Absorption of atmospheric NO2 by several herbaceous species: estimation by the 15N dilution method

Abstract

SUMMARYAbsorption of nitrogen dioxide (NO2,) by eight herbaceous species was determined by the 15N dilution method. The plants were continuously exposed to NO2, at 0.5 μll−1 for 2 weeks. Susceptibility to NO2, was simultaneously examined in the tested species to see if this was correlated with the rate of absorption.The total amount of NO2‐nitrogen absorbed by a plant during the 2‐week exposure period primarily depended on the size of the plant. Among the tested species, sunflower showed the highest rate of NO2, absorption per unit leaf area, reaching as much as 0.55 mg N dm −2 d−1, which was about four times greater than that for sorghum which had the lowest rate. A highly significant correlation was observed between the rate of absorption and the stomatal conductance among the species. A proportion of the NO2‐nitrogen accumulated in the plant might be absorbed via the air‐soil‐root route.Sunflower and radish which had higher rates of NO2 absorption than the other species were more susceptible to NO2. On the contrary, sorghum and maize which showed a lower rate of NO2, absorption were tolerant. Consequently, the higher susceptibility to NO2 of radish and sunflower is considered to be directly related to their superior ability to absorb NO2.