Respiratory carbon metabolism in the high mountain plant species Ranunculus glacialis.
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.
Nogués
Salvador
S
Station Alpine Joseph Fourier, UMS UJF CNRS 2925-Col du Lautaret, 05480 Villar d'Arène, France. salvador.nogues@ub.edu
Tcherkez
Guillaume
G
Streb
Peter
P
Pardo
Antoni
A
Baptist
Florence
F
Bligny
Richard
R
Ghashghaie
Jaleh
J
Cornic
Gabriel
G
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
D008293:Malates; D002245:Carbon Dioxide; D002244:Carbon; C030298:malic acid