Link between plant volatile organic compound (VOC) emissions and CO2 metabolism from sub-molecular to ecosystem scales by 13C-labelling

Biogenic volatile organic compound (BVOC) emissions exert a large influence on the atmosphere. However, processes controlling plant carbon allocation into primary and secondary metabolism, such as photosynthetic carbon uptake, respiratory CO₂ emission and VOC synthesis, remain unclear. De novo synthesis of BVOC depends on the availability of carbon, as well as energy provided by primary metabolism. Thus, carbon allocation may compete between primary and secondary metabolism, which are linked via a number of interfaces including the central metabolite pyruvate. It is the main substrate fulling respiration, but also a substrates for a large array of secondary pathways leading to the biosynthesis of many volatile organic compounds, such as volatile isoprenoids, oxygenated VOCs. Within the European Research Council (ERC) Project VOCO we developed a novel technological basis to couple CO₂ fluxes with VOC emissions based on simultaneous real-time measurements of stable carbon isotope composition of branch respired CO₂ and VOC fluxes (Fasbender et al. 2018). Position specific ¹³C-labeled pyruvate feeding experiments are used to trace partitioning within the metabolic branching points into VOCs versus CO₂ emissions in the light and in the dark, bridging scales from sub-molecular to whole-plant and ecosystem processes. Positional 13C-labelling will trace real-time sub-molecular carbon investment into VOCs and CO₂, enabling mechanistic descriptions of the underlying biochemical pathways coupling anabolic and catabolic processes, particularly the long-overlooked link between secondary compound synthesis and CO2 emission in the light. These fluxes will be traced from the leaves and roots to the ecosystem scale in a whole-ecosystem positional labelling experiment in the tropical rainforest biome of the Biosphere 2 near Tucson, Arizona (B2 WALD campaign), where we will implement a controlled ecosystem drought. This will deliver unique real time data on carbon partitioning from the metabolic to ecosystem scale.

Fasbender L., et al. (2018). A novel approach combining PTR-TOF-MS, ¹³CO₂ laser spectroscopy and ¹³C-metabolite labelling to trace real-time carbon allocation into BVOCs and respiratory CO₂. PLOS One ,13: e0204398