Response of abscisic acid in soybean leaves to NO2 exposure

Soybean (Glycine max L. Merril) cv. 'Williams' plants were exposed 0.0, 0.05, 0.2 and 0.4 microl litre(-1) NO(2) under controlled environment. Amount of abscisic acid (ABA) was measured after either 7 h or 5 days of exposure as well as after 18 h of recovery period. For quantitative analysis of ABA enzyme-linked immunosorbent assay was used. A significant increase (160%) was observed in plants treated with 0.4 microl litre(-1) NO(2) for 5 days compared to an increase of only 82% on exposure for 7 h. Rate of recovery for plants treated with low doses of NO(2) was higher than those treated with higher doses.