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Research article - Peer-reviewed, 2015

Detecting long-term metabolic shifts using isotopomers: CO2-driven suppression of photorespiration in C-3 plants over the 20th century

Ehlers, Ina; Augusti, Angela; Betson, Tatiana R.; Nilsson, Mats; Marshall, John D; Marshall, John D.; Schleucher, Jürgen


Terrestrial vegetation currently absorbs approximately a third of anthropogenic CO2 emissions, mitigating the rise of atmospheric CO2. However, terrestrial net primary production is highly sensitive to atmospheric CO2 levels and associated climatic changes. In C-3 plants, which dominate terrestrial vegetation, net photosynthesis depends on the ratio between photorespiration and gross photosynthesis. This metabolic flux ratio depends strongly on CO2 levels, but changes in this ratio over the past CO2 rise have not been analyzed experimentally. Combining CO2 manipulation experiments and deuterium NMR, we first establish that the intramolecular deuterium distribution (deuterium isotopomers) of photosynthetic C-3 glucose contains a signal of the photorespiration/photosynthesis ratio. By tracing this isotopomer signal in herbarium samples of natural C-3 vascular plant species, crops, and a Sphagnum moss species, we detect a consistent reduction in the photorespiration/photosynthesis ratio in response to the similar to 100-ppm CO2 increase between similar to 1900 and 2013. No difference was detected in the isotopomer trends between beet sugar samples covering the 20th century and CO2 manipulation experiments, suggesting that photosynthetic metabolism in sugar beet has not acclimated to increasing CO2 over >100 y. This provides observational evidence that the reduction of the photorespiration/photosynthesis ratio was ca. 25%. The Sphagnum results are consistent with the observed positive correlations between peat accumulation rates and photosynthetic rates over the Northern Hemisphere. Our results establish that isotopomers of plant archives contain metabolic information covering centuries. Our data provide direct quantitative information on the "CO2 fertilization" effect over decades, thus addressing a major uncertainty in Earth system models.


isotopomer; acclimation; deuterium; CO2 fertilization; atmospheric change

Published in

Proceedings of the National Academy of Sciences
2015, volume: 112, number: 51, pages: 15585-15590

Authors' information

Ehlers, Ina
Umeå University
Augusti, Angela
Umeå University
Betson, Tatiana R.
Umeå University
Swedish University of Agricultural Sciences, Department of Forest Ecology and Management
Marshall, John D (Marshall, John)
Swedish University of Agricultural Sciences, Department of Forest Ecology and Management
Marshall, John D. (Marshall, John)
University of Idaho
Schleucher, Jürgen
Umeå University

UKÄ Subject classification

Forest Science

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