Young Scotch pine seedlings in the cotyledon, primary, and secondary needle stages were exposed to 2620 μg/m3 (1.0 ppm) SO2 for 1, 3, or 5 hours. Exposures were conducted at time of needle emergence, and when the current foliage was 1, 3, 5, and 7 weeks of age. Secondary needles were generally more sensitive than were primary needles. Cotyledons were generally more tolerant than the other two needle types. The sensitivity of all three needle types was at a minimum at time of needle emergence, increased through 3 to 5 weeks, and then remained constant or decreased from 5 to 7 weeks. All three needle types exhibited needle tip necrosis as the common symptom.
|Original language||English (US)|
|Number of pages||5|
|Journal||PLANT DIS. REP.|
|State||Published - Jan 1 1977|
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