Plants were grown in chambers with CO2 enrichment (1000 μl 1−1) and with or without the addition of 0.85 μl 1−1 nitrogen oxides (NOx).
The following species were tested: Lactuca sativa (lettuce), Cucumis sativus (cucumber), Lycopersicon esculentum (tomato), Saintpaulia ionantha, Rosa, Kalanchoe blossfeldiana, Chrysanthemum×morifolium, Helxine soleirolii, Hedera helix, and Nephrolepis exaltata. All species responded positively to an increase in CO2 level from 330 to 1000 μl 1−1. The dry weights of tomato, roses and Saintpaulia responded negatively to the addition of NOx. In tomato, the reduced dry weight was due to reduction in shoot length and leaf area. In roses the stem was shorter and in Saintpaulia the leaves smaller when NOx was added. Furthermore, the time to flowering increased and number of flowers/flower buds decreased in Saintpaulia.