CHEMICAL REGULATION OF OZONE SUSCEPTIBILITY IN NICOTIANA TABACUM

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Abstract
Detached leaves of Nicotiana tabacum L. (var. White Gold), treated with urea, potassium nitrate, kinetin, or p-hydroxybenzoic acid became more susceptible to ozone injury. The chemically induced susceptibility was reversed by a subsequent treatment with sucrose and, to a less extent, with 3,4-dihydroxybenzoic acid or L-cysteine. The degree of reversibility was proportional to the duration and concentration of the respective treatment. The chemical modification of ozone susceptibility was effective on leaves at different stages of maturity. In the urea-treated leaves, the level of cytoplasmic non-protein nitrogen was positively correlated with the severity of ozone injury (r = 0.617). Positive correlations between leaf sensitivity and both total soluble nitrogen and ammonia nitrogen were also significant. A sucrose treatment after urea treatment effectively reduced the soluble-nitrogen fractions.
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