title: Vulnerability to cavitation differs between current-year and older xylem: non-destructive observation with a compact magnetic resonance imaging system of two deciduous diffuse-porous species.
abstract: Development of xylem embolism during water stress in two diffuse-porous hardwoods, Katsura (Cercidiphyllum japonicum) and Japanese white birch (Betula platyphylla var. japonica), was observed non-destructively under a compact magnetic resonance imaging (MRI) system in addition to conventional quantitation of hydraulic vulnerability to cavitation from excised stem segments. Distribution of white and dark areas in MR images corresponded well to the distribution of water-filled/embolized vessels observed by cryo-scanning electron microscopy in both species. Water-filled vessels were observed in MR images as white areas in Katsura and as white dots in Japanese white birch, respectively, and embolisms could be detected as a change to dark areas. The increase in the relative embolized area (REA: %) in the cross-sectional area of total xylem during water stress, which was estimated from the binarized MR images, was consistent with the hydraulic vulnerability curves of these species. From the non-destructive MRI observations, cavitation induced by water stress was shown to develop earlier in 1- or 2-year-old xylem than in the current-year xylem in both species; that is, the vulnerability to cavitation differs between vessels in the current-year xylem and those in older annual rings.
authors: Department of Natural Environmental Studies, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, 277-8563, Japan.
authors: Kenji
authors: K
authors: Fukuda
authors: Department of Natural Environmental Studies, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, 277-8563, Japan.
authors: Daichi
authors: D
authors: Kawaguchi
authors: Graduate School of Environmental and Life Science, Okayama University, Okayama, 700-8530, Japan.
authors: Tomo
authors: T
authors: Aihara
authors: Department of Natural Environmental Studies, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, 277-8563, Japan.
authors: Mayumi Y
authors: MY
authors: Ogasa
authors: Graduate School of Environmental and Life Science, Okayama University, Okayama, 700-8530, Japan.
authors: Naoko H
authors: NH
authors: Miki
authors: MR Technology, Inc., Tsukuba, 305-8573, Japan.
authors: Tomoyuki
authors: T
authors: Haishi
authors: Department of Natural Environmental Studies, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, 277-8563, Japan.
authors: Toshihiro
authors: T
authors: Umebayashi
mesh_terms: D029662:Betula / Q000502:physiology* / Q000648:ultrastructure; D003681:Dehydration; D008279:Magnetic Resonance Imaging / Q000379:methods*; D019684:Magnoliopsida / Q000502:physiology* / Q000648:ultrastructure; D018547:Plant Stems / Q000502:physiology / Q000648:ultrastructure; D016062:Porosity; D014867:Water / Q000502:physiology; D052584:Xylem / Q000502:physiology* / Q000648:ultrastructure
chemical_list: D014867:Water
keywords: MRI; annual ring; drought; embolism; water relations; xylem transport