title: The contribution of vascular and extra-vascular water pathways to drought-induced decline of leaf hydraulic conductance.
abstract: Drought stress can impair leaf hydraulic conductance (Kleaf), but the relative contribution of changes in the efficiency of the vein xylem water pathway and in the mesophyll route outside the xylem in driving the decline of Kleaf is still debated. We report direct measurements of dehydration-induced changes in the hydraulic resistance (R=1/K) of whole leaf (Rleaf), as well as of the leaf xylem (Rx) and extra-vascular pathways (Rox) in four Angiosperm species. Rleaf, Rx, and Rox were measured using the vacuum chamber method (VCM). Rleaf values during progressive leaf dehydration were also validated with measurements performed using the rehydration kinetic method (RKM). We analysed correlations between changes in Rx or Rox and Rleaf, as well as between morpho-anatomical traits (including dehydration-induced leaf shrinkage), vulnerability to embolism, and leaf water relation parameters. Measurements revealed that the relative contribution of vascular and extra-vascular hydraulic properties in driving Kleaf decline during dehydration is species-specific. Whilst in two study species the progressive impairment of both vascular and extra-vascular pathways contributed to leaf hydraulic vulnerability, in the other two species the vascular pathway remained substantially unaltered during leaf dehydration, and Kleaf decline was apparently caused only by changes in the hydraulic properties of the extra-vascular compartment.
authors.affiliation: Dipartimento di Scienze Chimiche, Biologiche, Farmaceutiche e Ambientali, Università di Messina, Salita F. Stagno D'Alcontres 31, 98166 Messina, Italy ptrifilo@unime.it.
authors.forename: Patrizia
authors.initials: P
authors.lastname: Trifiló
authors.affiliation: Dipartimento di Scienze Chimiche, Biologiche, Farmaceutiche e Ambientali, Università di Messina, Salita F. Stagno D'Alcontres 31, 98166 Messina, Italy.
authors.forename: Fabio
authors.initials: F
authors.lastname: Raimondo
authors.affiliation: Dipartimento di Scienze della Vita, Università di Trieste, Via L. Giorgieri 10, 34127 Trieste, Italy.
authors.forename: Tadeja
authors.initials: T
authors.lastname: Savi
authors.affiliation: Dipartimento di Scienze Chimiche, Biologiche, Farmaceutiche e Ambientali, Università di Messina, Salita F. Stagno D'Alcontres 31, 98166 Messina, Italy.
authors.forename: Maria A
authors.initials: MA
authors.lastname: Lo Gullo
authors.affiliation: Dipartimento di Scienze della Vita, Università di Trieste, Via L. Giorgieri 10, 34127 Trieste, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Nardini
mesh_terms: D031284:Aleurites / Q000502:physiology; D003681:Dehydration / Q000503:physiopathology; D031566:Magnolia / Q000502:physiology; D018515:Plant Leaves / Q000502:physiology*; D018526:Plant Transpiration / Q000502:physiology; D029963:Quercus / Q000502:physiology; D027843:Vitis / Q000502:physiology; D014867:Water / Q000378:metabolism; D052584:Xylem / Q000502:physiology*
chemical_list: D014867:Water
keywords: Drought; leaf extra-vascular conductance; leaf hydraulic conductance; leaf vein conductance; leaf vulnerability; shrinkage; vulnerability segmentation.