title: The oxygen isotope enrichment of leaf-exported assimilates--does it always reflect lamina leaf water enrichment?
abstract: The oxygen stable isotope composition of plant organic matter (OM) (particularly of wood and cellulose in the tree ring archive) is valuable in studies of plant-climate interaction, but there is a lack of information on the transfer of the isotope signal from the leaf to heterotrophic tissues. We studied the oxygen isotopic composition and its enrichment above source water of leaf water over diel courses in five tree species covering a broad range of life forms. We tracked the transfer of the isotopic signal to leaf water-soluble OM and further to phloem-transported OM. Observed leaf water evaporative enrichment was consistent with values predicted from mechanistic models taking into account nonsteady-state conditions. While leaf water-soluble OM showed the expected (18)O enrichment in all species, phloem sugars were less enriched than expected from leaf water enrichment in Scots pine (Pinus sylvestris), European larch (Larix decidua) and Alpine ash (Eucalyptus delegatensis). Oxygen atom exchange with nonenriched water during phloem loading and transport, as well as a significant contribution of assimilates from bark photosynthesis, can explain these phloem (18)O enrichment patterns. Our results indicate species-specific uncoupling between the leaf water and the OM oxygen isotope signal, which is important for the interpretation of tree ring data.
authors.affiliation: Leibniz Centre for Agricultural Landscape Research, Institute for Landscape Biogeochemistry, Eberswalderstr. 84, 15374, Müncheberg, Germany.|INRA, UMR 1137 Ecologie et Ecophysiologie Forestières INRA/Université de Lorraine, 54280, Champenoux, France.|Research School of Biology, Australian National University, Building 46, Acton, ACT, 0200, Autralia.
authors.forename: Arthur
authors.initials: A
authors.lastname: Gessler
authors.affiliation: INRA, UMR 1137 Ecologie et Ecophysiologie Forestières INRA/Université de Lorraine, 54280, Champenoux, France.
authors.forename: Elke
authors.initials: E
authors.lastname: Brandes
authors.affiliation: Research School of Biology, Australian National University, Building 46, Acton, ACT, 0200, Autralia.|Faculty of Agriculture and Environment, University of Sydney, Private Bag 4011, Narellan, NSW, 2567, Australia.
authors.forename: Claudia
authors.initials: C
authors.lastname: Keitel
authors.affiliation: Swiss Federal Research Institute WSL, Research Unit Landscape Dynamics, Zürcherstrasse 111, CH-8903, Birmensdorf, Switzerland.
authors.forename: Sonja
authors.initials: S
authors.lastname: Boda
authors.affiliation: Leibniz Centre for Agricultural Landscape Research, Institute for Landscape Biogeochemistry, Eberswalderstr. 84, 15374, Müncheberg, Germany.
authors.forename: Zachary E
authors.initials: ZE
authors.lastname: Kayler
authors.affiliation: INRA, UMR 1137 Ecologie et Ecophysiologie Forestières INRA/Université de Lorraine, 54280, Champenoux, France.
authors.forename: André
authors.initials: A
authors.lastname: Granier
authors.affiliation: Faculty of Agriculture and Environment, University of Sydney, Private Bag 4011, Narellan, NSW, 2567, Australia.
authors.forename: Margaret
authors.initials: M
authors.lastname: Barbour
authors.affiliation: Research School of Biology, Australian National University, Building 46, Acton, ACT, 0200, Autralia.
authors.forename: Graham D
authors.initials: GD
authors.lastname: Farquhar
authors.affiliation: Swiss Federal Research Institute WSL, Research Unit Landscape Dynamics, Zürcherstrasse 111, CH-8903, Birmensdorf, Switzerland.
authors.forename: Kerstin
authors.initials: K
authors.lastname: Treydte
mesh_terms: D001692:Biological Transport; D002241:Carbohydrates / Q000737:chemistry*; D002482:Cellulose / Q000737:chemistry; D057231:Climate Change; D005052:Eucalyptus / Q000737:chemistry / Q000502:physiology; D028221:Larix / Q000737:chemistry / Q000502:physiology; D010100:Oxygen / Q000502:physiology*; D010103:Oxygen Isotopes / Q000737:chemistry*; D052585:Phloem / Q000737:chemistry / Q000502:physiology*; D041605:Pinus sylvestris / Q000737:chemistry / Q000502:physiology; D018515:Plant Leaves / Q000737:chemistry / Q000502:physiology*; D015398:Signal Transduction; D014197:Trees / Q000737:chemistry / Q000502:physiology*; D014867:Water / Q000737:chemistry / Q000502:physiology*; D014934:Wood / Q000737:chemistry / Q000502:physiology
chemical_list: D002241:Carbohydrates; D010103:Oxygen Isotopes; D014867:Water; D002482:Cellulose; D010100:Oxygen
keywords: broadleaf; conifer; diel course; oxygen atom exchange; phloem transport