Short-term leaf responses of Nicotiana tabacum 'Bel-W3' to ozone under the environmental conditions of São Paulo, SE - Brazil

The present study aimed to study if the intensity and precocity of short-term leaf responses of Nicotiana tabacum 'Bel-W3' depended on the daily atmospheric levels of ozone and/or daily meteorological conditions in a State Park located in the city of São Paulo, SE Brazil. From 16 September to 14 October 2002, three lots of six potted plants were exposed for fourteen days. Leaf necrosis, atmospheric ozone concentrations and meteorological parameters were daily measured. The average percentage of leaf necrosis ranged from 5% to 20%. A 4th degree polynomial model was proposed to explain daily progress of leaf necrosis on plants. The average ozone levels were increased from morning (1.3-39.2 ppbv) to the midday (1.6-52.0 ppbv) and decreased in the evening (0.5-39.9 ppbv). Daily pattern of accumulated percentage of leaf necrosis was not strictly related to ozone, but was influenced by the meteorological conditions and stage of development of leaves. (AU)