Browsing by Subject "Soil fungi"
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Item Composition and biosynthesis of sterols by Mortierella alpina(Texas Tech University, 1998-08) Nichols, Shawnn DerrekSterols from mycelia of Mortierella alpina CBS 210.32. a zygomycetous fungus, were identified by thin layer chromatography, gas-liquid chromatography, reversed phase-high performance liquid chromatography, gas chromatography/mass spectrometry. And whenever possible proton nuclear magnetic resonance spectroscopy The nonsaponifiable lipid fraction accounted for 1% of mycelial dry weight, and the total sterol content accounted for 0.07% of the mycelial dry wt. Desmosterol was the principal sterol of the mycelia. Previously reported sterols from this fungus have been isolated from the mycelium and their identities confirmed by chromatographic and spectral methods. Several new sterols were isolated from the fungus and identified in stereochemical detail here for the first time. Selected incubations with [^H3-methyl] methionine have aided in the elucidation of M alpifia's biosynthetic sterol pathway, as well as further confirming minor components present in the mycelia. The results are interpreted to imply that flingal phylogenetic linkages exist in relation to sterol synthesis.Item Fungal community structure and microbial biomass in a semi-arid environment: roles in root decomposition, root growth, and soil nitrogen dynamics(Texas Tech University, 1996-05) Zhang, QishuiAlthough the roles of fiingi in ecosystems are recognized, few studies have examined the enzymatic activities of fungi during plant litter decomposition and the changes in species composition of microbial communities as they influence soil nutrient levels, root growth, and plant litter decomposition in a semi-arid or arid environment. To examine aspects of the potential linkages among plant growth, soil levels, and microbial activities in a semi-arid environment, five 40-m transects were established in a sand shinnery-oak (Ouercus havardii Rydb.) ecosystem in West Texas in 1993. Along these transects, species conqx)sition of fungal communities and community-level enzymatic activities were evaluated during decomposition of fine roots of sand shinnery-oak. Soil microbial biomass and nitrogen transfonnation processes were evaluated along the transects to establish the linkages between plant density, microbially mediated processes, and nutrient availability. Temporal pattems of ectomycorrhizal colonization levels and fine root production also were estimated to integrate microbial enzymatic activities, nutrient fluxes, and root growth. In response to results obtained during the fall of 1993 and spring of 1994, a nitrogen addition experiment was established to examine the effects of nitrogen on amount of soil microbial biomasscarbon, net nitrogen mineralization rates, fine root production and ectomycorrhizal colonization levels. To better understand the strengths of the interrelationships among root growth, nutrient fluxes and microbial enzymatic activities, conceptual models exploring the relationships were developed and evaluated using path analysis.Item Fungal functional diversity: exploring patterns and processes associated with soil fungal assemblages along an altitudinal gradient in the Chihuahuan Desert(Texas Tech University, 2002-05) Sobek, Edward AndrewSoil fungi are intimately associated with the maintenance and stability of terrestrial ecosystems through their involvement in the decomposition process. During decomposition, organic carbon is mineralized to CO2 and bound nutrients are returned to the labile soil nutrient pool for subsequent growth of plants and soil microbes. To better understand the relationship between soil fungal diversity, and factors influencing their functional ability in the decomposition of soil organic matter, this dissertation examined, (1) development of methods to determine soil fungal functional diversity, (2) seasonal trends in fungal function al diversity, and (3) the relation between soil fungal functional abilities and a suite of environmental variables that are important in ecosystem nutrient cycles. The context of this research endeavor focused on assemblages of soil fungi associated with an environmental gradient in the Chihuahuan Desert, specifically, the Pine Canyon Watershed in Big Bend National Park. The Pine Canyon Watershed contains five distinct vegetation zones along an altitudinal gradient and contains the majority of vegetation types that are found in the Chihuahuan Desert. Soil samples were collected within each of these zones over a three-year period. Sampling coincided with seasonal changes in temperature and precipitation. Functional diversity was determined for fungal assemblages from each vegetation zone, using the Soil FungiLog procedure developed from this research.Item The effects of even-chain-length fatty alcohols on growth and respiration of Fusarium oxysporum(Texas Tech University, 1973-05) Humphrey, Robert T.Not available