title: Changes and their possible causes in δ13C of dark-respired CO2 and its putative bulk and soluble sources during maize ontogeny.
abstract: The issues of whether, where, and to what extent carbon isotopic fractionations occur during respiration affect interpretations of plant functions that are important to many disciplines across the natural sciences. Studies of carbon isotopic fractionation during dark respiration in C3 plants have repeatedly shown respired CO2 to be (13)C enriched relative to its bulk leaf sources and (13)C depleted relative to its bulk root sources. Furthermore, two studies showed respired CO2 to become progressively (13)C enriched during leaf ontogeny and (13)C depleted during root ontogeny in C3 legumes. As such data on C4 plants are scarce and contradictory, we investigated apparent respiratory fractionations of carbon and their possible causes in different organs of maize plants during early ontogeny. As in the C3 plants, leaf-respired CO2 was (13)C enriched whereas root-respired CO2 was (13)C depleted relative to their putative sources. In contrast to the findings for C3 plants, however, not only root- but also leaf-respired CO2 became more (13)C depleted during ontogeny. Leaf-respired CO2 was highly (13)C enriched just after light-dark transition but the enrichment rapidly decreased over time in darkness. We conclude that (i) although carbon isotopic fractionations in C4 maize and leguminous C3 crop roots are similar, increasing phosphoenolpyruvate-carboxylase activity during maize ontogeny could have produced the contrast between the progressive (13)C depletion of maize leaf-respired CO2 and (13)C enrichment of C3 leaf-respired CO2 over time, and (ii) in both maize and C3 leaves, highly (13)C enriched leaf-respired CO2 at light-to-dark transition and its rapid decrease during darkness, together with the observed decrease in leaf malate content, may be the result of a transient effect of light-enhanced dark respiration.
authors.affiliation: Ecologie Systématique Evolution, Université Paris-Sud, CNRS, AgroParisTech, Université Paris-Saclay, 91400 Orsay, France jaleh.ghashghaie@u-psud.fr.
authors.forename: Jaleh
authors.initials: J
authors.lastname: Ghashghaie
authors.affiliation: Genomics Research Centre, Council for Agricultural Research and Economics, 29017 Fiorenzuola d'Arda (PC), Italy.
authors.forename: Franz W
authors.initials: FW
authors.lastname: Badeck
authors.affiliation: UMR ECOSYS, INRA, AgroParisTech, Université Paris-Saclay, 78850 Thiverval-Grignon, France.
authors.forename: Cyril
authors.initials: C
authors.lastname: Girardin
authors.affiliation: Ecologie Systématique Evolution, Université Paris-Sud, CNRS, AgroParisTech, Université Paris-Saclay, 91400 Orsay, France.
authors.forename: Christophe
authors.initials: C
authors.lastname: Huignard
authors.affiliation: Ecologie Systématique Evolution, Université Paris-Sud, CNRS, AgroParisTech, Université Paris-Saclay, 91400 Orsay, France.
authors.forename: Zackarie
authors.initials: Z
authors.lastname: Aydinlis
authors.affiliation: Ecologie Systématique Evolution, Université Paris-Sud, CNRS, AgroParisTech, Université Paris-Saclay, 91400 Orsay, France.
authors.forename: Charlotte
authors.initials: C
authors.lastname: Fonteny
authors.affiliation: Université de Lorraine, UMR Ecologie et Ecophysiologie Forestière, 54506 Vandoeuvre-lès-Nancy, France INRA, UMR Ecologie et Ecophysiologie Forestière, 54280 Champenoux, France.
authors.forename: Pierrick
authors.initials: P
authors.lastname: Priault
authors.affiliation: Ecologie Systématique Evolution, Université Paris-Sud, CNRS, AgroParisTech, Université Paris-Saclay, 91400 Orsay, France.
authors.forename: Chantal
authors.initials: C
authors.lastname: Fresneau
authors.affiliation: Institute of Plant Sciences Paris-Saclay, IPS2, CNRS, INRA, Université Paris-Sud, Université Evry, Université Paris-Saclay, 91405 Orsay, France.
authors.forename: Marlène
authors.initials: M
authors.lastname: Lamothe-Sibold
authors.affiliation: Ecologie Systématique Evolution, Université Paris-Sud, CNRS, AgroParisTech, Université Paris-Saclay, 91400 Orsay, France.
authors.forename: Peter
authors.initials: P
authors.lastname: Streb
authors.affiliation: Department of Geography, 1475 Jayhawk Drive, University of Kansas, Lawrence, KS 66045, USA School of Natural Sciences, 5200 North Lake Road, University of California, CA 95343, USA.
authors.forename: Valery J
authors.initials: VJ
authors.lastname: Terwilliger
mesh_terms: D002245:Carbon Dioxide / Q000378:metabolism*; D002247:Carbon Isotopes / Q000378:metabolism; D019069:Cell Respiration / Q000502:physiology; D003624:Darkness; D008027:Light; D008293:Malates / Q000378:metabolism; D018515:Plant Leaves / Q000378:metabolism; D018517:Plant Roots / Q000378:metabolism; D003313:Zea mays / Q000254:growth & development* / Q000378:metabolism
chemical_list: D002247:Carbon Isotopes; D008293:Malates; D002245:Carbon Dioxide; C030298:malic acid
keywords: Carbon isotope discrimination; leaves versus roots; light-enhanced dark respiration; maize; ontogeny; respired CO2.