School of Botany - Theses
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ItemA molecular and taxonomic appraisal of selected tribes and genera of the Rhodomelaceae (Ceramiales: Rhodophyta)( 2001-07)The largest of the 80 families in the division Rhodophyta is the Rhodomelaceae. A great many genera and species are restricted to Australasia, which is the major centre of diversity and distribution. Perhaps as a consequence, the Rhodomelaceae has remained relatively unstudied compared with most other red algal families even at the morphological/anatomical level. Within the confines of a PhD program it would not be possible to study all of the 125 genera credited to the Rhodomelaceae. The focus of this thesis has, therefore, been narrowed down to selected tribes and genera, all of which have a strong Australasian component. Anatomical and molecular analyses have been undertaken on members of the tribes Amansieae, Pleurostichidieae, Streblocladieae and Sonderelleae and the genus Halydictyon. The results of these analyses have led to the description of two new genera, three new species, and one new tribe as well as the resurrection of two genera and the recombination of ten species. The taxonomic position and validity of the studies tribes and genera has also been established.
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ItemA cladistic and biogeographic analysis of Philotheca (Rutaceae) and allied genera( 2001)This thesis considers the relationships, classification and historical biogeography of the related Australian endemic flowering plant genera Philotheca, Eriostemon and Crowea (family Rutaceae, tribe Boronieae). It focuses mostly on relationships within and between these genera, but also considers the relationships of these groups to other members of the tribe Boronieae, particularly the small genera Geleznowia and Drummondita. It includes a brief appraisal of the species-level taxonomy of Philotheca, Eriostemon and Crowea, a survey of morphological characters, a survey of leaf phenolic compounds, and a series of cladistic and biogeographic analyses. The appraisal of species-level taxonomy identified terminal taxa suitable for use in cladistic analyses, and has resulted in the recognition of one new species (Philotheca sporadica) and three new subspecies (P. myoporoides subsp. brevipedunculata, subsp. euroensis, and subsp. obovatifolia, as well as a recommendation to reinstate one species (Eriostemon banksii, which was previously reduced to subspecific status under E. australasius). The survey of morphological variation identified 108 morphological characters, 99 of which are potentially useful in the assessment of relationships, and nine that are unique to single terminal taxa. The survey of leaf phenolics was based on two-dimensional paper chromatography, and the chromatographic properties and distributions of 26 compounds are reported. Twenty-three of these compounds are potentially useful in the assessment of relationships, and three are unique to single terminal taxa. Assessment of the higher-level relationships of Philotheca, Eriostemon and Crowea (to each other and to other taxa of Boronieae) was based on reappraisal, and re-analysis, of a previous phylogenetic analysis (Armstrong 1991). This reappraisal was based on a limited set of morphological characters, and used genera, sections within genera, and some species as terminal taxa. In general higher-level relationships of the three genera were either poorly resolved or poorly supported. A close relationship of Drummondita to Philotheca sect. Philotheca was supported, but a close relationship of Geleznowia to this group (as has recently been proposed) was not. A series of subsequent analyses of relationships within Philotheca, Drummondita, Eriostemon and Crowea employed a larger set of morphological and phenolic characters (in various combinations), and used species, subspecies and varieties as terminal taxa. Character state transformations were polarised using Crowea as an outgroup to Philotheca, Drummondita and Eriostemon, and vice versa. This assignment of ingroup/outgroup relationships was based on an a posteriori decision, given the lack of a well-supported higher-level phylogeny for the group. These subsequent analyses provided good support for the monophyly of each of Crowea, Philotheca sect. Erionema, P. sect. Corynonema, P. sect. Cyanochlamys, Eriostemon, Drummondita, and a group comprising both Drummondita and P. sect. Philotheca. Philotheca sect. Philotheca was only supported as monophyletic in some analyses. Relationships among these groups were not unequivocally resolved, but the monophyly of Philotheca, as currently circumscribed, was not supported. The biogeographic analyses used the method of subtree analysis and considered the historical relationships of areas in south-western and eastern Australia. The pattern or area relationships was not unequivocally resolved, with some areas showing multiple relationships. The results of these analyses are compared with those from other studies on Australian biogeography. A general historical scenario for the differentiation of taxa and areas is discussed.
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ItemAspects of the reproductive biology, breeding system and horticultural improvement of the genus pandorea( 1992)The Australian flora represent a potential genetic resource for the production of new cultivars for the local and international ornamental plant industry. The genus Pandorea contains four species in Australia. All are climbers with a range of flower colour and size. This study aimed initially to collect a range of genotypes from the Australian species of Pandorea. It then sought to identify and study aspects of the reproductive biology and breeding system of the genus Pandorea. It also aimed to cross species using the basic techniques of plant breeding to provide unique genetic combinations as a basis for new horticultural varieties of Pandorea. Floral dimensions were measured and compared for all species. The reproductive biology was indicative of a genus comprising obligate outcrossing individuals. Strong self-incompatibility was found in three species. The fourth was not tested. The stigmas were receptive prior to anthesis. Pollen viability deteriorated over a five day period. Interspecific hybrid seedlings were obtained for some crosses through embryo culture. Embryos aborted if left on the parent plant apparently due to endosperm failure. The success of rescuing interspecific hybrid embryos was related to the stage at which embryo development was arrested. Well-developed cotyledonary embryos were readily grown in aseptic culture and were acclimatized with ease from tissue culture. Less mature embryos germinated precociously and failed to continue through the normal embryo development. Isozyme analyses were useful for corroborating the hybrid status of some putative hybrid seedlings produced in this study. One hundred and seventeen confirmed interspecific hybrids and seven unconfirmed hybrids have been acclimatized to standard nursery conditions. They are anticipated to flower for the first time in the 1994 flowering season when their floral characteristics can be assessed for horticultural potential.
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ItemRestoration of a native grassland inhabited by Synemon plana (Lepidoptera)( 1997)Synemon plana is a diurnal moth belonging to the family Castniidae in the largest insect order Lepidoptera. The habitat is typically an open-woodland or grassland. In 1995 Synemon plana was listed as endangered under the Victorian Flora and Fauna Guarantee Act 1988. This thesis investigated the habitat of Synemon plana, including the germination requirements of the host plant (Danthonia), the size of the population at Mount Piper, Broadford, Victoria and the percentage cover of Danthonia preferred by Synemon plana. Fourteen sites were investigated and sites inhabited by Synemon plana and two historical locations (sites that once supported populations of S. plana) were compared. Floristic and soil surveys showed that the habitat of S. plana was a native grassland dominated by Danthonia, in particular, D. carphoides, D. auriculata, D. setacea, and D. eriantha. The percentage cover of Danthonia at all sites inhabited by S. plana was greater than 40%. While soil chemistry was variable among sites, the concentration of available P was low (less than 14 µg/g) in all sites inhabited by S. plana. The concentration of available P and the percentage cover of weeds at the two historical locations (Flowerdale and Tallarook) were significantly greater than those at the current locations. To determine the effects of weeds on the growth of Danthonia in soils to which P has been added, Danthonia eriantha and Lolium perenne were grown together and on their own in pots. The growth of Danthonia was significantly reduced when grown with L. perenne. Whilst the growth of L. perenne increased with increasing concentrations of P, the growth of Danthonia grown on its own was not significantly different when P was added. Therefore, L. perenne was at a competitive advantage when grown in soils to which P was added whilst the growth of D. eriantha was unaffected. The percentage cover of weeds was greater in soils with greater concentration of available P. Thus in soils to which P has been added, weeds reduce the growth of Danthonia and hence result in the loss of habitat for S. plana. A number of techniques aimed at increasing the cover of Danthonia eriantha in the field at Mount Piper was trialed over twelve months. The greatest increase in the cover of Danthonia was achieved when seedlings were planted in the field and weeds were removed. Although scattering caryopsides on the surface of the soil and removing weeds increased the cover of Danthonia eriantha, a large number of caryopsides was required due to the low number of viable seeds and low germination in the field. The population size at Mount Piper was investigated over two consecutive years. Mark-Release-Recapture methods to determine absolute population size were trialed. However, capturing and marking individuals affected their behaviour and of the 22 individuals captured using this method, 14 died. A new methodology, less detrimental to individuals was employed using tents to determine absolute population size. Tents were erected over quadrats with different percentage covers of Danthonia and moths were captured as they emerged. Eleven individuals (6 males and 5 females) were caught in tents with greater than 40% cover of Danthonia. Transect methods to determine relative population size were also investigated over two seasons. The total number of individuals counted over the 1995/96 and 1996/97 flight season was 311 and 183. The variability in the number of S. plana observed along the transect route during 1995/96 and 1996/96 was probably due to the high rainfall during August to December in 1996 which increased the mortality of the larva in the soil and hence reduced the number of S. plana emerging. All but three individuals were males and therefore the transect technique overwhelmingly selects for males. Assuming a 1: 1 sex ratio then the adult population is estimated to be between 300 and 700 individuals occupying an area of 1500 m2. There was a good relationship between the rate of emergence within the tents and the number of individuals observed using the transect method. The use of tents therefore provided an indication of population size, showed that the sex ratio of Synemon plana was 1: 1 and that the cover of Danthonia preferred by the moth was greater than 40%. To restore the habitat of Synemon plana, and hence to maintain a viable population, the cover of Danthonia must be increased to greater than 40% covering an area greater than 1500 m2 . Seedlings should be planted in autumn and weeds removed. Competition from weeds must be eliminated to increase the percentage cover of Danthonia in the field.
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ItemThe ecology of Agrostis spp. (bent grass) invasion into temperate pastures( 1996)The grass, commonly called 'bent grass', has been rated by meat producers and consultants working in industry as one of the worst weeds of perennial grasses in temperate pastures in Victoria. Bent grass in Victorian pastures has traditionally been identified as Agrostis capillaris. However it has become clear that Agrostis castellana rather than A. capillaris is predominantly found in Victorian pastures. Management techniques to reduce the proportion of A. castellana in pastures must be modified based on the assumption that we are dealing with A. capillaris. The vegetative morphology of A. castellana populations sampled from diverse locations within Victoria was similar. A. castellana spreads vigorously by rhizomes which will reduce the success of presently-accepted management techniques (e.g. mob stocking) but will enhance the success of techniques that focus on reducing the rhizomatous capability of A. castellana. Flowering times differed between A. castellana populations such that genotypes of populations from drier climates completed flowering earlier or within a shorter time than genotypes from other populations. Techniques which focus on preventing floral development (e.g. spray-topping) will require refinement for different locations in Victoria. The cost of renovation combined with limited success to reduce the proportion of Agrostis spp. in the long term (> 10 years) has reduced the adoption of pasture renovation in some areas. Agrostis spp. regenerated from seedlings after pasture renovation, at variance with general conceptions. Thus pasture renovation techniques must reduce the regenerative ability of Agrostis spp. from seed. Agrostis castellana regenerates from viable rhizome fragments remaining after cultivation, in addition to seedling regeneration. Rhizomes of A. castellana displayed apical dominance in that lateral buds on rhizomes remain dormant. Presently-accepted pasture renovation does not take into account the fact that apical dominance in rhizomes ensures continuative regeneration. The technique of pasture renovation must ensure that the regenerative ability of bent grass is severely reduced, and this was achieved when rhizomes were broken into small 1-node fragments, buried beyond 75 mm and a rapidly establishing pasture sown. The dominance of bent grass in pastures indicates that bent grass competes successfully with other pasture species under current agricultural practices in Victoria. The mechanism of competition under A. castellana-dominant pastures supported the resource competition theory in that a greater proportion of the nitrogen absorbed under A. castellana pasture remained in the roots than in shoots, reducing the availability of nitrogen to be re-cycled in faeces and urine by the animal. Thus a greater proportion of nitrogen was returned by plant death and decomposition in A. castellana-dominant pasture than in L. perenne-dominant pasture. Decomposing shoots, roots and rhizomes are slow to release mineral nitrogen which is confirmed by reduced gross mineralization and reduced concentrations of nitrate in soil solution under A. castellana-dominant compared with L. perenne-dominant pasture. N uptake by A. castellana was as nitrate, in preference to ammonium, further depleting the concentration of nitrate in soil solution. When L. perenne grows in association with A. castellana, plant nitrate requirements are unlikely to be met and L. perenne pasture may then degrade to A. castellana-dominance. The likelihood of A. castellana dominance in L. perenne pastures may be reduced by improving litter quality and rates of mineralization.
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ItemHyperaccumulation of metals in Australian native plants( 2000)The central aim of this thesis was to study the accumulation of metals in Australian native plants. Firstly, this involved searching for new hyperaccumulators on serpentine outcrops in the Wellington region of Victoria and serpentine areas between Rockhampton and Marlborough in central Queensland. A new hyperaccumulator of Mn was found in central Queensland, Austromyrtus bidwillii. This is the first Australian native plant to be reported to hyperaccumulate Mn. Manganese accumulated throughout the above-ground parts of this dry rainforest tree, reaching concentrations up to 19,200 µg g-1 and 26,500 µg g-1 in leaves and young bark, respectively. Concentrations of Ni, Cr, Co, Mn, Mg and Fe in the other species sampled were generally either lower than or similar to the concentrations reported to be typical for serpentine vegetation throughout the world (96 species were sampled from Victoria and 138 species from central Queensland). The aim of the second part of this thesis was to examine possible mechanisms involved in detoxification of metal ions and storage of metal complexes in two known hyperaccumulators of Ni from Australia, Hybanthus floribundus and Stackhousia tryonii, and the hyperaccumulator of Mn identified in the surveys described above. This involved identifying and quantifying organic acids present in leaf extracts and determining whether there were sufficient concentrations of these compounds to sequester the metal. In leaves of Austromyrtus bidwillii, a number of organic acids (oxalic, malic, malonic and succinic acids) were present in relatively high concentrations compared with normal plants and the total concentration of organic acids exceeded the concentration of cations (Mn, Mg and Ca). Purification of the Mn rich extracts of leaves by size exclusion chromatography showed that these organic acids could be associated with the Mn. In both Stackhousia tryonii and Hybanthus floribundus, citric acid was the dominant organic acid present in leaf extracts, but it was present in concentrations that are considered as normal for plant leaves. The effect of treating plants with Ni on citric acid content in leaves and roots of Hybanthus floribundus was investigated. Ni treatment had no significant effect on citric acid content in leaves, but a strong and significant correlation was found between Ni and citric acid content in roots. Citric acid was present in sufficient concentrations in both leaves and roots to complex the Ni in most treated plants, except for those treated with the highest dose of Ni. Similarly, in field samples that contained very high concentrations of Ni (collected from Widgiemooltha, W A), there was insufficient citric acid to complex a significant portion of the Ni. The cellular and sub-cellular distribution of Ni in the two Ni hyperaccumulators was investigated using x-ray microanalysis. In leaves of Hybanthus floribundus, Ni was predominantly localised in the vacuoles of epidermal cells, averaging 128 lnmol kg- l of embedded tissue. Ni was also detected on the outside of the cell walls throughout the leaf cross sections, suggesting that apoplastic compartmentation is also involved in Ni tolerance and accumulation in this species. In leaves of Stackhousia tryonii, Ni was predominantly localised in the cuticle on the surface of the leaf and was also present in epidermal vacuoles. In both species, there was no indication that Ni was associated with phosphates or phytochelatins, as concentrations of P and S were insufficient to suggest an involvement in sequestration of Ni. Thirdly, a protocol for the micropropagation of Hybanthus floribundus was developed, as the germination requirements of seed of this species are unknown and propagation from cuttings is slow and has low efficiency. Large quantities of plants were successfully grown in culture from sterilised pieces of stem or leaf tissue. Importantly, cloned plants retained their ability to hyperaccumulate Ni. Micropropagation provides many opportunities for studying metal tolerance and hyperaccumulation of Ni in this species in the future. Moreover, the protocol presented in this thesis may be used for cultivation of Hybanthus floribundus for rehabilitation of mine sites or perhaps for phytoextraction. Finally, the ability of Hybanthus floribundus ssp. floribundus growing on non-metalliferous soil in Bendigo, Victoria, to hyperaccumulate Ni was investigated. Plants hyperaccumulated Ni when grown on Ni-enriched potting mix, with no adverse effect on growth or nutrient status. This finding suggests that hyperaccumulation of Ni in this species may not be restricted to the populations that grow on serpentine in Western Australia.
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ItemMolecular and morphological systematics of Hovea and the Brongniartieae (Fabaceae)( 1999)Hovea is a small genus of mostly mauve or purple-blue flowered shrubs and is a member of the tribe Brongniartieae (Fabaceae). It has a widespread distribution in semi-arid to mesic parts of all states and territories of Australia with two main centres of diversity: the east and the south-west. Satisfactory classification of eastern state forms has proved elusive. A conservative treatment by Bentham in Flora Australiensis (1864) meant that much of the apparent diversity was concealed for the following 120 years. Recent work has recognised more of this diversity but major problem areas were still to be addressed. Morphometric analysis of eastern hoveas revealed a pattern of diversity which provided the basis for a revised classification, largely involving the splitting up of two species complexes. Sixteen species and one sub-species are to be described as new and a further species is to be resurrected in this new classification. Since 1987, the Brongniartieae has comprised four Australian genera and two tropical American genera. Prior to this, however, the Australian genera, Hovea, Templetonia, Lamprolobium and Plagiocarpus, had, at various times, been placed in the Australian tribe Bossiaeeae. Morphological data used to recircumscribe the Brongniartieae (Crisp and Weston, 1987) were conclusive but intratribal relationships were poorly resolved. Nuclear DNA sequence data (ITS-I region of the 45S rDNA cistron and the 5S rDNA gene and spacer region) and new morphological data were used for phylogenetic studies of the Brongniartieae. Sequence variability in the 5S spacer region made alignment difficult and limited the usefulness of this region, particularly for higher level relationships. For the ITS-l region, alignment was largely unambiguous but information content was relatively low. The monophyly of the Brongniartieae was supported by these data. The two molecular phylogenies, derived using parsimony methods, were reasonably congruent and consistency was high in both instances. The morphological data were moderately congruent with the two molecular data sets and was informative for some nodes where molecular data were lacking. Combining molecular and morphological data resulted in a well-resolved phylogeny
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ItemThe autecology of Callitris collumellaris F. Muell. and associated eucalyptus spp. in south-eastern Australia( 1981)This thesis investigates the ecology of C.columellaris in south-eastern Australia under three main areas of research; descriptive field ecology, experimental field ecology and experimental ecology of seedlings. Since C.columellaria in Australia rarely forms pure stands over large areas comparative studies involving some or all Eucalyptus species (E.albens, E.melliodora and E.microcarpa) with which it commonly occurs have been made in each research area. Field work was undertaken at two principal locations, Savernake, NSW and the lower Snowy River area. Supplementary data was also collected from Mitiamo in central Victoria. The two principal areas of study are typical habitats of C.columellaris, but provide a contrast in topography and associated species. In the text frequent reference to juvenile foliage will be made, particularly with respect to C.columellaris. A short discussion, with illustrations, on juvenile and adult foliage can be found in Appendix I. All nomenclature in this thesis is according to Willis (1972, 1973), unless otherwise cited.
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ItemThe taxonomy, life history and cytology of Bryopis and related genera from Southern Australia( 1974)Three genera, Bryopsis, Derbesia and Pedobesia, have been studied in the field, in culture and through carefully correlated light and electron microscopy. Three species of Bryopsis are recognised; B.vestita, B.plumosa and B.gemellipara. These are described by combinations of characters which can be easily determined in field populations. Additional descriptions are given of the cytology, life histories and interfertility of these species and the genera Derbesia and Pedobesia. The study shows a close similarity between the three genera, which are classified within the Derbesiales.
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ItemThe infection process of Fusarium oxysporum f. sp. vasinfectum in Australian cotton and associated cotton defence mechanisms( 2007)Fusarium oxysporum f. sp. vasinfectum (Fov) was first identified in Australia in 1993, and has since become one of the most significant threats to the country’s thriving cotton industry. The interaction between a unique Australian biotype of Fov and cotton hosts with varying susceptibilities to Fusarium wilt was studied. This research described the infection process and associated host defence mechanisms of two commercial cotton varieties after inoculation with Fov, and quantified their subsequent accumulation of antimicrobial terpenoids. A rapid, reliable glasshouse bioassay that correlated with field resistance was developed for the study of Fusarium wilt of cotton. Detailed observations of the infection process obtained through light microscopy were used to formulate the disease cycle of Australian Fusarium wilt cotton. Using pathogen growth assays, varietal differences in root exudates and vascular tissues in the cotton hosts were documented. Root diffusate from the most susceptible cotton variety to Fusarium wilt, Siokra 1-4, contained a lipophilic compound that promoted the germination of Fov microconidia. On the other hand, a lipophilic compound present in diffusate from the least susceptible variety, Sicot 189, inhibited the growth of Fov germ tubes. A bioassay using inoculated whole plants showed that Fov colonisation of the vascular tissues of Sicot 189 was restricted after 3 days. The basis for this inhibition was investigated further using light and transmission electron microscopy. Infection induced the reorganisation of contact cells in host vascular tissue, including an increase in cytoplasmic content and the partitioning of vacuoles, which was concurrent with the accumulation of materials in adjacent vessel lumens, via pits. Histochemical analysis indicated these globular materials secreted into the vessels were terpenoids. These structural and terpenoid responses in Siokra 1-4 and Sicot 189 were similar, however, they were more intense and rapid in the latter, less susceptible variety. The responses in Sicot 189 also corresponded to the time period that pathogen inhibition was observed. Thus, a correlation was demonstrated between the rapid and intense induction of both structural and biochemical responses with decreased susceptibility to Fusarium wilt. Detailed HPLC analysis of vascular tissues confirmed that terpenoids accumulated more rapidly and at higher concentrations in the less susceptible cotton variety. These findings provided strong evidence for the involvement of antimicrobial terpenoids in the determination of Fusarium wilt susceptibility of Australian cotton varieties. This work represents the most complete survey to date of the interaction of Australian biotypes of Fov with cotton. These insights can contribute to future cotton breeding efforts and cultural management of Fusarium wilt in the field. Thus, each part of this study has advanced complementary facets of our understanding of Fov, and has provided a framework from which future studies on phytoalexins and other putative cotton defences can be studied.