title: On the 13C/12C isotopic signal of day and night respiration at the mesocosm level.
abstract: While there is currently intense effort to examine the (13)C signal of CO(2) evolved in the dark, less is known on the isotope composition of day-respired CO(2). This lack of knowledge stems from technical difficulties to measure the pure respiratory isotopic signal: day respiration is mixed up with photorespiration, and there is no obvious way to separate photosynthetic fractionation (pure c(i)/c(a) effect) from respiratory effect (production of CO(2) with a different delta(13)C value from that of net-fixed CO(2)) at the ecosystem level. Here, we took advantage of new simple equations, and applied them to sunflower canopies grown under low and high [CO(2)]. We show that whole mesocosm-respired CO(2) is slightly (13)C depleted in the light at the mesocosm level (by 0.2-0.8 per thousand), while it is slightly (13)C enriched in darkness (by 1.5-3.2 per thousand). The turnover of the respiratory carbon pool after labelling appears similar in the light and in the dark, and accordingly, a hierarchical clustering analysis shows a close correlation between the (13)C abundance in day- and night-evolved CO(2). We conclude that the carbon source for respiration is similar in the dark and in the light, but the metabolic pathways associated with CO(2) production may change, thereby explaining the different (12)C/(13)C respiratory fractionations in the light and in the dark.
authors.affiliation: Ecologie Systématique Evolution, Bâtiment 362, Université Paris-Sud 11, 91405 Orsay cedex, Paris, France. guillaume.tcherkez@u-psud.fr
authors.forename: Guillaume
authors.initials: G
authors.lastname: Tcherkez
authors.forename: Rudi
authors.initials: R
authors.lastname: Schäufele
authors.forename: Salvador
authors.initials: S
authors.lastname: Nogués
authors.forename: Clément
authors.initials: C
authors.lastname: Piel
authors.forename: Arnoud
authors.initials: A
authors.lastname: Boom
authors.forename: Gary
authors.initials: G
authors.lastname: Lanigan
authors.forename: Cécile
authors.initials: C
authors.lastname: Barbaroux
authors.forename: Catarina
authors.initials: C
authors.lastname: Mata
authors.forename: Sliman
authors.initials: S
authors.lastname: Elhani
authors.forename: Debbie
authors.initials: D
authors.lastname: Hemming
authors.forename: Christina
authors.initials: C
authors.lastname: Maguas
authors.forename: Dan
authors.initials: D
authors.lastname: Yakir
authors.forename: Franz W
authors.initials: FW
authors.lastname: Badeck
authors.forename: Howard
authors.initials: H
authors.lastname: Griffiths
authors.forename: Hans
authors.initials: H
authors.lastname: Schnyder
authors.forename: Jaleh
authors.initials: J
authors.lastname: Ghashghaie
mesh_terms: D002245:Carbon Dioxide / Q000378:metabolism; D002247:Carbon Isotopes; D019069:Cell Respiration; D002940:Circadian Rhythm / Q000502:physiology*; D016000:Cluster Analysis; D003624:Darkness; D006368:Helianthus / Q000378:metabolism*; D007553:Isotope Labeling; D008027:Light; D009928:Organ Specificity; D010788:Photosynthesis; D013997:Time Factors
chemical_list: D002247:Carbon Isotopes; D002245:Carbon Dioxide