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Variable Effects of Ozone on Pinto Bean Internodes. Ida A. Leone, Associate Research Professor, Department of Plant Biology, Cook College, Rutgers University – The State University of New Jersey, New Brunswick 08903; Eileen Brennan, Associate Research Professor, Department of Plant Biology, Cook College, Rutgers University – The State University of New Jersey, New Brunswick 08903. Phytopathology 65:666-669. Accepted for publication 11 January 1975. DOI: 10.1094/Phyto-65-666.

Ten- to 14-day-old Pinto bean seedlings exposed to ozone exhibited positive, negative, or no effects on internodal elongation according to ozone dosage. At the foliage-marking dosage of 600 µg/m³ (0.30 ppm) ozone for 3 hours there was an inhibition; whereas, at sublethal dosages of 200 µg/m³ (0.10 ppm) for 48 or 72 hours, there was a stimulation of growth in internodes which were starting to elongate during the ozone exposures. Intermediate dosages had no effect. The initiation of new internodes also appeared to be stimulated by the lower-level ozone exposures.