title: Using amino-nitrogen pools and fluxes to identify contributions of understory Acacia spp. to overstory Eucalyptus regnans and stand nitrogen uptake in temperate Australia.
abstract: Amino acid concentration and composition in xylem and phloem sap and in plant tissues are good markers of plant performance and general plant nitrogen (N)-supply. Here, we tested if amino acid pools in Eucalyptus regnans, growing in southeastern Australia were increased by understory acacias in 70-yr-old stands, and if xylem N-transport of temperate Acacia spp. differs from their tropical counterparts. We analysed amino-N concentrations and composition in foliage, xylem and phloem. In a novel approach we coupled amino-N concentrations of xylem with long-term sap flow measurements to calculate total stand N-transport. Xylem N-transport of E. regnans is largely based on amino compounds of the glutamate group (more than 90%). By contrast, Acacia spp. transport mainly aspartate group amino acids in xylem (up to 80%). Amino compound diversity and concentration in tissues and xylem and phloem sap were universally greater in acacias compared to eucalypts. Acacias investigated here can be classified as 'amide transporters'. We conclude that N-status and growth potential of aging E. regnans forest is not enhanced by a contribution of N from understory acacias, and that xylem N-transport in temperate Acacia spp. differs from acacias located in the tropics.
authors.affiliation: Faculty for Agriculture, Food and Natural Resources, University of Sydney, 2006 NSW, Australia.|Chair of Tree Physiology, Institute of Forest Botany and Tree Physiology, Albert-Ludwigs University, Georges-Koehler-Allee 53/54, D-79110 Freiburg, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Pfautsch
authors.affiliation: Core Facility Metabolomics, Centre for System Biology (ZBSA), Albert-Ludwigs University, Habsburgerstrasse 49, D-79104 Freiburg, Germany.|Chair of Tree Physiology, Institute of Forest Botany and Tree Physiology, Albert-Ludwigs University, Georges-Koehler-Allee 53/54, D-79110 Freiburg, Germany.
authors.forename: Arthur
authors.initials: A
authors.lastname: Gessler
authors.affiliation: Faculty for Agriculture, Food and Natural Resources, University of Sydney, 2006 NSW, Australia.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Adams
authors.affiliation: Chair of Tree Physiology, Institute of Forest Botany and Tree Physiology, Albert-Ludwigs University, Georges-Koehler-Allee 53/54, D-79110 Freiburg, Germany.
authors.forename: Heinz
authors.initials: H
authors.lastname: Rennenberg
mesh_terms: D000045:Acacia / Q000378:metabolism*; D000596:Amino Acids / Q000378:metabolism*; D001224:Aspartic Acid / Q000378:metabolism; D001692:Biological Transport; D002980:Climate; D017753:Ecosystem; D005052:Eucalyptus / Q000378:metabolism*; D018698:Glutamic Acid / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism*; D052585:Phloem / Q000378:metabolism; D018515:Plant Leaves / Q000378:metabolism; D018514:Plant Structures / Q000378:metabolism*; D014197:Trees / Q000378:metabolism*; D052584:Xylem / Q000378:metabolism
chemical_list: D000596:Amino Acids; D001224:Aspartic Acid; D018698:Glutamic Acid; D009584:Nitrogen