Graduate Thesis Or Dissertation
 

Effects of the balsam woolly aphid (Adelges piceae (Ratzburg)) on the cambial activity of grand fir (Abies grandis (Dougl.) Lindl.) and subalpine fir (Abies lasiocarpa (Hook.) Nutt.)

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  • Cambial activity was studied in trees infested by the balsam woolly aphid and in non-infested trees of grand and subalpine fir. Infested and non-infested samples of grand fir were collected near Corvallis during 1968 and 1969. Samples of subalpine fir, noninfested and infested, were collected near Odell Lake, at approximately 5, 000 ft. elevation, during 1969. Light infestations of the aphid were observed in both species. No differences within species between infested and non-infested trees were noted in the number of overwintering immature (precocious) sieve cells or in the dates for reactivation and cessation of mitotic activity in the cambial zone, or in the number of cambial zone cells per radial file. The relative amounts of xylem and phloem present at any given time during the growing season were the same regardless of the presence or absence of aphids. Significant differences were noted in the lengths of the fusiform initials in the infested samples when compared to non-infested samples in both species. Xylem production in grand fir, and phloem production in both species was significantly greater in infested samples. A greater number of phloem parenchyma strands were observed in infested samples of grand fir than in non-infested samples. The rate of cell division, as indicated by the mitotic indices, showed no significant differences between samples of infested and non-infested trees of either species. Differences in xylem and phloem production between infested and non-infested trees could not be attributed to either an increased rate of cell division or an increase in the number of cambial zone cells per radial file in infested samples for either species.
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Déclaration de droits
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