The response of radish to nitrogen dioxide, sulfur dioxide, and ozone , alone and in combination

Effects on radish (Raphanus sativus L.) cv. Cherry Belle of nitrogen dioxide (NO/sub 2/), sulfur dioxide (SO/sub 2/), and ozone (O/sub 3/) alone and in combination at 0.2 and 0.4 ppM of each pollutant were studied. There was no difference in foilage or root weight of radish between exposure durations of 3 to 6 hours, and no significant interaction of hours with air pollutant and concentration. Ozone reduced root dry weight more at 0.4 ppM than at 0.2 ppM. Sulfur dioxide depressed the root/shoot ratio at both 0.2 and 0.4 ppM; however, when NO/sub 2/ and SO/sub 2/ were both present there was synergistic depression of the root/shoot ratio at 0.4 ppM. The average O/sub 3/-induced reduction in root weight of radish (1.75 g fresh and 101 mg dry, per plant) was additive in the presence of NO/sub 2/ and SO/sub 2/. The weight of the root was reduced even though the foilage was the direct receptor of the pollutant stress.