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Responses of Radish to All Combinations of Three Concentrations of Nitrogen Dioxide, Sulfur Dioxide, and Ozone1

  1. R. A. Reinert,
  2. D. S. Shriner and
  3. J. O. Rawlings2



Vegetation stress by air pollutants is frequently a result of a multiple pollutant exposure. Long-range transport of major air pollutants may affect rural agricultural and forested regions of the eastern United States. Also, changes in the relative importance of the major phytotoxic pollutants, NO2, SO2, and O3, can be anticipated as a result of changing energy patterns. In experiments designed to evaluate the effects of the coincident occurrence of NO2, SO2, and O3, as well as the importance of the ratios of the pollutants to one another, we have demonstrated that the pollutants interacted to influence the response of radish (Raphanus sativus L.) foliage and root.

The influence of increasing O3 concentrations at increasing concentrations of NO2 and SO2 generally resulted in smaller root (hypocotyl) fresh and dry weight, and in most cases the relationship was linear. Fresh-weight reductions in radish roots due to increasing O3 concentrations from 0.1 to 0.2 ppm and from 0.1 to 0.4 ppm at 0.1 ppm NO2 and SO2 were 24 and 51%, respectively. At 0.4 ppm NO2 and SO2, the root-weight losses due to increasing O3 concentration from 0.1 to 0.2 and from 0.1 to 0.4 ppm were 20 and 38%, respectively. When SO2 reached 0.8 and 1.6 ppm, there was little change in root weight as NO2 and O3 concentrations were increased from 0.2 to 0.4 ppm. Nitrogen dioxide played a significant role in the response of radish to SO2 and O3, considering the high concentration of NO2 (> 2.0 ppm) needed to cause a response in radish from a single exposure to NO2 alone. These results suggested that valid assessment of the impact of siting additional sources of SO2 and NO2 in regions currently experiencing elevated O3 levels will require recognition of this interaction potential.

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