Grasslands cover vast terrestrial areas and the main biomass is concentrated in the lowest part of the canopy. We found that measured transport times in the lowermost canopy layer are fastest during nighttime. During daytime, the reaction of NO with O3, as well as NO2 uptake by plants, was faster than transport. This suggests that grassland canopies of similar structure may exhibit a strong potential to retain soil emitted NO due to oxidation and subsequent uptake of NO2 by plants.