| 1. |
- Augusti, Angela, et al.
(författare)
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Deriving correlated climate and physiological signals from deuterium isotopomers in tree rings
- 2008
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Ingår i: Chemical Geology. - : Elsevier BV. - 0009-2541 .- 1872-6836. ; 252:1-2, s. 1-8
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Tidskriftsartikel (refereegranskat)abstract
- he deuterium (D) abundance of tree-ring cellulose archives past climatic conditions, but previous attempts to access this archive have led to conflicting results. Based on an overview of D fractionation mechanisms in plants, we explain why past measurements of D abundance yield unreliable paleo signals. Our data show that variation in D abundance among the C–H groups (isotopomer variation) of tree-ring cellulose is generally greater than variation in D abundance due to climatic influences. A comparison of the D isotopomer abundances of soluble sugars of annual plants and of trees, and of tree-ring cellulose shows that an “isotopomer pattern” of the C3 photosynthetic pathway is transmitted from soluble sugars to tree-ring cellulose. Differences in this pattern between oaks and conifers appear to be related to differences in metabolism. Furthermore, the patterns are modified by hydrogen isotope exchange between C–H groups and source water during cellulose synthesis. Based on these results, we propose a strategy to simultaneously reconstruct climate signals and signals related to tree physiology from D isotopomers of tree rings. Combination of climate signals and physiological signals may allow the detection of century-time-scale adaptations of trees to past environmental change, and help to forecast future adaptations.
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| 2. |
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| 3. |
- Augusti, Angela, et al.
(författare)
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Hydrogen exchange during cellulose synthesis distinguishes climatic and biochemical isotope fractionations in tree rings.
- 2006
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Ingår i: New Phytologist. - : Wiley. - 0028-646X .- 1469-8137. ; 172:3, s. 490-499
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Tidskriftsartikel (refereegranskat)abstract
- • The abundance of the hydrogen isotope deuterium (D) in tree rings is an attractive record of climate; however, use of this record has proved difficult so far, presumably because climatic and physiological influences on D abundance are difficult to distinguish.• Using D labelling, we created a D gradient in trees. Leaf soluble sugars of relatively low D abundance entered cellulose synthesis in stems containing strongly D-labelled water. We used nuclear magnetic resonance (NMR) spectroscopy to quantify D in the C-H groups of leaf glucose and of tree-ring cellulose.• Ratios of D abundances of individual C-H groups of leaf glucose depended only weakly on leaf D labelling, indicating that the D abundance pattern was determined by physiological influences. The D abundance pattern of tree-ring cellulose revealed C-H groups that exchanged strongly (C(2)-H) or weakly (C(6)-H2) with water during cellulose synthesis.• We propose that strongly exchanging C-H groups of tree-ring cellulose adopt a climate signal stemming from the D abundance of source water. C-H groups that exchange weakly retain their D abundance established in leaf glucose, which reflects physiological influences. Combining both types of groups may allow simultaneous reconstruction of climate and physiology from tree rings.
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| 4. |
- Betson, Tatiana R, et al.
(författare)
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Quantification of deuterium isotopomers of tree-ring cellulose using nuclear magnetic resonance.
- 2006
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 78:24, s. 8406-8411
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Tidskriftsartikel (refereegranskat)abstract
- Stable isotopes in tree rings are important tools for reconstruction of past climate. Deuterium (D) is of particular interest since it may contain climate signals and report on tree physiology. Measurements of the D/H ratio of tree-ring cellulose have proven difficult to interpret, presumably because the D/H ratio of the whole molecule blends the abundances of the seven D isotopomers of cellulose. Here we present a method to measure the abundance of the D isotopomers of tree-ring cellulose by nuclear magnetic resonance spectroscopy (NMR). The method transforms tree-ring cellulose into a glucose derivative that gives highly resolved, quantifiable deuterium NMR spectra. General guidelines for measurement of D isotopomers by NMR are described. The transformation was optimized for yield and did not alter the original D isotopomer abundances, thus, conserving the original signals recorded in wood cellulose. In the tree-ring samples tested, the abundances of D isotopomers varied by approximately ±10% (2% standard error). This large variability can only be caused by biochemistry processes and shows that more information is present in D isotopomer abundances, compared to the D/H ratio. Therefore, measurements of the D isotopomer distribution of tree rings may be used to obtain information on long-term adaptations to environmental changes and past climate change.
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| 5. |
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| 6. |
- Ehlers, Ina, et al.
(författare)
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Detecting long-term metabolic shifts using isotopomers : CO2-driven suppression of photorespiration in C-3 plants over the 20th century
- 2015
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 112:51, s. 15585-15590
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 7. |
- Ehlers, Ina, 1984-, et al.
(författare)
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Elucidating Turnover Pathways of Bioactive Small Molecules by Isotopomer Analysis : The Persistent Organic Pollutant DDT
- 2014
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Ingår i: PLOS ONE. - : PLoS ONE. - 1932-6203. ; 9:10, s. e110648-
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Tidskriftsartikel (refereegranskat)abstract
- The persistent organic pollutant DDT (1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane) is still indispensable in the fight againstmalaria, although DDT and related compounds pose toxicological hazards. Technical DDT contains the dichloro congenerDDD (1-chloro-4-[2,2-dichloro-1-(4-chlorophenyl)ethyl]benzene) as by-product, but DDD is also formed by reductive degradation of DDT in the environment. To differentiate between DDD formation pathways, we applied deuterium NMR spectroscopy to measure intramolecular deuterium distributions (2H isotopomer abundances) of DDT and DDD. DDD formed in the technical DDT synthesis was strongly deuterium-enriched at one intramolecular position, which we traced back to 2H/1H fractionation of a chlorination step in the technical synthesis. In contrast, DDD formed by reductive degradation was strongly depleted at the same position, which was due to the incorporation of 2H-depleted hydride equivalents during reductive degradation. Thus, intramolecular isotope distributions give mechanistic information on reaction pathways, and explain a puzzling difference in the whole-molecule 2H/1H ratio between DDT and DDD. In general, our results highlight that intramolecular isotope distributions are essential to interpret whole-molecule isotope ratios. Intramolecular isotope information allows distinguishing pathways of DDD formation, which is important to identify polluters or to assess DDT turnover in the environment. Because intramolecular isotope data directly reflect isotope fractionation of individual chemical reactions, they are broadly applicable to elucidate transformation pathways of smallbioactive molecules in chemistry, physiology and environmental science.
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| 8. |
- Ehlers, Ina, 1984-, et al.
(författare)
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Quantification of a metabolic shift towards photosynthesisin C3 plants driven by 20th-century CO2 rise
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Terrestrial vegetation currently absorbs approximately a third of the annual anthropogenic CO2 emissions, mitigating the rise of atmospheric CO2. However,terrestrial net primary production is highly sensitive to atmospheric [CO2] and associated climatic changes. In C3-plants, which dominate terrestrial vegetation, netphotosynthesis depends on the ratio between gross photosynthesis and photorespiration, which strongly depends on [CO2]. However, our knowledge of feedbacks betweenterrestrial biomes and increasing atmospheric [CO2] is nearly entirely based on atmospheric inversion models and manipulation experiments, which do not reveal physiological mechanisms or are limited in duration and to step increases in [CO2]. By applying novel NMR (Nuclear Magnetic Resonance) spectroscopy methodology we examine isotopomer ratios of plant carbohydrates to probe shifts in the photosynthesis/photorespiration ratio in C3 plants over more than a century. Using herbarium samples of natural vascular plant species, crops and a Sphagnum species, we detect a consistent 35% increase in the 2photosynthesis/photorespiration ratio in responseto the ~100 ppm CO2 increase between approximately 1900 and 2013, with no evidencefor feedback regulation by the plants. Our data provide direct quantitative information on the “CO2 fertilization effect” over century time scales, thus addressing a major uncertainty in Earth system models, enabling improved predictions of the future [CO2] sink strength of terrestrial ecosystems. Further, relating the detected metabolic shift in crop plants to historic yield trends indicates that only a fraction of the increased net photosynthesis has translated into increased yield. Our results also demonstrate that archives of plant material contain metabolic information embedded in their isotopomer ratios covering centuries, bridging a fundamental gap between experimental plant science and paleoenvironmental studies.
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