The 'photosynthetic C pathway' links carbon assimilation and growth in California poplar.

Although primarily studied in relation to photorespiration, serine metabolism in chloroplasts may play a key role in plant CO fertilization responses by linking CO assimilation with growth. Here, we show that the phosphorylated serine pathway is part of a 'photosynthetic C pathway' and demonstrate its high activity in foliage of a C tree where it rapidly integrates photosynthesis and C metabolism contributing to new biomass via methyl transfer reactions, imparting a large natural C-depleted signature. Using CO-labelling, we show that leaf serine, the S-methyl group of leaf methionine, pectin methyl esters, and the associated methanol released during cell wall expansion during growth, are directly produced from photosynthetically-linked C metabolism, within minutes of light exposure.

Isotopic analysis (δC and δH) of lignin methoxy groups in forest soils to identify and quantify lignin sources.

The relative apportion of above and below ground carbon sources is known to be an important factor in soil organic matter formation. Although lignin is the most abundant aromatic plant material in the terrestrial biosphere, our understanding of lignin source contributions to soil organic matter (SOM) is limited due to the complex molecular structure and analysis of lignin. In this study, we novelly apply the dual isotopic analysis (δC and δH values) of lignin methoxy groups (LMeO) with the Bayesian mixing model, MixSIAR, to apportion lignin sources in two contrasting soil types, a podzol and a stagnosol.

Comparison of Carbon Isotope Ratio Measurement of the Vanillin Methoxy Group by GC-IRMS and C-qNMR.

Site-specific carbon isotope ratio measurements by quantitative C NMR (C-qNMR), Orbitrap-MS, and GC-IRMS offer a new dimension to conventional bulk carbon isotope ratio measurements used in food provenance, forensics, and a number of other applications. While the site-specific measurements of carbon isotope ratios in vanillin by C-qNMR or Orbitrap-MS are powerful new tools in food analysis, there are a limited number of studies regarding the validity of these measurement results. Here we present carbon site-specific measurements of vanillin by GC-IRMS and C-qNMR for methoxy carbon.

Sources and sinks of chloromethane in a salt marsh ecosystem: constraints from concentration and stable isotope measurements of laboratory incubation experiments.

Chloromethane (CHCl) is the most abundant long-lived chlorinated organic compound in the atmosphere and contributes significantly to natural stratospheric ozone depletion. Salt marsh ecosystems including halophyte plants are a known source of atmospheric CHCl but estimates of their total global source strength are highly uncertain and knowledge of the major production and consumption processes in the atmosphere-halophyte-soil system is yet incomplete. In this study we investigated the halophyte plant, Salicornia europaea, and soil samples from a coastal salt marsh site in Sardinia/Italy for their potential to emit and consume CHCl and using flux measurements, stable isotope techniques and Arrhenius plots differentiated between biotic and abiotic processes.

Chlorine Isotope Fractionation of the Major Chloromethane Degradation Processes in the Environment.

Chloromethane (CHCl) is an important source of chlorine in the stratosphere, but detailed knowledge of the magnitude of its sources and sinks is missing. Here, we measured the stable chlorine isotope fractionation (ε) associated with the major abiotic and biotic CHCl sinks in the environment, namely, CHCl degradation by hydroxyl (OH) and chlorine (Cl) radicals in the troposphere and by reference bacteria CM4 and MB2 from terrestrial and marine environments, respectively. No chlorine isotope fractionation was detected for reaction of CHCl with OH and Cl radicals, whereas a large chlorine isotope fractionation (ε) of -10.