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| Titel |
Tracing CO2 fluxes and plant volatile organic compound emissions by stable isotopes |
| VerfasserIn |
Christiane Werner, Frederik Wegener, Kolby Jardine |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250094260
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| Publikation (Nr.) |
 EGU/EGU2014-9662.pdf |
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| Zusammenfassung |
| Plant metabolic processes exert a large influence on global climate and air quality through the
emission of the greenhouse gas CO2 and volatile organic compounds (VOCs). Despite the
enormous importance, processes controlling plant carbon allocation into primary and
secondary metabolism, such as respiratory CO2 emission and VOC synthesis, remains
unclear.
The vegetation exerts a large isotopic imprint on the atmosphere through both,
photosynthetic carbon isotope discrimination and fractionation during respiratory CO2
release (δ13Cres). While the former is well understood, many processes driving carbon
isotope fractionation during respiration are unknown1. There are striking differences in
variations of δ13Cres between plant functional groups, which have been proposed to be
related to carbon partitioning in the metabolic branching points of the respiratory pathways
and secondary metabolism, which are linked via a number of interfaces including the central
metabolite pyruvate2. Notably, it is a known substrate in a large array of secondary pathways
leading to the biosynthesis of many volatile organic compounds (VOCs), such as volatile
isoprenoids, oxygenated VOCs, aromatics, fatty acid oxidation products, which can be
emitted by plants.
Here we investigate if carbon isotope fractionation in light and dark respired CO2 is
associated with VOC emissions in the atmosphere. Specifically, we hypothesize that a high
carbon flux through the pyruvate into various VOC synthesis pathways is associated with a
pronounced 13C-enrichment of respired CO2 above the putative substrate, as it involves the
decarboxylation of the 13C-enriched C-1 from pyruvate.
Based on simultaneous real-time measurements of stable carbon isotope composition of
branch respired CO2 (CRDS) and VOC fluxes (PTR-MS) we traced carbon flow into these
pathways by pyruvate positional labeling.
We demonstrated that in a Mediterranean shrub the 13C-enriched C-1 from
pyruvate is released in substantial amounts as CO2 in the light. Simultaneously,
naturally 13C depleted C-2 and C-3 carbon atoms of the acetyl-moiety are emitted as a
variety of VOCs. Moreover, during light-dark transitions leaf emission bursts of
the oxygenated metabolite acetaldehyde were observed as part of the PDH bypass
pathway in the cytosol2. This may be a new piece of evidence for the origin of
13C-enriched δ13CO2 which is released during Light-Enhanced Dark Respiration
(LEDR).
Our study provides the first evidence that the isotopic signature of respired CO2 is closely
linked to carbon partitioning between anabolic and catabolic pathways and plants strategies
of carbon investment into secondary compound synthesis.
Werner C. & Gessler A. (2011) Diel variations in the carbon isotope composition
of respired CO2 and associated carbon sources: a review of dynamics and
mechanisms. Biogeosciences 8, 2437–2459
Jardine K, Wegener F, Abrell L, vonHaren J, Werner C (2014) Phytogenic
biosynthesis and emission of methyl acetate. PCE 37, 414–424. |
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