title: Visualisation by high resolution synchrotron X-ray phase contrast micro-tomography of gas films on submerged superhydrophobic leaves.
abstract: Floods can completely submerge terrestrial plants but some wetland species can sustain O2 and CO2 exchange with the environment via gas films forming on superhydrophobic leaf surfaces. We used high resolution synchrotron X-ray phase contrast micro-tomography in a novel approach to visualise gas films on submerged leaves of common cordgrass (Spartina anglica). 3D tomograms enabled a hitherto unmatched level of detail regarding the micro-topography of leaf gas films. Gas films formed only on the superhydrophobic adaxial leaf side (water droplet contact angle, Φ=162°) but not on the abaxial side (Φ=135°). The adaxial side of the leaves of common cordgrass is plicate with a longitudinal system of parallel grooves and ridges and the vast majority of the gas film volume was found in large ∼180μm deep elongated triangular volumes in the grooves and these volumes were connected to each neighbouring groove via a fine network of gas tubules (∼1.7μm diameter) across the ridges. In addition to the gas film retained on the leaf exterior, the X-ray phase contrast micro-tomography also successfully distinguished gas spaces internally in the leaf tissues, and the tissue porosity (gas volume per unit tissue volume) ranged from 6.3% to 20.3% in tip and base leaf segments, respectively. We conclude that X-ray phase contrast micro-tomography is a powerful tool to obtain quantitative data of exterior gas features on biological samples because of the significant difference in electron density between air, biological tissues and water.
authors.affiliation: Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark.
authors.forename: Torsten
authors.initials: T
authors.lastname: Lauridsen
authors.affiliation: Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark.
authors.forename: Kyriaki
authors.initials: K
authors.lastname: Glavina
authors.affiliation: School of Plant Biology, The University of Western Australia, 35 Stirling Highway, Crawley, 6009 WA, Australia.
authors.forename: Timothy David
authors.initials: TD
authors.lastname: Colmer
authors.affiliation: School of Plant Biology, The University of Western Australia, 35 Stirling Highway, Crawley, 6009 WA, Australia; The Freshwater Biological Laboratory, University of Copenhagen, Universitetsparken 4, 3rd Floor, 2100 Copenhagen, Denmark.
authors.forename: Anders
authors.initials: A
authors.lastname: Winkel
authors.affiliation: Laboratory for Macromolecules and Bioimaging, Paul Scherrer Institut, 5232 Villigen PSI, Switzerland; Faculty of Biology and Medicine, University of Lausanne, 1015 Lausanne, Switzerland; Laboratory for Dynamic Imaging, Monash University, 3800 VIC, Australia.
authors.forename: Sarah
authors.initials: S
authors.lastname: Irvine
authors.affiliation: Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark.
authors.forename: Kim
authors.initials: K
authors.lastname: Lefmann
authors.affiliation: Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark.
authors.forename: Robert
authors.initials: R
authors.lastname: Feidenhans'l
authors.affiliation: School of Plant Biology, The University of Western Australia, 35 Stirling Highway, Crawley, 6009 WA, Australia; The Freshwater Biological Laboratory, University of Copenhagen, Universitetsparken 4, 3rd Floor, 2100 Copenhagen, Denmark; Institute of Advanced Studies, The University of Western Australia, 35 Stirling Highway, Crawley, 6009 WA, Australia. Electronic address: opedersen@bio.ku.dk.
authors.forename: Ole
authors.initials: O
authors.lastname: Pedersen
mesh_terms: D002245:Carbon Dioxide / Q000737:chemistry / Q000378:metabolism*; D004777:Environment; D057927:Hydrophobic and Hydrophilic Interactions; D010100:Oxygen / Q000737:chemistry / Q000378:metabolism*; D010788:Photosynthesis; D018515:Plant Leaves / Q000737:chemistry / Q000648:ultrastructure*; D006109:Poaceae / Q000737:chemistry / Q000648:ultrastructure; D017356:Synchrotrons; D014054:Tomography; D014867:Water / Q000737:chemistry; D014965:X-Rays
chemical_list: D014867:Water; D002245:Carbon Dioxide; D010100:Oxygen
keywords: Aerenchyma; Air film; CT scanning; Halophyte; Hydrophobicity; Internal aeration; Leaf gas film; Spartina anglica; Submergence tolerance; Tomogram; Wetland plant; X-ray phase contrast