Hydrogen isotopes in assimilates and cellulose, but not in n-alkanes, integrate signals of the plant primary carbon metabolism
- 1Forest Dynamics, Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Zuercherstrasse 111, 8903 Birmensdorf, Switzerland
- 2Department of Earth Sciences, University of Oxford, South Parks Road, Oxford OX1 3AN, UK
- 3Water Protection and Substance Flows, Agroscope, Reckenholzstrasse 191, 8046, Zurich, Switzerland
- 4Institute of Agricultural Sciences, ETH Zurich, Universitaetstrasse 2, 8092 Zurich, Switzerland
- 5Department of Geography, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
Recent studies suggest that isotope ratios of the carbon-bound non-exchangeable hydrogen (δ2H) in plant cellulose and lipids can indicate changes in the primary carbon and energy metabolism; however, systematic investigations are scarce.
Here, we studied δ2H patterns in two different tobacco (N. sylvestris) model systems, where severe changes in the plant primary metabolism were known: 1) along a nitrogen (N) supply gradient and 2) in a starch-less knockout mutant (pgm). Specifically, we measured δ2H of water, bulk soluble sugars, transitory starch, and cellulose in leaves and roots, using a novel hot water vapor equilibration method and TC/EA-IRMS. Besides, we measured δ2H values of leaf n-alkanes with GC-IRMS.
We observed clear δ2H differences in sugars and starch along the N gradient and a 2H-enrichment of both assimilates in pgm compared to a wild type control. The photosynthetic 2H-fractionation between leaf water and sugars/starch reached a maximum of ca. 100‰ in both model systems and was related to changes in concentrations of primary metabolites (e.g. sugars, starch, organic and amino acids), enzymatic activities, gas-exchange, and growth. The signal of the primary carbon metabolism was also visible in δ2H of leaf and root cellulose in both system, but dampened compared to those of sugars and starch. In contrast, the signal was absent in leaf n-alkanes in both systems.
Our results provide the first direct evidence that changes in the primary leaf carbon metabolism are imprinted on δ2H of plant carbohydrates in leaf and roots. The metabolic signal might therefore be reconstructed from plant material of important paleo archives (e.g. tree-ring cellulose, lake sediments) and help to better understand plant-climate interactions. The absence of the signal in δ2H of leaf n-alkanes is surprising and suggests a strong difference in metabolic fluxes between carbohydrates and lipids. Yet, this observation may help to further disentangle the processes shaping hydrogen isotopes in plants.
How to cite: Lehmann, M. M., Schuler, P., Cormier, M.-A., Ghiasi, S., Werner, R. A., Saurer, M., and Wiesenberg, G.: Hydrogen isotopes in assimilates and cellulose, but not in n-alkanes, integrate signals of the plant primary carbon metabolism, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5442, https://doi.org/10.5194/egusphere-egu22-5442, 2022.
