la Recherche Agronomique, UMR 547 PIAF, F-63100 Clermont-Ferrand, France Clermont Université, Université Blaise Pascal, UMR 547 PIAF, F-63100 Clermont-Ferrand, France Thierry.Ameglio@clermont.inra.fr.
authors: Thierry
authors: T
authors: Améglio
mesh_terms: D005615:Freezing; D031324:Juglans / Q000502:physiology*; D058503:Mesophyll Cells; D018547:Plant Stems / Q000502:physiology; D018526:Plant Transpiration; D013312:Stress, Physiological; D014197:Trees; D014465:Ultrasonics; D014867:Water / Q000502:physiology; D052584:Xylem / Q000502:physiology*
chemical_list: D014867:Water
keywords: Embolism formation; freezing stress; loss of hydraulic conductivity; ultrasonic acoustic emission; vessel; walnut; xylem parenchyma.