title: Respiratory carbon metabolism in the high mountain plant species Ranunculus glacialis.
abstract: Very little is known about the primary carbon metabolism of the high mountain plant Ranunculus glacialis. It is a species with C3 photosynthesis, but with exceptionally high malate content in its leaves, the biological significance of which remains unclear. 13C/12C-isotope ratio mass spectrometry (IRMS) and 13C-nuclear magnetic resonance (NMR) labelling were used to study the carbon metabolism of R. glacialis, paying special attention to respiration. Although leaf dark respiration was high, the temperature response had a Q10 of 2, and the respiratory quotient (CO2 produced divided by O2 consumed) was nearly 1, indicating that the respiratory pool is comprised of carbohydrates. Malate, which may be a large carbon substrate, was not respired. However, when CO2 fixed by photosynthesis was labelled, little labelling of the CO2 subsequently respired in the dark was detected, indicating that: (i) most of the carbon recently assimilated during photosynthesis is not respired in the dark; and (ii) the carbon used for respiration originates from (unlabelled) reserves. This is the first demonstration of such a low metabolic coupling of assimilated and respired carbon in leaves. The biological significance of the uncoupling between assimilation and respiration is discussed.
authors.affiliation: Station Alpine Joseph Fourier, UMS UJF CNRS 2925-Col du Lautaret, 05480 Villar d'Arène, France. salvador.nogues@ub.edu
authors.forename: Salvador
authors.initials: S
authors.lastname: Nogués
authors.forename: Guillaume
authors.initials: G
authors.lastname: Tcherkez
authors.forename: Peter
authors.initials: P
authors.lastname: Streb
authors.forename: Antoni
authors.initials: A
authors.lastname: Pardo
authors.forename: Florence
authors.initials: F
authors.lastname: Baptist
authors.forename: Richard
authors.initials: R
authors.lastname: Bligny
authors.forename: Jaleh
authors.initials: J
authors.lastname: Ghashghaie
authors.forename: Gabriel
authors.initials: G
authors.lastname: Cornic
mesh_terms: D002244:Carbon / Q000378:metabolism*; D002245:Carbon Dioxide / Q000378:metabolism; D004579:Electron Transport / Q000502:physiology; D008293:Malates / Q000378:metabolism; D019906:Nuclear Magnetic Resonance, Biomolecular; D010788:Photosynthesis; D018515:Plant Leaves / Q000378:metabolism / Q000502:physiology; D031947:Ranunculus / Q000378:metabolism* / Q000502:physiology; D013696:Temperature
chemical_list: D008293:Malates; D002245:Carbon Dioxide; D002244:Carbon; C030298:malic acid