Plant-climate interactions have a strong influence on the global carbon cycle. We aim to study those interactions as well as climate variability retrospectively using tree rings, to detect possible acclimation on time scales of centuries. The abundance of the stable hydrogen isotope, deuterium (D) in plant material is influenced both by climate and physiology. The D abundance of precipitation water carries a climate (temperature) signal, which is transferred to plant material. Besides this, transpiration creates a humidity signal, and enzyme isotope effects create physiological signals. Finally, these signals can be modified by hydrogen exchange during cellulose synthesis. If climate and physiological signals can be separated and detected simultaneously, they can be used to infer plant-climate interactions. Among the processes determining the D abundance in plant material, biosynthetic reactions and hydrogen exchange during cellulose synthesis are enzyme-catalyzed processes. Therefore, they affect the D abundance in individual C-H groups, that is, they determine the Deuterium Isotopomer Distribution (DID). Deuterium Nuclear Magnetic Resonance allows measuring the DID. In a D labelling experiment, we have studied hydrogen exchange during cellulose synthesis in oak and spruce trees. Our results show that hydrogen exchange with water is high for the C2-H group of glucose. This means that C2-H acquires the temperature signal present in source water. In a CO2 enrichment experiments, we have investigated relationships between DID and metabolic fluxes of primary C metabolism. We have evidence that the D abundances in the C6-H2 group of glucose reflect the photosynthesis/photorespiration ratio. This has been observed both in leaves and tree rings in manipulative CO2 fumigation experiments but also in a 150 year tree-ring series. We conclude that DID measurements can be used for climate reconstruction from tree rings, and to investigate plant-climate interactions on long-time scales, such as CO2 fertilisation since industrialisation.
Deuterium Isotopomer Distribution: A way to separate climate and physiology in tree-ring cellulose
A Augusti;
2013
Abstract
Plant-climate interactions have a strong influence on the global carbon cycle. We aim to study those interactions as well as climate variability retrospectively using tree rings, to detect possible acclimation on time scales of centuries. The abundance of the stable hydrogen isotope, deuterium (D) in plant material is influenced both by climate and physiology. The D abundance of precipitation water carries a climate (temperature) signal, which is transferred to plant material. Besides this, transpiration creates a humidity signal, and enzyme isotope effects create physiological signals. Finally, these signals can be modified by hydrogen exchange during cellulose synthesis. If climate and physiological signals can be separated and detected simultaneously, they can be used to infer plant-climate interactions. Among the processes determining the D abundance in plant material, biosynthetic reactions and hydrogen exchange during cellulose synthesis are enzyme-catalyzed processes. Therefore, they affect the D abundance in individual C-H groups, that is, they determine the Deuterium Isotopomer Distribution (DID). Deuterium Nuclear Magnetic Resonance allows measuring the DID. In a D labelling experiment, we have studied hydrogen exchange during cellulose synthesis in oak and spruce trees. Our results show that hydrogen exchange with water is high for the C2-H group of glucose. This means that C2-H acquires the temperature signal present in source water. In a CO2 enrichment experiments, we have investigated relationships between DID and metabolic fluxes of primary C metabolism. We have evidence that the D abundances in the C6-H2 group of glucose reflect the photosynthesis/photorespiration ratio. This has been observed both in leaves and tree rings in manipulative CO2 fumigation experiments but also in a 150 year tree-ring series. We conclude that DID measurements can be used for climate reconstruction from tree rings, and to investigate plant-climate interactions on long-time scales, such as CO2 fertilisation since industrialisation.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
