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 NO2 derived from fumigation was estimated using the N-15 dilution technique, in which the nitrogen derived from the growth medium was labelled with N-15. 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.