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Thesis (Ph. D.)--University of Adelaide, Dept. of Botany, 1985. / Includes bibliographical references (leaves [347]-361).

Thesis (B.A.(Hons.)) -- University of Adelaide, 1977. / Includes bibliographical references (p. 31-32).

Four species of Phoradendron were examined for seedling morphology: P. bolleanum subsp. densum (on Juniperus), P. californicum (on Prosopis), P. juniperinum subsp. juniperinum (on Juniperus, P. villosum subsp. villosum (on Quercus). The main species used in the study was P. juniperinum, using the other species for comparison. The initial shoot(s) of P. juniperinum may develop from the epicotyl of the developing seedling, from adventitious buds which arise from a cushion of tissue, termed the haustorial cushion, formed beneath the holdfast, or from both positions. When shoots arise only from adventitious buds the original seedling remains attached in a lateral position, often persisting for a number of years, giving the false impression of an autoparasite establishing itself near the base of the plant. In P. bolleanum and P. villosum, initial shoots arise from the epicotyl although adventitious shoots may also develop, particularly in P. bolleanum. In contrast, P. californicum shoots are entirely adventitious in origin, and the initial seedling can frequently be seen near the center of the cluster of adventitious shoots. Cotyledons of all species in the study were found to be persistent and possess a distinctive tip probably resulting from the site of attachment to the endosperm. These distinctive, persistent cotyledons and other clearly identified morphological features, allow to readily distinguish between plumular and adventitious shoots.

The aerial shoot pigments of three epiphytic mistletoes and their hosts were examined and the results were found to concur with earlier reports. Emphasis was placed on the mistletoe Phoradendron juniperinum. Absorbance spectroscopy indicated a very similar ratio of pigments in both the aerial tissue of the mistletoe and its juniper host. Spectroscopic examination found the presence of chlorophyll in the endophytic tissue of the genus Phoradendron for the first time. Total chlorophyll concentrations of the endophytic tissue of Phoradendronjuniperinum were found to be approximately 10% that of aerial shoots. However, chlorophyll alb ratios of endophytic tissue were 40% of those in aerial tissue. The dwarf mistletoe Arceuthobium tsugense was found to have about 1/3 the chi content of its host and of the two Phoradendron species examined. However, the endophytic concentrations of chlorophyll of A. tsugense were 250% higher than those found in compatible Phoradendron tissue. Ultrastructural inspection of Phoradendron juniperinum revealed chloroplasts of the aerial shoots to be typical of C3 plants, yet they were small and contained little relative stroma lamella. This is characteristic of plants with unequal complement of the two photosystems. Examination of the endophytic system indicated that the most likely source of the chlorophyll to be plastids with enlarged thylakoid channels. These plastids were termed endophytic-chloroplasts Experiments were performed to establish whether the synthesis of the chlorophyll within the endophytic system was via a light-independent pathway or by means of light penetration into mistletoe tissue and stimulation of the typical angiosperm light-dependent pathway. However, results as to the biosynthesis of chlorophyll were inconclusive. These experiments did indicate that chlorophyll was still present in endophytic tissue of Phoradendron juniperinwn after 11 months without aerial shoots, whether enclosed in complete darkness or not. Microscopic examination of tissue did not revile the presence of any light conductive tissues in either the parasite or its host.

Thesis (Ph. D.)--Oregon State University, 1981. / Typescript (photocopy). Includes bibliographical references (leaves 49-53). Also available on the World Wide Web.

The increase of discrete populations of dwarf mistletoe (Arceuthobium americanum Nutt.) plants or infections was studied in 20 year old stands of lodgepole pine (Pinus contorta Dougl.). Mistletoe infections were selected from infected trees in three areas 100 to 200 ft. in diameter. The age of each infection was determined by dissecting the infected host wood. It was found that the number of infections established annually had increased logarithmically during the preceding 8 to 10 years. Therefore the logarithmic rates of increase in the number of infections could be calculated to describe the past epidemic growth of each mistletoe population. The logarithmic rates (equivalent to "compound" increase of 66 to 96 per cent per year) demonstrated rapid population increase. Although the three mistletoe populations had developed in apparently different environments, the population rates of increase were not statistically different. However, for the study of ecological aspects of dwarf mistletoe epidemics this approach appears quite promising. / Forestry, Faculty of / Graduate

The vertical rate of spread of dwarf mistletoe was studied in two actively growing, young hemlock stands. This was done by determining the height and age of successive oldest and highest female infections. The rate of spread was calculated by dividing the sum of the heights of advances by the total number of years lapse between successive advances. The mean vertical spread rate was 2.1 ± 0.1 ft./yr. in a relatively open stand and 1.0 ± 0.1 ft./yr. in a relatively dense stand. The mean rate of tree growth during the maximum growth phase in the open stand was 2.5 ft./yr. and for the dense stand 1.5 ft./yr. However, over the past 25 years, the growth rate of the trees in the open stand was 1.9 ft./yr. and for the dense stand 1.1 ft./yr. The number of new infections per year increased geometrically, doubling every four years in both the dense and open stands. However, the geometric increase levelled off six years ago in the open stand and five years ago in the dense stand. During the maximum growth phase of hemlock in an open and dense stand, the most photosynthetically active upper portion of the crown remains free of mistletoe infection. Until the senescent phase is reached, the trees can be expected to outgrow the mistletoe and intensification will be restricted to the lower portions of the crowns. It is tentatively concluded that provided there is no overstory seed source and no disruption of the natural stand, such as thinning, dwarf mistletoe on hemlock will not become serious until the rate of height growth of the trees falls below the rate of vertical spread, i.e., not until after the presently accepted rotation age. / Forestry, Faculty of / Graduate

The number, height and age of western hemlock dwarf mistletoe (Arceuthobium tsugense (Rosendahl) G.N. Jones) infections were recorded in two western hemlock (Tsuga heterophylla (Raf.) Sarg.) stands (44 and 130 years old) located on similar sites on the University of British Columbia Research Forest at Maple Ridge, B.C.. The rapid decrease in numbers of infections with infection age was shown to be largely due to infection mortality. The rate of intensification of the disease expressed as "doubling time" was estimated to be 40 or more years in both stands. Also estimated was a rate of vertical spread of .15 metres per year. The results differed markedly from those of other studies in similar stands, which generally predict "doubling times" of 2 to 4 years and vertical spread rates of up to .5 metres per year. / Forestry, Faculty of / Graduate

Thesis (M.S.)--Oregon State University, 1996. / Includes color map in pocket. Typescript (photocopy). Includes bibliographical references (leaves 96-103). Also available on the World Wide Web.