title: On the metabolic origin of the carbon isotope composition of CO2 evolved from darkened light-acclimated leaves in Ricinus communis.
abstract: The (13)C isotopic signature (delta(13)C) of CO(2) respired from plants is widely used to assess carbon fluxes and ecosystem functioning. There is, however, a lack of knowledge of the metabolic basis of the delta(13)C value of respired CO(2). To elucidate the physiological mechanisms driving (12)C/(13)C fractionation during respiration, the delta(13)C of respired CO(2) from dark-acclimated leaves during the night, from darkened leaves during the light period, and from stems and roots of Ricinus communis was analysed. The delta(13)C of potential respiratory substrates, the respiratory quotient and the activities of phosphoenolpyruvatecarboxylase (PEPc) and key respiratory enzymes were also measured. It is shown here that the CO(2) evolved from darkened light-acclimated leaves during the light period is (13)C-enriched, and that this correlates with malate accumulation in the light and rapid malate decarboxylation just after the onset of darkness. Whilst CO(2) evolved from leaves was generally (13)C-enriched (but to a lesser extent during the night), CO(2) evolved from stems and roots was depleted compared with the putative respiratory substrates; the difference was mainly caused by intensive PEPc-catalysed CO(2) refixation in stems and roots. These results provide a physiological explanation for short-term variations of delta(13)C in CO(2), illustrating the effects of variations of metabolic fluxes through different biochemical pathways.
authors.affiliation: Environmental Biology Group; Research School of Biological Sciences, Australian National University, GPO Box 475, Canberra, ACT 2601, Australia;School of Forest and Ecosystem Science, University of Melbourne, Water Street, Creswick, VIC 3363, Australia;Institute of Forest Botany and Tree Physiology, Albert-Ludwigs Universität Freiburg, Georges-Köhler-Allee 53/54, 79110 Freiburg, Germany;Laboratoire d'Ecologie, Systématique et Evolution, Département d'Ecophysiologie Végétale, CNRS-UMR 8079, Centre scientifique d'Orsay, Bâtiment 362, Université Paris-Sud XI, 91405 Orsay Cedex, France;Plateforme Métabolisme-Métabolome IFR87, Centre scientifique d'Orsay, Bâtiment 630, Université Paris-Sud XI, 91405 Orsay Cedex, France;Present address: Core Facility Metabolomics, Centre for System Biology (ZBSA), Albert-Ludwigs Universität Freiburg, Habsburgerstr. 49, 79104 Freiburg, Germany.
authors.forename: Arthur
authors.initials: A
authors.lastname: Gessler
authors.affiliation: Environmental Biology Group; Research School of Biological Sciences, Australian National University, GPO Box 475, Canberra, ACT 2601, Australia;School of Forest and Ecosystem Science, University of Melbourne, Water Street, Creswick, VIC 3363, Australia;Institute of Forest Botany and Tree Physiology, Albert-Ludwigs Universität Freiburg, Georges-Köhler-Allee 53/54, 79110 Freiburg, Germany;Laboratoire d'Ecologie, Systématique et Evolution, Département d'Ecophysiologie Végétale, CNRS-UMR 8079, Centre scientifique d'Orsay, Bâtiment 362, Université Paris-Sud XI, 91405 Orsay Cedex, France;Plateforme Métabolisme-Métabolome IFR87, Centre scientifique d'Orsay, Bâtiment 630, Université Paris-Sud XI, 91405 Orsay Cedex, France;Present address: Core Facility Metabolomics, Centre for System Biology (ZBSA), Albert-Ludwigs Universität Freiburg, Habsburgerstr. 49, 79104 Freiburg, Germany.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Tcherkez
authors.affiliation: Environmental Biology Group; Research School of Biological Sciences, Australian National University, GPO Box 475, Canberra, ACT 2601, Australia;School of Forest and Ecosystem Science, University of Melbourne, Water Street, Creswick, VIC 3363, Australia;Institute of Forest Botany and Tree Physiology, Albert-Ludwigs Universität Freiburg, Georges-Köhler-Allee 53/54, 79110 Freiburg, Germany;Laboratoire d'Ecologie, Systématique et Evolution, Département d'Ecophysiologie Végétale, CNRS-UMR 8079, Centre scientifique d'Orsay, Bâtiment 362, Université Paris-Sud XI, 91405 Orsay Cedex, France;Plateforme Métabolisme-Métabolome IFR87, Centre scientifique d'Orsay, Bâtiment 630, Université Paris-Sud XI, 91405 Orsay Cedex, France;Present address: Core Facility Metabolomics, Centre for System Biology (ZBSA), Albert-Ludwigs Universität Freiburg, Habsburgerstr. 49, 79104 Freiburg, Germany.
authors.forename: Oka
authors.initials: O
authors.lastname: Karyanto
authors.affiliation: Environmental Biology Group; Research School of Biological Sciences, Australian National University, GPO Box 475, Canberra, ACT 2601, Australia;School of Forest and Ecosystem Science, University of Melbourne, Water Street, Creswick, VIC 3363, Australia;Institute of Forest Botany and Tree Physiology, Albert-Ludwigs Universität Freiburg, Georges-Köhler-Allee 53/54, 79110 Freiburg, Germany;Laboratoire d'Ecologie, Systématique et Evolution, Département d'Ecophysiologie Végétale, CNRS-UMR 8079, Centre scientifique d'Orsay, Bâtiment 362, Université Paris-Sud XI, 91405 Orsay Cedex, France;Plateforme Métabolisme-Métabolome IFR87, Centre scientifique d'Orsay, Bâtiment 630, Université Paris-Sud XI, 91405 Orsay Cedex, France;Present address: Core Facility Metabolomics, Centre for System Biology (ZBSA), Albert-Ludwigs Universität Freiburg, Habsburgerstr. 49, 79104 Freiburg, Germany.
authors.forename: Claudia
authors.initials: C
authors.lastname: Keitel
authors.affiliation: Environmental Biology Group; Research School of Biological Sciences, Australian National University, GPO Box 475, Canberra, ACT 2601, Australia;School of Forest and Ecosystem Science, University of Melbourne, Water Street, Creswick, VIC 3363, Australia;Institute of Forest Botany and Tree Physiology, Albert-Ludwigs Universität Freiburg, Georges-Köhler-Allee 53/54, 79110 Freiburg, Germany;Laboratoire d'Ecologie, Systématique et Evolution, Département d'Ecophysiologie Végétale, CNRS-UMR 8079, Centre scientifique d'Orsay, Bâtiment 362, Université Paris-Sud XI, 91405 Orsay Cedex, France;Plateforme Métabolisme-Métabolome IFR87, Centre scientifique d'Orsay, Bâtiment 630, Université Paris-Sud XI, 91405 Orsay Cedex, France;Present address: Core Facility Metabolomics, Centre for System Biology (ZBSA), Albert-Ludwigs Universität Freiburg, Habsburgerstr. 49, 79104 Freiburg, Germany.
authors.forename: Juan Pedro
authors.initials: JP
authors.lastname: Ferrio
authors.affiliation: Environmental Biology Group; Research School of Biological Sciences, Australian National University, GPO Box 475, Canberra, ACT 2601, Australia;School of Forest and Ecosystem Science, University of Melbourne, Water Street, Creswick, VIC 3363, Australia;Institute of Forest Botany and Tree Physiology, Albert-Ludwigs Universität Freiburg, Georges-Köhler-Allee 53/54, 79110 Freiburg, Germany;Laboratoire d'Ecologie, Systématique et Evolution, Département d'Ecophysiologie Végétale, CNRS-UMR 8079, Centre scientifique d'Orsay, Bâtiment 362, Université Paris-Sud XI, 91405 Orsay Cedex, France;Plateforme Métabolisme-Métabolome IFR87, Centre scientifique d'Orsay, Bâtiment 630, Université Paris-Sud XI, 91405 Orsay Cedex, France;Present address: Core Facility Metabolomics, Centre for System Biology (ZBSA), Albert-Ludwigs Universität Freiburg, Habsburgerstr. 49, 79104 Freiburg, Germany.
authors.forename: Jaleh
authors.initials: J
authors.lastname: Ghashghaie
authors.affiliation: Environmental Biology Group; Research School of Biological Sciences, Australian National University, GPO Box 475, Canberra, ACT 2601, Australia;School of Forest and Ecosystem Science, University of Melbourne, Water Street, Creswick, VIC 3363, Australia;Institute of Forest Botany and Tree Physiology, Albert-Ludwigs Universität Freiburg, Georges-Köhler-Allee 53/54, 79110 Freiburg, Germany;Laboratoire d'Ecologie, Systématique et Evolution, Département d'Ecophysiologie Végétale, CNRS-UMR 8079, Centre scientifique d'Orsay, Bâtiment 362, Université Paris-Sud XI, 91405 Orsay Cedex, France;Plateforme Métabolisme-Métabolome IFR87, Centre scientifique d'Orsay, Bâtiment 630, Université Paris-Sud XI, 91405 Orsay Cedex, France;Present address: Core Facility Metabolomics, Centre for System Biology (ZBSA), Albert-Ludwigs Universität Freiburg, Habsburgerstr. 49, 79104 Freiburg, Germany.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Kreuzwieser
authors.affiliation: Environmental Biology Group; Research School of Biological Sciences, Australian National University, GPO Box 475, Canberra, ACT 2601, Australia;School of Forest and Ecosystem Science, University of Melbourne, Water Street, Creswick, VIC 3363, Australia;Institute of Forest Botany and Tree Physiology, Albert-Ludwigs Universität Freiburg, Georges-Köhler-Allee 53/54, 79110 Freiburg, Germany;Laboratoire d'Ecologie, Systématique et Evolution, Département d'Ecophysiologie Végétale, CNRS-UMR 8079, Centre scientifique d'Orsay, Bâtiment 362, Université Paris-Sud XI, 91405 Orsay Cedex, France;Plateforme Métabolisme-Métabolome IFR87, Centre scientifique d'Orsay, Bâtiment 630, Université Paris-Sud XI, 91405 Orsay Cedex, France;Present address: Core Facility Metabolomics, Centre for System Biology (ZBSA), Albert-Ludwigs Universität Freiburg, Habsburgerstr. 49, 79104 Freiburg, Germany.
authors.forename: Graham D
authors.initials: GD
authors.lastname: Farquhar
mesh_terms: D000064:Acclimatization; D002245:Carbon Dioxide / Q000737:chemistry / Q000378:metabolism*; D002247:Carbon Isotopes / Q000032:analysis / Q000378:metabolism*; D019069:Cell Respiration / Q000502:physiology*; D003624:Darkness; D010730:Phosphoenolpyruvate Carboxylase / Q000378:metabolism; D018515:Plant Leaves / Q000378:metabolism*; D012278:Ricinus / Q000378:metabolism*
chemical_list: D002247:Carbon Isotopes; D002245:Carbon Dioxide; D010730:Phosphoenolpyruvate Carboxylase