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| Titel |
Intramolecular stable isotope distributions detect plant metabolic responses on century time scales |
| VerfasserIn |
Jurgen Schleucher, Ina Ehlers, Angela Augusti, Tatiana Betson |
| 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 |
250096751
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| Publikation (Nr.) |
 EGU/EGU2014-12267.pdf |
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| Zusammenfassung |
| Plants respond to environmental changes on a vast range of time scales, and plant gas
exchanges constitute important feedback mechanisms in the global C cycle. Responses on
time scales of decades to centuries are most important for climate models, for prediction of
crop productivity, and for adaptation to climate change. Unfortunately, responses on these
timescale are least understood.
We argue that the knowledge gap on intermediate time scales is due to a lack of adequate
methods that can bridge between short-term manipulative experiments (e.g. FACE) and paleo
research. Manipulative experiments in plant ecophysiology give information on metabolism
on time scales up to years. However, this information cannot be linked to results from
retrospective studies in paleo research, because little metabolic information can be derived
from paleo archives.
Stable isotopes are prominent tools in plant ecophysiology, biogeochemistry and in paleo
research, but in all applications to date, isotope ratios of whole molecules are measured.
However, it is well established that stable isotope abundance varies among intramolecular
groups of biochemical metabolites, that is each so-called "isotopomer" has a distinct
abundance. This intramolecular variation carries information on metabolic regulation, which
can even be traced to individual enzymes (Schleucher et al., Plant, Cell Environ
1999).
Here, we apply intramolecular isotope distributions to study the metabolic response
of plants to increasing atmospheric [CO2] during the past century. Greenhouse
experiments show that the deuterium abundance among the two positions in the
C6H2 group of photosynthetic glucose depends on [CO2] during growth. This is
observed for all plants using C3 photosynthesis, and reflects the metabolic flux
ratio between photorespiration and photosynthesis. Photorespiration is a major
C flux that limits assimilation in C3 plants, which encompass the overwhelming
fraction of terrestrial photosynthesis and the vast majority of crop species. To access
century time scales, we traced this metabolic signal in historic material of two crop
species during the past 100 years and find the same response as predicted from the
greenhouse experiments. This allows estimating how much photorespiration has
been reduced due to the anthropogenic CO2 emission during the 20th century, and
shows that plants have not acclimated to increasing [CO2] during more than 100
generations.
In summary, we demonstrate that metabolic responses of plants to environmental changes
create intramolecular isotope signals. These signals can be identified in manipulation
experiments and can be retrieved from plant archives. The isotope abundance of each
intramolecular position is set by specific isotope fractionations, such as enzyme isotope
effects or hydrogen exchange with xylem water (Augusti et al., Chem. Geol. 2008). Therefore
it may be possible to simultaneously reconstruct several physiologic or climate signals from
an archive of a single molecule.
The principles governing intramolecular isotope distributions are general for all
metabolites and isotopes (D, 13C), therefore intramolecular isotope distributions can multiply
the information content of paleo archives. In particular, they allow extraction of metabolic
information on long time scales, thereby connecting plant physiology with paleo research. |
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