VIEW ARTICLE

Etiology

Ozone and Sulfur Dioxide Mixtures Cause a PAN-Type Injury to Petunia. Elizabeth Lewis, Graduate Student, Department of Plant Pathology, Cook College, Rutgers University, New Brunswick, NJ 08903; Eileen Brennan, professor, Department of Plant Pathology, Cook College, Rutgers University, New Brunswick, NJ 08903. Phytopathology 68:1011-1014. Accepted for publication 20 January 1978. Copyright © 1978 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-68-1011.

Foliage of petunia plants exposed to a mixture of ozone (O₃) and sulfur dioxide (SO₂) in a controlled environment developed a symptom that fits the description of classic peroxyacetylnitrate (PAN) injury. The undersurface of newly matured leaves became glazed, especially at the apex of the youngest susceptible leaf, at the middle of the intermediate-aged leaf and at the base of the oldest susceptible leaf. As with PAN, injury was more severe on a white-flowered cultivar than on a red-flowered one. In contrast to the result reported for PAN-fumigated plants, prior treatment with benomyl afforded some protection against injury from the mixture of O₃ and SO₂ in controlled fumigations. In a field study conducted in New Jersey in the summer of 1975, white petunia cultivars responded to ambient air pollution in a manner identical to that observed in controlled fumigations with the mixture of O₃ and SO₂. We question the generally accepted notion that petunia damage in the northeastern USA is a consequence to toxic levels of PAN and we suggest an alternative cause, a mixture of O₃ and SO₂.