Wetlands and other ecosystems at terrestrial-aquatic boundaries play an important role in controlling the release of reactive nitrogen from nonpoint sources into sensitive aquatic environments via microbial denitrification. Denitrification can lead to the accumulation and emission of nitrous oxide (N2O), an important greenhouse gas (GHG) and ozone-depleting substance. Minimizing the potential tradeoff between water quality protection and GHG emissions, particularly in the context of constructed wetlands, requires process-level understanding of N2O production, consumption, and the gas transfer processes mediating N2O transfer from wetland soils to the atmosphere. The objective of this research was to explore N2O transport through the root aerenchyma system of wetland macrophytes as a pathway for N2O emissions from wetland soils. While plant-mediated transport is well-recognized as a critical emission pathway for methane, there has been little attention to the role of this process in N2O fluxes from wetlands. This study addresses two questions:1) What are the kinetic constants for root-mediated N2O transport and reaction rate constants for N2O microbial reduction in the wetland rhizosphere; and 2) How significant is the root uptake pathway compared to the microbial reduction pathway of N2O under environmentally relevant N2O concentrations? A set of laboratory vertical flow constructed wetland mesocosms were used to evaluate the role of wetland macrophytes on N2O dynamics in denitrifying wetland buffer systems. Dissolved gas tracer push-pull tests (PPTs) [1][2] were used to probe the in situ behavior of N2O in the wetland rhizosphere and determine the relative contribution of microbial N2O reduction vs. N2O transfer into roots in controlling the fate of N2O produced in vegetated wetland soils. Two different modeling approaches were employed to interpret the experimental data and estimate kinetic constants for N2O gas transfer based on the inert gas tracers helium and sulfur hexafluoride. The accuracy of these approaches was evaluated using a holdout cross-validation approach. Results showed that plant uptake only accounts for 0.49% to 17.16% of total N2O removed from the subsurface of the experimental mesocosms, indicating the root uptake pathway represents a relatively small N2O sink. The relative importance of the root N2O sink depends on the rates of microbial N2O reduction, which can vary widely. Thus, N2O emission via plant-mediated pathways is likely to represent a small fraction of the wetland N2O budget, particularly in settings where microbial N2O reduction is fast.