Effects of Ozone or Sulfur Dioxide on Pitch Pine Seedlings

Abstract

AbstractPitch pine seedlings (Pinus rigida Mill.) were fumigated with O3 or SO2 to determine their effects on growth and symptom expression. Seedlings fumigated twice with 0.20 µL O3 L−1 for 4 hr at age 14 and 22 wk had significantly greater shoot weight than those fumigated with 0.30 µL O3 L1; 0, 0.08, 0.10, and 0.15 µL L1 were intermediate and not significantly different. Root starch content tended to decrease with increasing O3 with control seedlings being significantly higher than the 0.15, 0.20, and 0.30 µL O3 L−1 treatments. Root starch of seedlings treated with 0.20, 0.50, 0.60, 0.70, and 0.90 µL SO2 L−1 was significantly lower than the controls. Seedlings from six families fumigated for 5 wk starting at age 6 wk differed in direction and degree of growth response when exposed to 0.08 and 0.30 µL O3 L1. Significant differences exited among families for needle weight, shoot weight, and total weight. No differences were found among O3 treatments within a family, but patterns suggest some pitch pine individuals may be sensitive to low O3 while others are stimulated. Visible injury consisted of light chlorotic mottle on oldest needles. Discriminant function analysis indicated that growth responses were indistinguishable among families receiving no treatment; however, treated seedlings could be classified based on various height measurements and/or shoot weight. Differences in visible injury were apparent among families of seedlings treated with 0.40 µL O3 L1, indicating some pitch pine families are more sensitive to O3 than others.