Absorption of nitrogen dioxide by barley in open-top chambers

Foliar absorption of nitrogen dioxide in barley (Hordeum vulgare L.) exposed to mean NO₂ concentrations of 4 and 37 ppb was studied in open-top chambers. The possible compensation for insufficient supply of nitrogen in the growth medium by increased uptake of NO₂ from the air was investigated by growing plants with sub-optimal and optimal N supply. The amount of NO, derived from fumigation was estimated using the ¹⁵N dilution technique, in which the nitrogen derived from the growth medium was labelled with ¹⁵N. The absorption of NO₂-N from polluted air contributed 5–6% of the total N. An additional 3–5% was derived from other N sources, probably also of gaseous origin. Thus, total absorption from gaseous sources in the NO2-fumigated plants was estimated to be approximately 10% of total N. The amount absorbed from aerial sources was proportional to the top weight. The amount of NO2 absorbed was highest in the plants with optimal N supply. However, in plants grown with sub-optimal N, there was a relatively higher contribution to total N from the NO₂-N.