title: Leaf vein xylem conduit diameter influences susceptibility to embolism and hydraulic decline.
abstract: Ecosystems worldwide are facing increasingly severe and prolonged droughts during which hydraulic failure from drought-induced embolism can lead to organ or whole plant death. Understanding the determinants of xylem failure across species is especially critical in leaves, the engines of plant growth. If the vulnerability segmentation hypothesis holds within leaves, higher order veins that are most terminal in the plant hydraulic system should be more susceptible to embolism to protect the rest of the water transport system. Increased vulnerability in the higher order veins would also be consistent with these experiencing the greatest tensions in the plant xylem network. To test this hypothesis, we combined X-ray micro-computed tomography imaging, hydraulic experiments, cross-sectional anatomy and 3D physiological modelling to investigate how embolisms spread throughout petioles and vein orders during leaf dehydration in relation to conduit dimensions. Decline of leaf xylem hydraulic conductance (Kx) during dehydration was driven by embolism initiating in petioles and midribs across all species, and Kxvulnerability was strongly correlated with petiole and midrib conduit dimensions. Our simulations showed no significant impact of conduit collapse on Kxdecline. We found xylem conduit dimensions play a major role in determining the susceptibility of the leaf water transport system during strong leaf dehydration.
authors.affiliation: Department of Ecology and Evolutionary Biology, University of California Los Angeles, 621 Charles E. Young Drive South, Los Angeles, CA, 90095, USA.|Department of Biology, Utah State University, Logan, UT, 84322, USA.
authors.forename: Christine
authors.initials: C
authors.lastname: Scoffoni
authors.affiliation: Department of Viticulture and Enology, University of California, Davis, CA, 95616, USA.
authors.forename: Caetano
authors.initials: C
authors.lastname: Albuquerque
authors.affiliation: School of Forestry & Environmental Studies, Yale University, 195 Prospect Street, New Haven, CT, 06511, USA.
authors.forename: Craig R
authors.initials: CR
authors.lastname: Brodersen
authors.affiliation: Department of Ecology and Evolutionary Biology, University of California Los Angeles, 621 Charles E. Young Drive South, Los Angeles, CA, 90095, USA.
authors.forename: Shatara V
authors.initials: SV
authors.lastname: Townes
authors.affiliation: Department of Ecology and Evolutionary Biology, University of California Los Angeles, 621 Charles E. Young Drive South, Los Angeles, CA, 90095, USA.
authors.forename: Grace P
authors.initials: GP
authors.lastname: John
authors.affiliation: PIAF, INRA, Univ. Clermont-Auvergne, Clermont-Ferrand, 63100, France.
authors.forename: Hervé
authors.initials: H
authors.lastname: Cochard
authors.affiliation: Plant Breeding Institute, Faculty of Agriculture and Environment, The University of Sydney, 12656 Newell Hwy, Narrabri, NSW, 2390, Australia.
authors.forename: Thomas N
authors.initials: TN
authors.lastname: Buckley
authors.affiliation: Department of Viticulture and Enology, University of California, Davis, CA, 95616, USA.|USDA-Agricultural Research Service, Davis, CA, 95616, USA.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: McElrone
authors.affiliation: Department of Ecology and Evolutionary Biology, University of California Los Angeles, 621 Charles E. Young Drive South, Los Angeles, CA, 90095, USA.
authors.forename: Lawren
authors.initials: L
authors.lastname: Sack
mesh_terms: D003198:Computer Simulation; D003681:Dehydration; D021621:Imaging, Three-Dimensional; D008954:Models, Biological; D018515:Plant Leaves / Q000033:anatomy & histology / Q000502:physiology*; D013045:Species Specificity; D014867:Water / Q000502:physiology*; D055114:X-Ray Microtomography; D052584:Xylem / Q000033:anatomy & histology* / Q000502:physiology*
chemical_list: D014867:Water
keywords: cavitation; microCT; percentage loss of conductivity; venation architecture; xylem collapse