Plant-mediated -transport (PMT) and -exchange (PME) of greenhouse gases (GHGs) are increasingly recognised as important and may dominant pathways for soil-produced GHGs to reach the atmosphere in certain ecosystems. However, methods to directly quantify PMT/PME remain limited. Chamber-based approaches using closed-transient methods have been applied at the canopy and whole-plant scale, but physiological response by the plant under ever changing chamber conditions and challenges extracting physiological parameters from closed-transient measurements have limited the utility of such approaches. Plant physiological responses are typically measured in open flow-through systems to minimise perturbation of physiology. Portable photosynthesis systems measure CO2 and H2O concentrations before and after interacting with the leaf. The differences between which permit calculation of physiological parameters including net CO2 assimilation (A), intercellular CO2 concentration (Ci), and stomatal conductance (gsw) while the chamber is continuously refreshed with stable air, allowing the maintenance of the leaf at a physiological steady-state. However, for leaf-level measurements open flow-through approaches have seen little application for quantifying PMT/PME. Here we describe and characterise a system that integrates commercial OF-CEAS trace gas analysers, for measuring CH4 and N2O (LI-COR LI-7810 and LI-7820 respectively) with a commercial photosynthesis system (LI-COR LI-6800). We examine the impact of averaging interval on measurement precision for a range of CO2 mole fractions and assess the dependence of trace gas mole fraction to changing CO2 mole fractions. We also present a sensitivity analysis for zero trace gas flux.