An automated system for trace gas flux measurements from plant foliage and other plant compartments

Plant shoots can act as sources or sinks of trace gases including methane and nitrous oxide. Accurate measurements of these trace gas fluxes require enclosing of shoots in closed non-steady state chambers. Due to plant physiological activity, this type of enclosures, however, lead to CO₂ depletion in the enclosed air volume, condensation of transpired water, and warming of the enclosures exposed to sunlight, all of which may bias the flux measurements. Here, we present ShoTGa-FluMS, a novel measurement system designed for continuous and automated measurements of trace gas and volatile organic compound (VOC) fluxes from plant shoots. The system uses transparent shoot enclosures equipped with Peltier cooling elements and automatically replaces fixated CO₂ , and removes transpired water from the enclosure. The system is designed for measuring trace gas fluxes over extended periods, capturing diurnal and seasonal variations and linking trace gas exchange to plant physiological functioning and environmental drivers. Initial  measurements show daytime CH₄ emissions two pine shoots of 0.056 and 0.089 nmol g⁻¹ foliage d.w. h⁻¹ or 7.80 and 13.1 nmol m⁻² h⁻¹ . Simultaneously measured CO₂ uptake rates were 9.2 and 7.6 mmol m −2 h −1 and transpiration rates of 1.24 and 0.90 mol m⁻² h⁻¹ . Concurrent measurement of VOC emissions demonstrated that potential effects of spectral interferences on CH₄ flux measurements were at least ten-fold smaller than the measured CH₄ fluxes. Overall, this new system solves multiple technical problems that so far prevented automated plant shoot trace gas flux measurements, and holds the potential for providing important new insights into the role of plant foliage in the global CH₄ and N₂O cycles.