School of Botany - Theses
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ItemRole of Ribulose-1,5-Bisphosphate Carboxylase(University of Melbourne, 1998)Physiological adaptations by plants in order to better utilise sunflecks were studied using plants from the rainforest understorey. Transgenic Rubisco and wild-type Nicotiana tabacum L., from the Solanaceae family, were used to model these adaptations and to better characterise the light induced activation kinetics. Tobacco plants with varying Rubisco concentrations were used to obtain plants with differing Activase to Rubisco stoichiometry. An increase in the stoichiometry caused proportional changes in the rate of Rubisco activation. This was reflected in a decrease in the relaxation times from 2.5 to 3 minutes down to 35 to 40 seconds. This faster rate of activation lead to a reduction in the amount of C02 assimilation effectively forgone due to the activation process. In wild-type tobacco this amount of forgone photosynthesis was found to be, on average, 23.5 ?mol C02 m-2 compared to 6.0 ?mol C02 m-2 for Rubisco mutant tobacco plants. Understorey plants from the rainforest of Cape Tribulation National Park (QLD) were examined to see if they adjusted their stoichiometry of Activase and Rubisco in order to increase C02 assimilation in sunflecks. Gas exchange analysis of the rainforest plants showed them to behaved in a similar fashion to the Rubisco mutant tobacco. Examination of the kinetics of Rubisco activation in rainforest and Rubisco mutant tobacco plants found, on average, comparable relaxation times (58 and 67 seconds, respectively) and similar initial activation rates (46.6 and 46.1 nmol active sites m-2 s-1, respectively). When compared to wild-type tobacco, the rainforest plants on average were found to have over 5.5 times the ratio of Activase to Rubisco. This leads to a reduction in the average amount of forgone photosynthesis from 23.5 ?mol C02 m-2 for wild-type to 4.2 ?mol C02 m-2 for rainforest plants. These results suggest that plants grown under fluctuating light environments alter their stoichiometry in order to better utilise sunflecks for carbon gain.
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ItemInvestigations into the mechanisms of morphogenesis in Desmids(University of Melbourne, 1994)Whether a neuron in a mammalian brain or a guard cell from leaf stomata, the shape of a cell is often vital to its function. Yet morphogenesis, the 'creation of form', is one of the least understood phenomena in cell biology. In order to understand the processes behind morphogenesis, it is reasonable to select a simple organism in which to initiate an investigation. Once this system is understood, the knowledge and concepts may then be applied to other, more complex organisms. The potential of desmids, a group of freshwater green algae from the order Zygnematales (Fritsch 1935), for the study of morphogenesis was first recognised by Waris (1950). There are several reasons why the desmids are particularly well suited for investigation of morphogenesis: the cells are large, making them easy to observe and handle; the asexual lifecycle is predictable and can be completed in 3-8 days; they can be grown in simple inexpensive media; they are found all around the world; and, perhaps most importantly, they display elaborate symmetrical cell patterns which are reproduced every division.
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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.
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ItemNo Preview AvailableThe estimation of indole-3-acetic acid(University of Melbourne, 1979)This project evolved from a consideration of polarity in the embryo of the brown alga, Hormosira banksii. It was hypothesized that uneven distribution of auxin due to unilateral illumination led to the protrusion of the rhizoid on the dark side of the zygote. It was intended to test this hypothesis by supplying the zygotes with labelled indole-3-acetic acid and, after incubation in this medium, examine the zygotes using micro-autoradiography. The concentration of indole-3-acetic acid in the cell had to be determined in order that the radioactive compound could be supplied to the zygotes at physiological concentrations. This required the review and selection of extraction, purification and assay methods. The literature review encompasses examples of most of the types of methods in current use. Since the various methods of bioassay have many advantages, limitations and equipment requirements in common, only two methods are described. As the same can be said for other types of methods, these are not considered in detail. The literature review is directed at the researcher seeking a method for the assay of auxin, and, to this end, key references are cited to enable the worker to gain more information. On consideration of the equipment available, the method using the fluorescence of 2-methyl indole-?-pyrone appeared the most suitable. For purification, chromatography using a column of polystyrene resin seemed feasible. Finally, methanol, a widely-used solvent, was selected for extraction. The assay method was examined first, as the quality of extraction and purification could then be determined using the assay. Similarly, the purification was examined prior to the method of extraction. In assessing the capabilities of the methods, many problems were encountered - some peculiar to the equipment used, but several fundemental problems related to the techniques themselves. In fact, considering the findings of this work, it is apparent that the methods of auxin-assay warrant reappraisal with particular respect to losses.
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ItemA thesis presented to the University of Melbourne for the degree of Master of Science(University of Melbourne, 1949)
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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).
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ItemAn ecological study of the sub-tidal macrophytic vegetation of three selected areas of Port Phillip Bay: Werribee, Altona and Carrum; and a literature review: sewage and oil pollution in relation to macrophytic marine algae, with a short account of the "wasting disease" of the marine angiosperm Zostera( 1970)The problems of pollution, resulting from population explosion, increased technology, industry and commerce will undoubtedly be of foremost concern for present and future generations. Pollution arises primarily from the concentration of large human populations into small areas. Populations tend to condense in urban seaboard cities, and it is in such situations that the pollutionary side-effects of economic expansion are most evident. In the United States about half the population lives on the margins of the Oceans or of the Great Lakes and in Australia at least 65 percent of the populus lives in coastal cities. Early studies of aquatic pollution centred around the fresh water environment and it is only in the last two decades that the urgency of the need for more precise scientific knowledge of the biology of marine pollution has become apparent. Consequently, the literature concerned with the ecological effects of marine pollution has increased considerably in recent years, prompted in certain instances, by the lack of knowledge evident in the handling of emergency situations such as oil spillages. Such disasters have encouraged symposia, conferences and many texts dealing with facets of marine pollution ecology. More recent publications are by Fyn (1965), Olson and Burgess (1967), Smith (1968), and Carthy and Arthur (1968). These publications review the literature available on marine pollution, but although much research is now being done to ascertain the effects of pollution. on marine organisms, its effects upon macrophytic marine algae has not received as much attention as the zoobenthos, nekton and plankton which play a more important role in food chains terminating with man. Boney (1965) has written the only review to include consideration of the economic aspects of the effects of various contaminants on seaweeds. The word POLLUTION is derived from the past participle of the latin verb 'Polluere'. The Oxford English Dictionary defines 'Pollute' as follows: To make physically impure, foul or filthy; to dirty, stain, taint or foul. Definitions of marine pollution are diverse and often contentious. However, two fundamental precepts are frequently reiterated. Firstly, that marine pollution is a man-induced phenomenon - a notable exception to this being the "red tides" or blooms of poisonous phytoplankton familiar to phycologists; and secondly, that it produces a change in the biological balance of the environment that is detrimental to marine life or man.
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ItemA primary ecological survey of the Kentbruck Heath( 1970)Introduction: The Kentbruck Heath is an area in the far southwest of Victoria, about six miles in from the coast, and almost mid-way between Portland and Nelson. The flora of the area is exceptionally rich and diverse, and is relatively undamaged. The western two thirds of the area was proclaimed as part of the Lower Glenelg National Park in 1969. For these reasons it was decided to investigate it by means of a primary ecological survey. This survey occupied only 12 months, and this limited the type of work which could be undertaken. The area known as the Kentbruck Heath can be broadly delineated on a map by the Kentbruck Road and F.V.C pine plantations on the west, Inkpot Road on the north, Heath Road and Kentbruck Settlement on the east, and other agricultural development on the south. The detailed survey was restricted to a representative square mile of this, but general observations confirm the validity of some extrapolations from the data obtained. By way of comparison, an area to the west known as Bulley Ranges has also been the subject of preliminary survey.
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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.