Response of Chronically Ozonated Soybean Plants to an Acute Ozone Exposure

Abstract

The effects of chronic ozone (O/sub 3/) exposures on the sensitivity of soybean to a subsequent acute exposure to O/sub 3/ were measured. Plants were exposed to low concentrations (less than or equal to0.10 ppM O/sub 3/) or to charcoal-filtered air (0.0 ppM O/sub 3/) for 6 hr/day on 5, 10, or 15 consecutive days (chronic dose). One day after the last chronic exposure, plants were exposed for 3 hr to 0.20 ppM of O/sub 3/ (acute dose) or to filtered air. Plants exposed to chronic doses of O/sub 3/ below the visible injury threshold (less than or equal to0.06 ppM) were more sensitive to the acute O/sub 3/ dose than were plants exposed to filtered air. Plants exposed to chronic O/sub 3/ doses above the visible injury threshold (greater than or equal to0.06 ppM) were less susceptible to the acute O/sub 3/ dose than were plants exposed to filtered air. The predisposition toward greater sensitivity to the acute O/sub 3/ dose tended to be cumulative over time and was partially reversed by treatment with filtered air prior to the acute exposure. 10 references, 2 tables.