title: Changes in δ(13)C of dark respired CO2 and organic matter of different organs during early ontogeny in peanut plants.
abstract: Carbon isotope composition in respired CO2 and organic matter of individual organs were measured on peanut seedlings during early ontogeny in order to compare fractionation during heterotrophic growth and transition to autotrophy in a species with lipid seed reserves with earlier results obtained on beans. Despite a high lipid content in peanut seeds (48%) compared with bean seeds (1.5%), the isotope composition of leaf- and root-respired CO2 as well as its changes during ontogeny were similar to already published data on bean seedlings: leaf-respired CO2 became (13)C-enriched reaching -21.5‰, while root-respired CO2 became (13)C-depleted reaching around -31‰ at the four-leaf stage. The opposite respiratory fractionation in leaves vs. roots already reported for C3 herbs was thus confirmed for peanuts. However, contrarily to beans, the peanut cotyledon-respired CO2 was markedly (13)C-enriched, and its (13)C-depletion was noted from the two-leaf stage onwards only. Carbohydrate amounts being very low in peanut seeds, this cannot be attributed solely to their use as respiratory substrate. The potential role of isotope fractionation during glyoxylate cycle and/or gluconeogenesis on the (13)C-enriched cotyledon-respired CO2 is discussed.
authors.affiliation: a Laboratoire d'Ecologie, Systématique et Evolution (ESE) , Université de Paris-Sud (XI) , Orsay , France.
authors.forename: Jaleh
authors.initials: J
authors.lastname: Ghashghaie
authors.forename: Franz W
authors.initials: FW
authors.lastname: Badeck
authors.forename: Cyril
authors.initials: C
authors.lastname: Girardin
authors.forename: Diana
authors.initials: D
authors.lastname: Sketriené
authors.forename: Marlène
authors.initials: M
authors.lastname: Lamothe-Sibold
authors.forename: Roland A
authors.initials: RA
authors.lastname: Werner
mesh_terms: D010367:Arachis / Q000254:growth & development / Q000378:metabolism*; D002245:Carbon Dioxide / Q000378:metabolism*; D002247:Carbon Isotopes / Q000032:analysis / Q000378:metabolism; D019069:Cell Respiration; D018548:Cotyledon / Q000378:metabolism*; D018515:Plant Leaves / Q000378:metabolism*; D018517:Plant Roots / Q000378:metabolism*; D036226:Seedlings / Q000254:growth & development / Q000378:metabolism
chemical_list: D002247:Carbon Isotopes; D002245:Carbon Dioxide
keywords: carbon-13; cotyledons; isotope ecology; leaves vs. roots; ontogeny; peanut; plant respiration; respired CO2