Title page for ETD etd-02262007-100007
|Type of Document
||Eaton, Gregory Kent
||Oxalic acid production by the ectomycorrhizal fungus Hebeloma westraliensis and its role in the nutrient acquisition and growth of Eucalyptus diversicolor in calcareous soil
||Master of Science
|Miller, Orson K. Jr.
|Nilsen, Erik T.
|Reneau, Raymond B. Jr.
|Scheckler, Stephen E.
- Hebeloma Growth.
- Karri Growth.
- Oxalic acid.
- Calcareous soils.
|Date of Defense
This work includes an introduction and literature review of mycorrhizal enhancement of
the mineral nutrition of host plants. Particular attention was paid to the role of
mycorrhizae in acquiring P from inorganic phosphates. Two experiments were designed
to study a mechanism by which the ectomycorrhizal fungus Hebeloma westraliensis can
enhance the availability and absorption ofP from Ca phosphate by Eucalyptus diversicolor
in calcareous soil. Chapter 2 reports on a study on the growth and oxalic acid production
of H. westraliensis in calcareous and noncalcareous liquid media. Oxalic acid is thought to
chelate cations from phosphate precipitates allowing the release of phosphate into
solution. L-threonine was added as an additional treatment to asses the ability of this
amino acid to inhibit oxalic acid production by the fungus. Growth and oxalic acid
production of H. westraliensis were increased in the calcareous systems. L-threonine had
little effect on dry weight of mycelium but substantially reduced oxalic acid production in the calcareous media. Chapter 3 reports on a study of E. diversicolor X H. westraliensis
mycorrhizal synthesis in model calcareous and noncalcareous systems. Oxalic acid
production was measured in these systems as well as various measurements of solution
and host plant nutrition. Solution P concentration decreased and solution Ca increased in
the calcareous systems. Mycorrhization decreased the solution concentrations of both of
these nutrient elements, due partly to sequestration of these elements in fungal and plant
tissues. Plant tissue P concentration was decreased and tissue Ca concentration increased
in the calcareous systems. Mycorrhization increased the concentrations of both of these
elements in plant tissues. Mycorrhization also increased the height and dry weight of
seedlings at harvest and ameliorated symptoms of nutrient deficiencies seen in
nonmycorrhizal plants in the calcareous system. Oxalic acid production by the fungus and
by the plant were increased in the calcareous system. Attempts to correlate oxalic acid
production with solution and plant nutrition were unsuccessful. The relationships of these
results to the mycorrhizal enhancement of plant nutrition in calcareous soil is discussed.
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