Interaction Between Ozone Exposure and Iron Nutrition in Two Tobacco Cultivars

The initial objective was to confirm evidence, obtained from field grown plants, for iron (Fe) accumulation in leaves under ozone exposure. Tobacco plants were grown in pots under either open air or growth chamber conditions. The ozone-sensitive cultivar Bel W3 showed symptoms of ozone injury only when grown outside, while the cultivar Virginia never developed symptoms. In both cultivars, basal leaves of plants grown outside had higher concentration of Fe, but not of manganese (Mn) or zinc (Zn), than those from the growth chamber. Results suggest an interference of the oxidative stress with the mechanisms regulating Fe homeostasis. A second objective was to test whether differences in tolerance to ozone correspond with differences in tolerance to Fe toxicity. Iron toxicity was induced by supplying an excess of Fe-EDTA to plants, grown hydroponically in a growth chamber, upon partial root cutting. Symptoms in leaves were more severe in Bel W3 than in Virginia, which suggested that mechanisms of tolerance to ozone were also effective against Fe toxicity. In both cultivars, a good correlation was determined between Fe accumulation and ethylene production in the leaves.