School of Botany - Theses
Permanent URI for this collection
Search Results
1 - 10 of 11
-
ItemStudies on the flagella and cytoskeleton of pleurochrysis carterae (prymnesiophycae) and mallomonas splendens (synurophyceae)(University of Melbourne, 1989)The flagellar apparatus of motile, coccolith-bearing cells of Pleurochrysis carterae (Braarud & Fagerlund) Christensen (Prymnesiophyceae) and that of Mallomonas splendens (G.S.West) Playfair (Synurophyceae) are described at interphase and during cell division. The interphase arrangement of the flagellar apparatus in Pleurochrysis carterae is similar to that in Pleurochrysis sp. (Inouye & Pienaar 1985) but I report new information on microtubular root 1 (R1) and describe in detail the transition region of the flagellar axoneme. The basal body of the longer flagellum is shown to be that which is associated with R1. A distinctive membrane decoration is noted on specific areas of the peripheral endoplasmic reticulum (PER) and I discuss the role of the PER in scale secretion and endocytosis. The basal bodies of P. carterae duplicate before mitosis and the crystalline roots (CRs), which arise from R1 and root 2 (R2), disassemble at prophase as their component microtubules elongate towards the future spindle poles. By late prometaphase the basal bodies have segregated semi-conservatively and each pair displays diminutive flagellar roots for the future daughter cells. The two parental basal bodies now bear R1s, indicating that the basal body that produced a short flagellum in the parental cell has transformed into one that will produce a long flagellum in the daughter. All flagellar roots assume their interphase appearance by early cytokinesis. Amputation of the flagella of P. carterae results in their immediate regeneration according to deceleratory kinetics. In the presence of 1?g/ml cycloheximide flagella regenerate to only c. half-length. Immunofluorescence microscopy shows that CRs diminish in size as flagella regenerate and, in the presence of cycloheximide, are depleted when flagella cease to elongate. These data indicate that a pool of presynthesized precursors is available for flagellar regeneration in P. carterae and that part of this pool consists of tubulin from the CRs. Cells of Mallomonas splendens bear a single emergent flagellum (F1) and a non-functional basal body (F2). Direct observations on dividing cells show that the FIs of daughter cells arise from newly formed basal bodies as the parental F1 retracts and thereby transforms into a new F2; the parental F2 remains as such for successive generations. These results are confirmed with thin-sections. The flagellar apparatus of M. splendens at interphase displays numerous features that are novel in the Synurophyceae: the basal bodies are surrounded by a distinctive fibrous capsule; this is continuous with a thick, fibrous band that constitutes the anterior portion of the rhizoplast; the posterior of the rhizoplast forms a cone of numerous, striated straps over the nuclear apex; a single (three-membered) microtubular root (R1) is present which forms a loop around the basal bodies and descends to terminate on the rhizoplast near the nuclear apex; the descending portion of R1 has at least two orientations with respect to the basal bodies. The development of these structures is described from dividing cells. The R1s and rhizoplasts for daughter cells are formed de novo in association with new basal bodies at early mitosis as the parental structures disassemble. The new rhizoplasts are the organizing centres for the mitotic spindle. Mitosis in M. splendens is compared to that in the Chrysophyceae. The final chapter deals with the deployment of the four posterior bristles in M. splendens. Bristles articulate at their flexed basal ends, via an attached fibrillar complex, on specialized body scales (base-plate scales). Bristles are formed independently of their base-plate scales and I describe how they are united outside the cell. Mature posterior bristles are secreted onto the plasma membrane at late interphase and then extruded, basal ends first, from beneath the layer of body scales. Once bristles are fully extruded they are drawn back to the posterior apex of the cell with their basal ends leading - thus a 180� reorientation of the bristles has been effected outside the cell. A cytoplasmic protuberance which contains at least one microtubule accompanies the bristles throughout this reorientation and I propose that it is intimately involved. The fibrillar complex is formed in situ on the bristles and appears to mediate the deployment of bristles onto new base-plate scales.
-
ItemAspects of the water relations of eucalyptus behriana F. muell. and E. microcarpa (maiden) maiden near Melton, Victoria(University of Melbourne, 1985)
-
ItemStudies on the distribution and cycling of nitrogen in forests(University of Melbourne, 1982)
-
ItemA taxonomic study of the genus Nostoc in Antarctica(University of Melbourne, 1981)This thesis provides written descriptions and illustrations of Antarctic specimens of Nostoc from both field and cultured material. The aims of the project were to provide the first detailed morphological descriptions of Nostoc from Antarctica and to assess the three different taxonomic approaches currently in use for this genus and for blue-green algae in general. Eight samples of field material are shown to consist of colonies of just two distinctly different structures. Clonal cultures obtained from all of these are described in detail using defined, standardized culture conditions. Five morphologically distinct strains have been recognized from these eight samples. Additionally two distinct strains, previously isolated from field material of unrecorded morphology, have been incorporated into the study. Detailed observations on the morphology and life-cycles displayed by cultures have been made over a 12 week period. Seven genetically distinct strains are distinguished, essentially by plant-mass appearance, although microscopic characters are of importance in some. Two basic types of life-cycle are elucidated, one of which differs from those previously described in the literature. A key is presented which allows the identification of Nostoc strains in culture using these characters. An attempt is made to identify the isolates, and the field material from which they were derived, using three taxonomic approaches. The classical system (Geitler, 1932) is useful only on the field material which is assigned either to N. commune Vauch. or as being close to N. sphaericum Vauch. and N. fuscescens Fritsch. The revised classical system proposed by Drouet (1978) identifies all field and culture material as N. commune (Vauch.) Drouet. Some close correlations are made between cultured strains and those examined in culture by Kantz and Bold (1969). It is concluded that none of these three taxonomic approaches is without its problems and shortcomings and presently no correlation can be made between them. A programme for future work is suggested which might be able to overcome these difficulties and which would lead to an even greater understanding of the important Antarctic genus, Nostoc.
-
ItemNo Preview AvailableThe effects of sewage effluent on the macrophytes off Werribee, Port Phillip Bay(University of Melbourne, 1980)
-
ItemAspects of the biology and ultrastructure of prorocentrum spp. (pyrrhophyta)( 1987)Ultrastructural characteristics were evaluated as taxonomic determinants for several species of dinoflagellates in the Prorocentrales (Pyrrhophyta). Five species of Prorocentrum from several localities were examined using the techniques of light and electron microscopy. The organisms were described and identified by light microscopy, and certain internal features of Prorocentrum spp. cells were described using transmission electron microscopy. Specifically, the.ultrastructure of the nucleus, cytoplasm, vesicles, pusules, trichocysts, mitochondria, chloroplasts, pyrenoids, cortex (cell wall) and flagellar apparatus was examined in these organisms. The structure of the cortex in P. gracile was also examined by the technique of freeze fracture/deep etch. Most organelles were found to vary little between taxa. The ultrastructure of a few organelles, namely the pyrenoids and some features. of the cortex, varied considerably between species and are therefore considered taxonomically more useful than others. The morphology of the chondriome (mitochondrial complement) of P. minimum was established using the technique of serial sectioning. It was found to consist of a major reticulated mitochondrion and several smaller satellite mitochondria. During cytokinesis, the major portion of the chondriome is split by the cleavage furrow and approximately half of the chondriome is passed to each daughter cell. The significance of this structure and the division mechanism is discussed (Chapter Three). Aspects of the processes of mitosis (karyokinesis) and cell division (cytokinesis) are described in P. gracile and P. minimum. Both species were found to have a closed mitosis, the nuclear membrane being strongly associated with the chromosomes, and microtubules traversing channels through the nucleus, as observed for other members of this group. Kinetochore-like structures may occur in these organisms. A cell of P. gracile undergoing division is also illustrated (Chapter Four).
-
ItemAspects of shrub-grass dynamics on the Bogong High Plains (Subalpine), Victoria( 1985)The Bogong High Plains are a series of alpine and subalpine plateaux in NE Victoria. The vegetation of the High Plains consists of woodland, heathland, grassland herbfield and wetland communities. On the better drained sites, the transition from heath dominated communities to grass dominated communities is correlated with gradients of decreasing accumulation and persistence of snow, increasing exposure to wind and low minimum air temperatures, and decreasing steepness and rockiness of terrain. In many areas, shrubs have increased in cover and abundance, especially over the last 50 years. In particular, shrubs have invaded many areas of grassland, which has resulted in an expansion of both open heath and closed heath. The High Plains have been grazed by free ranging cattle each summer since the 1850's, and a primary aim of this thesis is to investigate the dynamics of heathland and grassland, and the impact that cattle grazing has upon these two vegetation types.
-
ItemNumerical analyses of macrophyte vegetation in Victorian wetlands in relation to environmental factors( 1984)This study was undertaken to investigate the variability of vegetated Victorian wetlands and to establish the relationships between this variation and major environmental factors. Criteria for the selection of the 55 wetlands sampled included the presence of aquatic macrophyte or helophyte vegetation, the presence of at least an intermittent water body and, comparative lack of disturbance of the site. Sites were also chosen to reflect the considerable lithological and climatic variation found across lowland Victoria. At each site, species presence/absence data, water depth and water transparency were recorded within 1m square quadrats positioned at 5m intervals along transects located to best sample the vegetation. At each transect, water samples were collected for the analysis of major ions, and substrate samples were taken for the estimation of texture and measurement of pH and percentage salts. The maximum depth of the basin when flooded and its water regime were estimated and the geology and rainfall of the catchment were recorded. An information statistic strategy was used to classify the large, relatively sparse floristic set of data. The classification recognised five distinctive, relatively homogenous and ecologically interpretable groups of wetlands, which were characterised as having saline, very saline, turbid, acidic or calcareous waters, and a further three freshwater groups which were closely related to one another. The application of data reduction techniques suggested that the information statistic model was unable to adequately define some of the freshwater groups of sites primarily because of the highly heterogenous nature of the data set. Two more data sets were produced by deleting species with low "eident" values (Dale and Williams 1978) and by deleting species regarded as terrestrial. However, classification of these reduced data sets did not provide markedly better results. The relationships between the groups (and their members) generated by classification was examined through indirect ordination of the floristic data. Inspection of the results indicated that six of the eight groups identified by classification of the floristic data could be recognised. However, two groups of saline sites could not be separated, largely because they were both species-poor. Six sites were identified as the probable cause of overlap of some of the freshwater groups. Laboratory determination of the major ionic constituents of the waters of the 55 wetlands indicated that the orders of anion dominance were Cl>HC03+C03>S04 (freshwater sites) or Cl>S04>HC03+C03 (saline and coastal freshwater sites) and those for cations were Na>Mg>Ca>K or Na>Ca>Mg>K (freshwater) and Na>Mg>ca>K (saline sites). The dominance of chloride and sodium ions in the waters sampled suggested that salinity was a major factor affecting the distribution of aquatic macrophytes in Victoria. Numerical classification of the wetlands on the basis of their water chemistry was undertaken to provide a comparison with the eight group floristic classification. However, two of the intuitively recognised groups, the turbid and calcareous waters, were not identified by classification of the water chemistry data, and membership of the two independently generated sets of groups was not identical. The nature of the hypothesized joint pattern between the floristic and the water chemistry data was further investigated by canonical correlation analysis, analysis of variance and discriminant analyses. These analyses confirmed that overall, the variance observed in the vegetation of the wetlands sampled was significantly influenced by water chemistry. However, the level of vegetational variation identified as a result of classification of the floristic data (eight groups) did not correspond well with the measured differences in the water chemistry variables. Vegetation differences which could be attributed to water chemistry differences were those between the saline groups, the turbid water group, the acidic water group, the freshwater complex of three groups, and possibly the calcareous group. The salinity variable largely separated the saline groups from the rest, whilst pH separated the acidic water and calcareous water groups from each other and the freshwater complex. The turbid water group was separated by a combination of pH and salinity variables. An evaluation of the methods used is presented and other factors which may be important in explaining the heterogeneity of the saline and freshwater floristic complexes are discussed. The wetland vegetation sampled in Victoria is compared with the plant communities of Tasmanian wetlands.
-
ItemThe early land flora of Victoria( 1980)A re-examination of existing collections together with detailed examination of material from four sites in the Early Devonian (Pragian/ Siegenian and provisional Late Silurian (Ludlovian) rocks of Victoria has considerably extended the geographic range of the known genera and added a significant number of new taxa to the Baragwanathia flora. This survey further confirms that the early land flora was comprised not only of the simplest types of vascular plants (the Rhyniophytes) but also plants of increasing complexity, the Zosterophylls, Lycophytes and Trimerophytes. The flora has a number of forms clearly closely related to plants from strata of the same age of the northern hemisphere. Ten new species are described, together with descriptions of fragmentary remains of at least ten others as yet too incomplete to be given formal status. Two new species of Salopella, a genus previously known only from the northern hemisphere, and a new species of Hedeia are new Rhyniophytes recorded for the first time. The Zosterophyllophytina is further represented by two new genera, Pluricaulis and Chamaecaulon, and a new species of Zosterophyllum. A second small and two other probably distinct species have been added to the genus Baragwanathia which together with a new plant with rhizophores, are members of the Lycophytina. Although represented only by one small fertile branch, a new species of Dawsonites, provides evidence that the Trimerophytina was also present in this flora. The presence of a portion of this flora, including the relatively complex Baragwanathia in rocks provisionally assigned by some geologists as Ludlovian, poses some unusual problems, as plants of this age in the northern hemisphere are only of the very simplest kind.
-
ItemThe effects of high temperatures on the growth and physiology of E. obliqua L'herit seedlings( 1981)The responses of plants to high temperatures depend on both their level and duration. These studies on the effects of high temperatures on the growth and physiology of Eucalyptus obliqua seedlings reveal that the method of applying heat is also important. The quantitative assessment of plant condition has been achieved by electronic means and the use of pigment analyses. E. obliqua seedlings possess heat avoidance mechanisms and they are capable of surviving severe stress. In some instances their growth is enhanced. If damaged, the potential for E. obliqua seedlings to recover, is facilitated by the presence of a lignotuber. The eucalypts are renowned for their ability to survive stress and the responses of E. obliqua seedlings to high temperatures conform to this reputation.