Biochemical and biophysical drivers of the hydrogen isotopic composition of carbohydrates and acetogenic lipids.

The hydrogen isotopic composition (δH) of plant compounds is increasingly used as a hydroclimatic proxy; however, the interpretation of δH values is hampered by potential coeffecting biochemical and biophysical processes. Here, we studied δH values of water and carbohydrates in leaves and roots, and of leaf -alkanes, in two distinct tobacco () experiments. Large differences in plant performance and biochemistry resulted from (a) soil fertilization with varying nitrogen (N) species ratios and (b) knockout-induced starch deficiency.

Deuterium in marine organic biomarkers: toward a new tool for quantifying aquatic mixotrophy.

The traditional separation between primary producers (autotrophs) and consumers (heterotrophs) at the base of the marine food web is being increasingly replaced by the paradigm that mixoplankton, planktonic protists with the nutritional ability to use both phago(hetero)trophy and photo(auto)trophy to access energy are widespread globally. Thus, many 'phytoplankton' eat, while 50% of 'protozooplankton' also perform photosynthesis. Mixotrophy may enhance primary production, biomass transfer to higher trophic levels and the efficiency of the biological pump to sequester atmospheric CO into the deep ocean.

A high-temperature water vapor equilibration method to determine non-exchangeable hydrogen isotope ratios of sugar, starch and cellulose.

The analysis of the non-exchangeable hydrogen isotope ratio (δ H ) in carbohydrates is mostly limited to the structural component cellulose, while simple high-throughput methods for δ H values of non-structural carbohydrates (NSC) such as sugar and starch do not yet exist. Here, we tested if the hot vapor equilibration method originally developed for cellulose is applicable for NSC, verified by comparison with the traditional nitration method. We set up a detailed analytical protocol and applied the method to plant extracts of leaves from species with different photosynthetic pathways (i.

Influence of starch deficiency on photosynthetic and post-photosynthetic carbon isotope fractionations.

Carbon isotope (13C) fractionations occurring during and after photosynthetic CO2 fixation shape the carbon isotope composition (δ13C) of plant material and respired CO2. However, responses of 13C fractionations to diel variation in starch metabolism in the leaf are not fully understood. Here we measured δ13C of organic matter (δ13COM), concentrations and δ13C of potential respiratory substrates, δ13C of dark-respired CO2 (δ13CR), and gas exchange in leaves of starch-deficient plastidial phosphoglucomutase (pgm) mutants and wild-type plants of four species (Arabidopsis thaliana, Mesembryanthemum crystallinum, Nicotiana sylvestris, and Pisum sativum).

H-fractionations during the biosynthesis of carbohydrates and lipids imprint a metabolic signal on the δ H values of plant organic compounds.

Hydrogen (H) isotope ratio (δ H) analyses of plant organic compounds have been applied to assess ecohydrological processes in the environment despite a large part of the δ H variability observed in plant compounds not being fully elucidated. We present a conceptual biochemical model based on empirical H isotope data that we generated in two complementary experiments that clarifies a large part of the unexplained variability in the δ H values of plant organic compounds. The experiments demonstrate that information recorded in the δ H values of plant organic compounds goes beyond hydrological signals and can also contain important information on the carbon and energy metabolism of plants.