Response of Plants to Air Pollutants. III. A Relation between Ascorbic Acid Levels and Ozone Susceptibility of Light-Preconditioned Tobacco Plants

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Abstract
Light preconditioning caused increased concentrations of ascorbic acid in the leaves of 2 tobacco vaeieties. The increases occurred in leaves representing rapid leaf expansion, maturity, and recent maturity. Ozone fumigations of light-precondtioned plants showed that ozone injury to leaves declined as ascorbate levels increased. Ascorbate concentrations in light-preconditioned leaves were 2.5-3.3 times as much as controls. Ozone damage from 2-hour exposures at 0.28 ppm was recuded to about 50% of control plants. Preferential oxidation of ascorbic acid was regarded as the probable cause of the partial ozone protection induced by light preconditioning. Results of this work, however, do not show an obvious or direct relation of ascorbic acid metabolism to fundamental differences in varietal resistance or susceptibility to ozone.