Science Collected Works - Theses

Permanent URI for this collection

http://hdl.handle.net/11343/304

Filters

Reset filters

Settings
Statistics
Citations
Subject: Eucalyptus ×

Search Results

Now showing 1 - 4 of 4
  • Item
    No Preview Available
    [A study of the anatomy of Australian timbers in relation to their identification, classification and properties]
    Dadswell, H. E. (Herbert Eric), 1903-1964 (University of Melbourne, 1941)
  • Item
    Thumbnail Image
    A phylogenetic analysis of the bloodwood eucalypts (Myrtaeae)
    Osorio, Carlos Alberto Parra (University of Melbourne, 2009)
  • Item
    No Preview Available
    Molecular and physiological studies of salt tolerance in eucalypts
    Faridah, Eny (University of Melbourne, 2004)
    Effects of salinity on plant growth have been investigated in numerous studies looking at morphological, physiological and molecular aspects. In trees, and in eucalypts in particular, current knowledge is limited to the first two aspects. This stands in contrast to their important role in rehabilitation programs of salt-affected areas. This thesis made use of E. camaldulensis x E. globulus hybrid clones of known salt tolerance to investigate different molecular mechanisms utilized by these plants in response to salt stress. Effects of salinity on plant physiology and molecular biology were assessed after exposing clones to varying salt (NaCI) concentrations for different periods of time in a hydroponic experiment. EcgNaH, a gene fragment with homology to vacuolar Na+/H+ antiporter genes which, when overexpressed, is known to confer salt tolerance in many plant species, was identified and isolated from this hybrid. Also, fragments of genes known to be involved in nutrient uptake were identified and isolated, with particular focus on EcgPT, encoding a Phosphate Transporter. Expression studies using Northern-Blot analysis revealed that EcgNaH was upregulated in the presence of salt in an organ-specific manner, and increased over time when plants continued to be exposed to salt. EcgNaH was differently expressed in different clones, indicating, in combination with growth data, different levels of salt tolerance. Also the expression of EcgPT was found to be affected by salt suggesting a direct effect of salinity on phosphate uptake. EcgPT expression was regulated in an organ-specific way, and a time course analysis showed that EcgPT was increasingly upregulated after longer exposure to salt, but reaching a peak after three weeks of exposure indicating the plant's adaptation to the lower P status caused by salinity. EcgPT was expressed differently in different clones indicating different degrees of phosphate transporter activation in order to tolerate salt stress. Molecular data are discussed in relation to growth data and measurements of ion levels in different organs of different clones and under various salt regimes during the course of the hydroponic experiment.
  • Item
    Thumbnail Image
    Effect of carbon dioxide concentration on Eucalyptus ovata foliage and its utilisation by the common ringtail possum, (Pseudocheirus peregrinus)
    McDowell, Arlene. (University of Melbourne, 1998)
    Elevated C02 stimulates photosynthesis and alters the allocation of resources in leaves, which in turn influences plant-herbivore interactions. The alterations to leaf chemistry may render leaves less nutritious for herbivores. To test this hypothesis, Eucalyptus ovata trees were grown from seed for 1 year in glasshouses, where the concentration of C02 was ambient (~350 ?mol.mol-1) or elevated (~700 ?mol.mol-1), and their chemical compositions compared. As has been found previously with other eucalypts, E. ovata leaves from trees grown at elevated C02 contained 30% less nitrogen. Despite an increase in the concentration of total phenolics in leaves from plants grown at elevated C02 compared to ambient, an individual compound (i.e. macrocarpal G) that is important in mediating feeding by herbivores did not increase. Leaves also had a greater dry matter content, were thicker and less tough when grown at ambient compared to elevated C02. The chemical composition of leaves collected from the field also was investigated. All E. ovata saplings tested were non-cyanogenic. Foliage from the glasshouse was predicted to be palatable to ringtail possums by comparison with foliage of known palatability using principal component analysis of near infrared spectra. For the first time a mammalian herbivore, the common ringtail possum (Pseudocheirus peregrinus), was fed a diet of leaves grown at both ambient and elevated C02. There was no difference in intake of E. ovata foliage between the two C02 treatments, despite differences in foliage composition. Average values for foliage intake were 36.8 and 39.0 kg-0.75.d-1 for ambient and elevated C02, respectively. Thus unlike insects, marsupial folivores did not increase consumption to compensate for a diet that was lower in nutritional quality. There was a trend for measures of animal performance to be lower when fed leaves grown at elevated C02 compared to ambient; however, differences were not statistically significant. Gross energy intakes were similar between animals fed the foliage either from ambient or elevated C02, although digestible energy intakes (DEI) were lower at elevated C02. Average values for DEI were 276.5 and 257.0 kJ.g-1 for ambient and elevated C02, respectively. It is concluded that twice ambient C02 altered the chemical composition of E. ovata leaves although the common ringtail possums managed these changes, at least in the short term, due to metabolic and digestive adaptations to a diet of eucalypt leaves.