Fig. 2.

Detection of NO₂-sensitive and -tolerant mutants. a. Approximately 3000 mutant plants per tray were grown for 2 weeks. Plants were fumigated for 1 h with 10 ppm NO₂ and 2 days later with 30 ppm NO₂. b Example of a sensitive mutant showing lesions after fumigation with 10 ppm NO₂ while neighbouring plants were unaffected. Pictures were taken at 48 h after fumigation. c Most plants were severely damaged after exposure to 30 ppm NO₂. d However, tolerant mutants exhibited only weak symptoms. Pictures were taken at 48 h – 96 h after fumigation. Note that the highlighted (red arrows) mutants exhibited altered NO₂-induced symptoms compared to all neighboring plants