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First published online September 17, 2004; 10.1104/pp.104.048470 Plant Physiology 136:3245-3254 (2004) © 2004 American Society of Plant Biologists Respiratory Carbon Metabolism following Illumination in Intact French Bean Leaves Using 13C/12C Isotope Labeling1Laboratoire d'Écophysiologie Végétale, Unité Mixte de Recherche 8079, Université de Paris XI, 91405 Orsay, France
The origin of the carbon atoms in the CO2 respired by French bean (Phaseolus vulgaris) leaves in the dark has been studied using 13C/12C isotopes as tracers. The stable isotope labeling was achieved through a technical device that uses an open gas-exchange system coupled online to an elemental analyzer and linked to an isotope ratio mass spectrometer. The isotopic analysis of the CO2 respired in the dark after a light period revealed that the CO2 was labeled, but the labeling level decreased progressively as the dark period increased. The pattern of disappearance depended on the amount of carbon fixed during the labeling and indicated that there were several pools of respiratory metabolites with distinct turnover rates. We demonstrate that the carbon recently assimilated during photosynthesis accounts for less than 50% of the carbon in the CO2 lost by dark respiration and that the proportion is not influenced by leaf starvation in darkness before the labeling. Therefore, most of the carbon released by dark respiration after illumination does not come from new photosynthates.
1 This work was supported by the European Community's Human Potential Program (contract no. HPRNCT199900059, NETCARB, to S.N.). 2 Present address: Laboratori de Fisiologia Vegetal, Universitat de Barcelona, E08028 Barcelona, Spain. Article, publication date, and citation information can be found at www.plantphysiol.org/cgi/doi/10.1104/pp.104.048470. * Corresponding author; e-mail salvador.nogues{at}ese.u-psud.fr; fax 33169157238. Received June 20, 2004; returned for revision July 27, 2004; accepted July 29, 2004. This article has been cited by other articles:
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