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Combined Effects of Peroxyacetyl Nitrate and Ozone on Growth of Four Tomato Cultivars¹

ABSTRACT

In a greenhouse exposure chamber study to determine the combined effects of peroxyacetyl nitrate (PAN) and ozone (O₃) on foliar injury and growth of four cultivars of tomato (Lycopersicon spp.), 4-week-old plants were exposed to 0, 125, and 250 µg m^–3 PAN and 0, 200, and 400 µg m^–3 O₃, and all combinations, 4 h/d, once per week for 3 weeks. Plants were harvested 1 week after the last exposure. The experiment was repeated twice. Ozone induced trace (ca. 1%) foliar injury at 200 µg m^–3 and moderate (30–50%) foliar injury at 400 µg m^–3. Peroxyacetyl nitrate caused no foliar injury development, either alone or in combination with O₃, and had no effect on O₃ injury. Foliar injury on the four cultivars increased in the order ‘Heinz 1350,’ ‘Tiny Tim,’ ‘Ace,’ and ‘Pyxie.’ Ozone by itself produced a significant linear reduction in growth of the four cultivars. Plants exposed to PAN alone also showed reduced growth but results were not statistically significant at the 0.05 level. Combinations of O₃ and PAN had less than additive effects on growth reduction, but greater than additive effects on shoot/root ratios. This difference was attributed to greater suppression of root growth relative to leaf growth induced by O₃-PAN mixtures.

Key Words: air pollutant interactions • Lycopersicon spp. • oxidants • shoot-root ratios • ozone • peroxyacetyl nitrate

¹ Contribution of the Statewide Air Pollution Research Center and Dep. of Botany & Plant Sciences, Univ. of California, Riverside, CA 92521.

² Assistant research botanist, Statewide Air Pollution Research Center and professor, Dep. of Botany & Plant Sciences, Univ. of California, Riverside, CA 92521.

Received for publication March 2, 1983.