Effects of SO2 and/or NO2 on Native Plants of the Mojave Desert and Eastern Mojave-Colorado Desert

Ten species of plants, five perennials and five annuals, native to the Mojave desert were grown in pots and fumigated in open top plastic greenhouses, 25 hours/week, with SO2 and/or NO2. Three levels of SO2: 2.0, 0.67, and 0.22 parts per million (ppm); three levels of NO2: 1.0, 0.33, and 0.11 ppm; three treatments with 2.0 ppm SO2 + 1.0 ppm NO2, 0.67 ppm SO2 + 0.33 ppm NO2 and 0.22 ppm SO2 + 0.11 ppm NO2 plus untreated control plants were used in the fumigations. The perennials were fumigated for 16 weeks in 1977 and 32 weeks in 1978. Three species of annuals were grown and fumigated for 17 weeks, a fourth for 16 weeks, and a fifth for 12 weeks. A second crop of the first three annuals were grown; one for 12 weeks, a second for 8, and a third for 9 weeks. Individual species differed widely in their particular responses to the fumigants. The fumigations of perennials with 2.0 ppm of SO2 or NO2 at 1.0 ppm caused extensive leaf injury, and reduced growth or dry weight of Larrea divaricate Cav., Chilopsls lin...