Effects of Sulfur Dioxide on Pinus resinosa Seedlings in the Cotyledon Stage

Abstract

AbstractSeedlings of red pine (Pinus resinosa Ait.) in the cotyledon stage of development were exposed to four concentrations of SO2 (0.5, 1, 3, or 4 ppm) at four exposure times (15, 30, 60, or 120 minutes). Seedling development was inhibited by SO2 at all concentrations for 120 minutes and at 1.0 ppm and above for 30 minutes or longer. The adverse effects were proportional to SO2 concentration and duration of exposure. The fumigations induced chlorosis in both cotyledons and primary needles, slowed expansion of primary needles, inhibited dry weight increment of both cotyledons and primary needles, and induced necrosis of tips of cotyledons and primary needles. Growth of seedlings was inhibited more by increasing the duration of exposure to SO2 than by increasing SO2 concentration. The extreme sensitivity to SO2 of pine seedlings in the cotyledon stage suggests that their exposure to continuous fumigation in the field, even at low dosages, may adversely influence seedling development and regeneration of pine communities.