Carbon Isotope Fractionation in Plant Respiration

Carbon isotopes have long been used to dissect metabolic pathways. More recently, stable isotopes have become an important tool in modeling global fluxes in the biosphere, and notably CO2 isofluxes. The accuracy of these models relies partly on the knowledge of fractionations associated with each individual flux component. This has led to the observation that carbon isotope fractionation occurs during respiration in plants, and exhibits large temporal and spatial variations. Despite important advances in the area, metabolic features underlying such variability remain to be fully elucidated. The present chapter summarizes available data on plant respiratory fractionation, and presents a critical discussion about the metabolic origin of its variation, in the light of recent developments in understanding the compartmentation and plasticity of plant respiration. It emphasizes the need for refining existing frameworks, and points out knowledge gaps that need to be filled so as to achieve a more quantitative modeling of respiratory fractionation.