Thesis (M.S.)--Oregon State University, 1995. / Typescript (photocopy). Includes bibliographical references (leaves 66-74). Also available online.

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Please read the Summary in the section 00front of this document / Thesis (PhD)--University of Pretoria, 2005. / Genetics / Unrestricted

Two different types of rhizomorphs were produced by A. luteobubalina in vitro conditions - aerial and submerged. They differed in growth rate, amount of mucilage, extent of peripheral hyphae, degree of pigmentation and in the structure of inner cortex. Otherwise they had a similar internal structure comprising 4 radial zones, namely, peripheral hyphae, outer cortex, inner cortex and medulla. Two membrane permeant symplastic fluorescent tracers, carboxy-DFFDA and CMAC which ultimately sequestered in vacuoles, behaved in a similar fashion in aerial and submerged rhizomorphs regardless of whether pigment was present in the outer cortical cell walls or in the extracellular material. Rhizomorphs appeared to be mostly impermeable to these probes with exception of a few fluorescent patches that potentially connected peripheral hyphae to inner cortical cells. In contrast, the apoplastic tracer HPTS which was applied to fresh material and its localisation determined in semi-thin (dry) sections following anhydrous freeze substitution appeared to be impeded by the pigmentation in cell walls and/or the extracellular material in the outer cortical zone. Structures identified as air pores arose directly from the mycelium and grew upwards into the air. A cluster of rhizomorph apices is initiated immediately beneath the air pores. As air pores elongated they differentiated into a cylindrical structure. Mature air pores became pigmented as did also the surface mycelium of the colony. The pigmented surface layer extended into the base of air pores, where it was elevated into a mound by tissue inside the base of the air pore. Beneath the pigmented surface layer there was a region of loose hyphae with extensive gas space between them. This gas space extended into the base of the air pore and was continuous with the central gas canal of rhizomorphs. Oxygen is conducted through the air pores and their associated rhizomorph gas canals into the oxygen electrode chamber with a conductivity averaging 679??68x10-12 m3s-1. The time averaged oxygen concentration data from the oxygen electrode chamber were used to compare three different air pore diffusion models. It was found that the widely used pseudo-steady-state model overestimated the oxygen conductivity. Finally, a model developed on the basis of fundamental transport equations was used to calculate oxygen diffusivities. This model gave a better comparison with the experimental data.

The focus of this dissertation is on the design and micro-fabrication of an all silicon gas chromatography column with a novel two dimensional resistive heater and on its integration with an ultra-low power Thermal Conductivity Detector (TCD) for fast separation and detection of Volatile Organic Compounds (VOC). The major limitations of the current MEMS-GC column are: direct bonding of silicon to silicon, and peak band broadening due to slow temperature programming. As part of this thesis, a new gold eutectic-fusion bonding technique is developed to improve the sealing of the column. Separation of BETX, alkane mixture and VOCs were demonstrated with the MEMS GC column. The time and power required to ramp and sustain the column’s temperature are very high for the current GC columns. To reduce the time required to separate the compounds, a new temperature gradient programming heating method was developed to generate temperature gradients along the length of the column. This novel heating method refocuses eluding bands and counteracts some of the chromatographic band spreading due to diffusion resulting in an improved separation performance. A low power TCD was packaged and tested in a GC by comparison against FID for the detection of a mixture of VOCs. It demonstrated low power operation of a few milliwatts and a very fast response. The MEMS-GC was also demonstrated for rapid detection of the VOC gases released by pathogenic species of Armillaria fungus.

There are many health issues surrounding Alberta’s forests today and for the future. Health impacts of diseases, pests and climate change are currently being predicted in order to implement new management ideas and solutions, and identify specific research needs. This study examines state of the art knowledge on the current impacts of Armillaria root disease (ARD) (Armillaria spp.) in Alberta’s boreal forest region. It also assesses the biology and structure of the disease within this region to predict the extent to which the boreal forest may be impacted. In the next 50 years, both Armillaria ostoyae (Romag.) Herink and Armillaria sinapina Bérubé & Dessureault will become more of a problem, due to climate change and the current mature state of Alberta’s forests. A. sinapina, as a less-pathogenic but more opportunistic species, is predicted to be more prevalent that A. ostoyae, since the former will flourish when there are environmental stresses. Management practices will require research and evaluation of the use of alternative native tree species that have a higher resistance to the Armillaria species within Alberta and the impacts of such alternatives to the forestry industry and community structure. Future research is also essential to determine if one promising biological control agent and fungus, Hypholoma fasciculare (Huds. ex. Fr.), will be a viable and cost effective method to control Armillaria species within Alberta.

Two different types of rhizomorphs were produced by A. luteobubalina in vitro conditions - aerial and submerged. They differed in growth rate, amount of mucilage, extent of peripheral hyphae, degree of pigmentation and in the structure of inner cortex. Otherwise they had a similar internal structure comprising 4 radial zones, namely, peripheral hyphae, outer cortex, inner cortex and medulla. Two membrane permeant symplastic fluorescent tracers, carboxy-DFFDA and CMAC which ultimately sequestered in vacuoles, behaved in a similar fashion in aerial and submerged rhizomorphs regardless of whether pigment was present in the outer cortical cell walls or in the extracellular material. Rhizomorphs appeared to be mostly impermeable to these probes with exception of a few fluorescent patches that potentially connected peripheral hyphae to inner cortical cells. In contrast, the apoplastic tracer HPTS which was applied to fresh material and its localisation determined in semi-thin (dry) sections following anhydrous freeze substitution appeared to be impeded by the pigmentation in cell walls and/or the extracellular material in the outer cortical zone. Structures identified as air pores arose directly from the mycelium and grew upwards into the air. A cluster of rhizomorph apices is initiated immediately beneath the air pores. As air pores elongated they differentiated into a cylindrical structure. Mature air pores became pigmented as did also the surface mycelium of the colony. The pigmented surface layer extended into the base of air pores, where it was elevated into a mound by tissue inside the base of the air pore. Beneath the pigmented surface layer there was a region of loose hyphae with extensive gas space between them. This gas space extended into the base of the air pore and was continuous with the central gas canal of rhizomorphs. Oxygen is conducted through the air pores and their associated rhizomorph gas canals into the oxygen electrode chamber with a conductivity averaging 679??68x10-12 m3s-1. The time averaged oxygen concentration data from the oxygen electrode chamber were used to compare three different air pore diffusion models. It was found that the widely used pseudo-steady-state model overestimated the oxygen conductivity. Finally, a model developed on the basis of fundamental transport equations was used to calculate oxygen diffusivities. This model gave a better comparison with the experimental data.

Thesis (Ph. D.)--Oregon State University, 1994. / Typescript (photocopy). Includes bibliographical references (leaves 126-143). Also available on the World Wide Web.

DNA-DNA hybridization experiments were used to examine the genetic variation that has accumulated with the North American Biological Species (NABS) of Armillaria. Forty strains including nine of the ten NABS and A. tabescens were used in this study. The normalized percent hybridization values ranged from 80%-100% similarity within a given biological species and ranged from 30%-85% among the biological species, The NPH data was summarized with UPGMA clustering analysis to give four main clustering groups, two were homogeneous and two were heterogeneous, The first included A. tabescens; the second included A. mellea; the third included A. calvescens, A. gallica, A. sinapina, NABS IX, and NABS X; the fourth included A. gemina and A. ostoyae. One cluster of two A. gallica strains shared greater similarity with NABS X than it had to four other conspecific strains, The NPH data and estimates of genome size (genetic complexity) was analyzed using a stoichiometric approach to calculate equivalents of homologous DNA and low copy repetition frequencies. Reciprocal NPH values did not predict relative genome size as expected, However, as the relative genome size increases, the equivalents of homologous DNA increases in the same proportion. This suggests that as an Armillaria genome increases in total complexity (novel sequences), certain ancestral sequences are duplicated in proportion the increase in total genetic complexity, This interpretation of the data is discussed with respect to interspecific hybridization, diploidy, and chromosomal evolution including alloploidy, aneuploidy, and chromosomal length polymorphisms. / Ph. D.

Thesis (M.S.)--Oregon State University, 2004. / Printout. Includes bibliographical references (leaves 148-159). Also available online.