NITROGEN OXIDES PRODUCED DURING CO₂ ENRICHMENT: I. EFFECTS ON DIFFERENT GREENHOUSE PLANTS

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 (NO_x ). 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 NO_x . 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 NO_x was added. Furthermore, the time to flowering increased and number of flowers/flower buds decreased in Saintpaulia.