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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Maintenance and structuring of two temperate Haliclonid sponge populations

Abdo, David A. January 2007 (has links)
[Truncated abstract] Sponges have an invaluable ecological importance through the provision of shelter and habitat, consolidation of reefs, bio-erosion, and in benthic-pelagic coupling processes. In addition, sponges are known to be an incredible source of compounds with bio-medicinal and commercial applications. Despite their ecological and economic importance, our understanding of the processes which maintain and structure sponge populations is severely lacking compared to other sessile invertebrates (e.g. Cnidarians). This study examines the processes which help maintain and the factors which structure the populations of two sympatric Haliclona species (Demospongiae; Haplosclerida; Chalinidae) at Hamelin Bay on the south west coast of Australia. In addition, the importance of both species to the broader marine community is examined. The reproductive biology of both species was determined from histological sections taken from each species over two years at Hamelin Bay. No evidence of asexual reproduction was observed in either species. Sexual reproduction occurred from November to April in Haliclona sp. 1 (hereafter green Haliclona) and November to May in Haliclona sp. 2 (hereafter brown Haliclona). The green Haliclona is viviparous with both gonochoric and hermaphroditic individuals observed in the population. The brown Haliclona is also viviparous with separate sexes. The onset and progression of reproduction in both species corresponded to increases in water temperature and photoperiod, but only decreasing wave height showed a significant correlation to gametogenesis. ... A significant (P < 0.05) difference in concentration between seasons was also observed, suggesting environmental and physiological factors affect the production of salicylihalamide A in the green Haliclona. The importance of each species to the marine environment was assessed by investigating the endofauna inhabiting each species across their known range ( [approx. ]1000 km's). A total of 948 and 287 endofaunal individuals were found associated with the green and brown Haliclona, respectively. Twenty four endofaunal taxa were found (from mysid shrimps to teleost fish), and the endofaunal assemblages of each species were significantly different. However, only the endofaunal assemblage associated with the green Haliclona varied among locations. Overall, this study demonstrates that the populations of both species are maintained by limited sexual reproductive output and larval dispersal. Abiotic factors (e.g. water temperature, wave exposure) influence the growth and physiology of both species, which is intimately connected to their abilities to reproduce. This has important consequences for the species populations with regard to their resilience to environmental change, and potential for harvesting of biomass for supply of bioactive compounds. Additionally, both species provide important habitats for many other organisms. The findings highlight the need for a detailed understanding of the ecology of potentially exploitable sponge species, to ensure their conservation and limit the impact on the organisms which rely on the sponges.
42

Residue composition influences nutrient release from crop residues

Collins, Shane January 2009 (has links)
[Truncated abstract] A greater adoption of stubble retention, minimum-till and no-till farming practices for the purposes of conserving soil, water and fertility requires a greater understanding of the complexity of physical and chemical interactions between the soil and crop residues. There is currently insufficient knowledge to allow reliable predictions of the effects of different residue types in different environments on soil fertility and crop growth, owing to the many residue characteristics and environmental interactions that have been shown to affect decomposition or nutrient release. The role of fibre and nutrient composition in nutrient release from crop residues, and implications for residue management techniques, were studied. Canola, lupin and field pea residues, obtained from farmland in Meckering and Northam, Western Australia, were separated into upper and basal stems, leaves, and siliques or pods. This was done to provide materials with a wide range of chemical and physical characteristics, and also allowed consideration of differential residue management of plant organs, such as comparing harvested canola siliques and retained canola stubble. Pre-treatment by chopping and/or humidification was applied to residues to provide some information about the processes of nutrient release. Residues were subjected to simulated rainfall to assess nutrient leaching from plant material, and placed on soil in pots in constant-temperature glasshouse conditions to assess decomposition. Amounts and rates of change of residue fibre and nutrients were determined throughout leaching and decomposition. Energy Dispersive X-ray (EDX) microanalysis was used to assess the location of diffusible ions in air-dried residues and the effects of humidification on nutrient positioning and release. ... However, the release of calcium and magnesium depended on the decomposition of the more recalcitrant components such as cellulose and lignin, as supported by microscopy results showing changes in nutrient distribution following humidification. The proportionality of amounts of calcium and magnesium leached and released during decomposition is likely to suggest a similarity of chemical form more than similarity of function or position of the two elements. Management of crop residues for maximising and optimising the timing of release of different nutrients will need to take into account the placement of different plant types and parts, particle sizes distribution and pre-treatment of material to efficiently manage short- and long-term soil fertility to sustain crops, particularly on degraded soils. Significant nutrient release of potassium, sulphur and magnesium from crop residues can be achieved from surface placement, with the release of potassium and sulphur managed by modifying residue particle size through appropriate harvesting, ploughing or sowing implement selection. High nutrient uptake crops and plant parts –where they can be economically viable to grow or separated by the harvesting technique – are particularly valuable as sources of nutrients and soil organic matter.
43

Interactions between sea urchins and macroalgae in south-western Australia : testing general predictions in a local context

Vanderklift, Mathew Arie January 2002 (has links)
Generalist herbivores profoundly influence the biomass and species composition of macroalgae assemblages. In subtidal ecosystems of temperate latitudes, large invertebrates are usually the most influential herbivores. I tested the prediction that exclusion of invertebrate herbivores would lead to changes in the biomass and species composition of the macroalgae assemblages that are a prominent feature of the reefs in south-western Australia. The most abundant invertebrate herbivores were sea urchins (Heliocidaris erythrogramma, Phyllacanthus irregularis and Centrostephanus tenuispinus), and these occupied different trophic positions. Heliocidaris was present at virtually all reefs surveyed, and was particularly abundant in the Fremantle region. Analyses of stable isotopes and direct observations of gut contents revealed that it was almost exclusively herbivorous, and that it mainly ate foliose brown algae. In contrast, Phyllacanthus and Centrostephanus were omnivorous; while they consumed large proportions of algae, a substantial proportion of the diet of both species was animal tissue. Because Heliocidaris is a generalist herbivore that occurs at high densities, it could exert a large influence on the macroalgae assemblage. This prediction was tested by a series of press experiments. Contrary to the prediction, Heliocidaris exerted a very minor influence on the biomass, and no detectable influence on the species composition, of attached macroalgae. However, it exerted a major influence on the retention of drift macroalgae and seagrass by trapping and feeding on drift. It exerted a particularly strong influence on retention of the kelp Ecklonia radiata. This kelp was not abundant in the attached algae assemblage (when all plots were pooled it ranked 35th in biomass), but was abundant as drift (ranking 1st). Most of the drift Ecklonia was retained by sea urchins, rather than freely drifting.Herbivorous fish may also influence macroalgae assemblages. To compare the effects of sea urchins versus fish on recruiting and adult macroalgae a 13-month exclusion experiment was conducted. There were no detectable effects of sea urchins (mainly Heliocidaris) on either recruiting or adult macroalgae. There were some patterns in the biomass of recruiting algae consistent with an influence by herbivorous fish; however, these patterns were also consistent with the presence of artefacts (shading and reduced water flow) by fish exclusion devices. I began with the prediction that large invertebrate herbivores were a major influence on the macroalgae assemblages of subtidal reefs in south-western Australia. Overall, there was little evidence to support this prediction: within spatial extents of tens of square metres and over periods of 1-2 years, only minor effects were detected. However, it remains plausible that herbivores exert an influence over long time periods across large spatial extents in south-western Australia. I propose that trophic subsidies support the comparatively high densities of Heliocidaris that exist at some reefs. I further propose that these subsidies mediate the effects of sea urchins on the attached macroalgae assemblage, and that they might play an important role in energy and nutrient cycling in these nearshore ecosystems.
44

Ecology of Eucalyptus victrix in grassland in the floodplain of the Fortescue River.

Florentine, Singarayer K. January 1999 (has links)
The WA coolibah tree, Eucalyptus victrix L. Johnson & K. Hill forms an unique and pristine woodland in the Fortescue Valley, in the Pilbara district of Western Australia. Until recently, no research had been done on E. victrix ecology and concern had been expressed by pastoral managers and others about the condition of the woodland occupied by this species. This research was an attempt to understand the ecology of coolibah using a multi-disciplinary approach.A population demographic study of stands in E. victrix woodland reveals that the present tree populations occupy larger areas than saplings and seedlings. Soil moisture and warm summer temperatures are believed to be stimulating factors for seedling recruitment of E. victrix. Different size classes (height/diameter) reflect different recruitment events and these reflect past availability of seeds and adequate soil moisture in that particular area of the woodland. Occasional grasshopper outbreaks and drought cause canopy shrinkage. Presence of hollow boles, restrict dendrochronological examination of tree ages.An important population study was of a post-seedling cohort at Roy Hill, where height distribution reflected a typical single recruitment event. In subsequent years (1995 - 1998) height measurement showed several peaks, suggesting that seedlings were now growing at different rates. Uniform and steady height growth was observed on saplings found at the edges of gilgai. During May 1998 several saplings flowered, it was assumed that E. victrix attained its reproductive maturity at mean height of 2.50 m and with a stem diameter of 50 mm.Seedling recruitment and subsequent growth mainly depend on heavy rainfall flooding events. Seedling recruitment occurs only from current seed rain. Seed longevity reduces after 54 days of burial at 50 mm depth. Mortality (4 - 6 leaf stage) of newly recruited seedlings during ++ / subsequent dry months is very high. Furthermore, allelopathic effects (root competition from established grass and insect herbivory) are additional causes of seedling mortality in the years of recruitment.Seedlings recruited at a burnt (disturbed) site, grew faster compared with undisturbed sites with less mortality. This suggested that fire created a suitable condition by reducing root competition, increasing soil nutrients and also creating a gap which providing sufficient solar radiation for seedlings to establish and develop into a healthy population. It is suggested that once newly recruited seedlings overcome the first summer, mortality rates during subsequent years are drastically reduced.Long-term waterlogging of E. victrix seedlings significantly increases seedling stem diameter. Large numbers of adventitious roots are developed and lenticels proliferate on the submerged portion of the stem. Flooding reduces each photosynthesis, transpiration and stomatal conductance. Flooding does not increase shoot fresh or dry weight on 4-, 8- or 17- week old seedlings. Leaf emergence may be stimulated on flooded seedlings compared with unflooded seedlings. While root dry weight is greater in 17-week old flooded plants than 13 - week seedlings, this difference is not significant. It is suggested that maintenance of a high root/shoot ratio is a drought adaptation. Furthermore, comparative study of flood tolerance in semi-arid eucalypt species suggests that those species intolerant of flooding seldom express morphological adaptations and fail to recover from physiological damage.The annual grass Setaria dielsii occurs under the canopy of mature E.victrix trees of the coolibah woodland. This species has probably displaced more palatable perennial grasses. Soil moisture under trees is slightly higher and soil temperatures are less extreme than away from the canopy. Growth of ++ / S. dielsii appears to be more associated with soil nutrient status. Levels of total N, Mg, K, and of electrical conductivity (EC) under trees are significantly higher than those away from the tree. Levels of Ca, Na, Fe, and organic carbon do not differ. The under story sub-shrub Malvastrum americanum is an important competitor with S. dielsii. Light availability may determine relative biomass contributions of the two species.The effect of the density of grass species, growing space and time of establishment on E. victrix seedlings (inter-specific competition), and the effect of density and growing space within E. victrix seedling populations (intra-specific competition) were studied under controlled conditions. Results indicate resources necessary for growth of individual E. victrix seedlings were more limiting under increase density of neighbouring grass species than under intra-specific competition. In particular photosynthetic area was drastically reduced in mixed culture.Lack of ground cover beneath the canopy of isolated E. victrix trees was ascribed to toxic or phenolic substances present in leaf, bark and leaf litter of E. victrix. Lactuca sativa seed germination subjected to extracts and leachate demonstrate that the fresh leaf of E. victrix possesses toxic substances which cause deleterious effects on both germination and radicle development. Similarly, increasing concentrations of leaf and bark leachate show reduced germination percentage of L. sativa seeds. Shoot and root biomass of grass and eucalyptus treated with leaf leachate were reduced. E. victrix leaf leachate significantly reduced shoot and root biomass of its own seedlings. High Performance Liquid Chromatogram (HPLC) analysis separated 11 and 8 possible toxic substances from leaf and bark extract respectively.
45

Nursing practice in a remote area : an ethnographic study.

Cramer, Jennifer H. January 1998 (has links)
The solitary position of nurses who practise in geographically isolated communities to provide direct health care to a predominantly Aboriginal population characterises nursing in remote areas. Munoz & Mann (1982) described this practice as unique. The uniqueness of this practice, however, has remained shrouded in superficial descriptions featuring service delivery at a one or two-nurse-post, the physical distance of nursing posts from hospital facilities and the autonomy with which nursing is performed. Only glimpses of the reality of nursing practice in a remote area have been revealed through the study of the educational needs of remote area nurses (Munoz & Mann 1982, Cameron-Traub 1987, Philp 1988, Kreger 1991a, Bell, Chang & Daly 1995). A key problem is the lack of a systematic description and detailed analysis of nursing as it is practised in a remote area.The purpose of this study was to explore, describe and analyse nursing practice in a remote area. The research was undertaken at Warburton, an isolated community mainly inhabited by the Ngaanyatjarra people in the Central Desert of Western Australia. An ethnographic design was chosen for this exploratory inquiry into the social and cultural pattern of everyday nursing practice. In a pre-entry study a suitable setting and informants were found. Fieldwork was conducted at the Warburton nursing post by the researcher and involved living on site for a year. Data gathering techniques were participant observation together with interviewing, collection of pertinent documents and the daily chronological recording of fieldnotes, memos and a personal journal. Data analysis was performed concurrently with data gathering. The process followed the Developmental Research Sequence Method by Spradley (1980). Through a cyclical process of data collection and analysis the domains, taxonomies and componential variables in the ++ / culture of remote area nursing practice emerged.Amorphous practice was the overall theme revealed in the underlying cultural patterns that shaped the practice of nursing in the remote area. The term amorphous practice is defined as the changeable nature of practice from nurse to nurse, from situation to situation, from time to time. This was observed in the recurrent differences between nurses in their knowledge, abilities and attitudes as well as in the variability between nurses in their management of client care. Contributors to the phenomenon of amorphous practice were found in three distinct, but inter-related, tributary themes termed detachment, diffusion and beyond the nursing domain. Detachment explained the nurses' feelings of separateness from the usual professional and organisational structures needed for the enactment of nursing. Diffusion encapsulated the broad spread of the nurses' role in remote area practice. Beyond the nursing domain described an unregulated practice considered to be outside the responsibilities of nursing care. The substantive theory of amorphous practice provided a detailed description of how nursing was practised in the remote area. It also explained why it was so different from nursing as it is generally understood by the profession.
46

An exploratory study of exhibitionism amongst adult men in Perth: a qualitative perspective as a guide for treatment

Maule, Linda J. January 2000 (has links)
The aim of this research is to talk to a sample of exhibitionists who are currently under the supervision of the Ministry of Justice (MOJ) in Perth, Western Australia in order to ascertain whether current treatment approaches used within the MOJ are the most effective and appropriate for this group of sex offenders. It was considered that the most effective research method would be a qualitative approach in order to gain insight into the offender's understanding of their offending behaviour and to attempt to identify their areas of treatment need. Through personal observations in working with exhibitionists and supported by the literature, an interview schedule was developed to combine a detailed social history with questions on communication, childhood issues, father issues and stress. Twenty voluntary participants were interviewed, having been accessed through the correctional community and prison environments. The objectives were (1) To identify any categories of exhibitionists and therefore better utilise treatment resources, (2) To identify the role of stress and communication deficits in offending behaviour of exhibitionists, (3) To determine whether exhibitionists would be more effectively treated within their own discrete population or with other types of sex offenders and (4) To identify a more appropriate treatment model. Another area of interest which was not specifically focussed on was whether findings would emerge which could predict which exhibitionists would progress to more serious sexual offending.The study found 3 categories of exhibitionist (1) Adolescent Onset Career Exhibitionists, (2) Adult Onset Career Exhibitionists and (3) Situational Response Exhibitionists. Whilst the first 2 categories contained participants whose offending was entrenched once commenced, either in early adolescence or adulthood, the latter group appeared to offend as a ++ / specific response to a life crisis. Further, findings indicated that there were 3 levels of communication deficits ranging from poor communication (65% of participants) to an inability to express negatively perceived emotions such as sadness or fear. All but one participant experienced high levels of stress and had difficulty coping with their symptoms. Again, all but one participant expressed unsatisfactory relationships with their fathers ranging from abandonment to emotional distance and 50% of the participants experienced physical, sexual and/or emotional abuse.A model of treatment was recommended which allowed for increased flexibility, allowing resources to be focussed on those offenders with the highest need. Further recommendations included increased liaison with the courts and Community Corrections in order to facilitate a more integrated approach to the client. It was also considered that exhibitionists should continue working within groups which contained other types of sex offenders.
47

The phenomenon of patient participation in their nursing care : a grounded theory study.

Henderson, Saraswathy January 1998 (has links)
In recent times there has been an emphasis on patients participating in their own nursing care. Studies have demonstrated that when patients participate in their own care, they experience positive outcomes, such as greater satisfaction with care, a sense of control, decreased vulnerability, and being effectively prepared for discharge. Practising nurses are of the view that patients should be involved in the planning, implementation, and evaluation of care in keeping with nursing's philosophy of provide holistic or patient-centred care. Despite this there is literature to show that nurses' espoused pro-participatory attitudes were not always enacted in the practice setting. There was a paucity of research to explain why this situation existed. Therefore, the purpose of this grounded theory study was to explore, describe, and analyse nurses' and patients' perspectives on the phenomenon of patient participation within the context of hospital nursing practice in Western Australia.Data were collected through formal and informal interviews with nurses, patients, non nurses, a doctor and relatives, focus group interview with nurses, participant observation, listening to nurses' handovers, examination of nurses' notes, and published literature. Thirty three Registered Nurses and 32 patients from medical, surgical, and extended care wards were formally interviewed. Additionally, 28 nurses and 17 patients were informally interviewed during participant observation. The total hours of participant observation was 142. The constant comparative method was used to analyse the data.The findings revealed that the basic social problem that faced nurses and patients was incongruence in their understandings of the meaning of patient participation and in their philosophies about nursing care. This had led to nurses and patients adopting three styles of participation, that is, ++ / participation inclusion which involved patients participating in all aspects of their care, including making decisions about their treatments, participation marginalisation which encompassed patients participating only in their daily living activities and pain management, and participation preclusion which involved patients not participating in any aspects of their care. This resulted in nurses and patients coming together with their own different styles of patient participation, which caused conflict in viewpoints about how care should be provided and received at the bedside. Exacerbating the problem of incongruence were the hospital contextual conditions of economic constraints, management structures, presence of technology, and culture of medical dominance. These contextual conditions also modified the process that nurses and patients used to deal with the problem.The basic social process that nurses and patients used to deal with the problem of incongruence was labelled accommodating the incongruence and involved three phases. It was found that varying intervening conditions that affected the nurses, patients, or both, and the day-to-day ward environment modified this process. The first phase, which was labelled coming to terms with the incongruence, involved nurses and patients encountering and acknowledging that there was an incongruence. The second phase, which was termed rationalising the incongruence, involved nurses and patients observing and assessing each other's behaviours. The third phase, which was labelled seeking resolution: minimising the incongruence, involved nurses and patients adjusting their behaviours so as to achieve some balance. This third phase was nurse-driven with patients playing a subsidiary role. This was considered to be due to nurses being at their optimum physical level of functioning and in their own socio-cultural work ++ / environment as opposed to patients who were ill and therefore vulnerable. Nurses adjusted their behaviours, depending on the patients' preferred style of participation, by either increasing patients' control and level of participation, as well as increasing their own level of control, to upgrade patients' input; or decreasing patients' control and level of participation and decreasing their own level of control to downgrade patients' input; or alternatively converging patients' control and level of participation to meet with their own style of participation, without them increasing of decreasing their own control. Through converging, the nurses were able to upgrade or downgrade patients' input. From this nurse-patient interactive process, which was dynamic and reciprocal, a theory of patient participation emerged. This was labelled Accommodating Incongruity. Implications for nursing practice, management, theory, education, research, and consumerism are discussed and directions for future research are provided.
48

The culture and improvement of Western Australian senior secondary schools.

Cavanagh, Robert F. January 1997 (has links)
The operation and development of Western Australian senior secondary schools is based upon traditional theories of organisational management and school administration. The study sought to explore alternative conceptions of the nature of schools and the processes by which they can be improved.Examination of research on school effectiveness revealed that student learning outcomes were consequential on the values and norms of the staff of schools. These values and norms constitute the culture of a school and govern the professional activity of teachers. School culture can be contrasted with the formal school organisation in which the work of teachers is prescribed by explicit rules and regulations. Viewing schools from a cultural rather than organisational perspective requires conceptualising the school as a learning community. A learning community is bonded together by common expectations about the roles of teachers and the learning of students. The predominant consideration is the educative mission of the school and not the requirements of the formal organisation. Organisational development is viewed as cultural transformation. The improvement of the school is facilitated by the growth of a school culture which is supportive of the professional needs of teachers and the educative needs of students.The study utilised a developmental mixed-method research approach to investigate the nature, temporal stability and improvement of the culture of local senior secondary schools.A quantitative instrument was developed to measure aspects of school culture identified in the school effectiveness literature. The School Cultural Elements Questionnaire (SCEQ) provided a measure of the level of teacher efficacy, emphasis on learning, collegiality, collaboration, shared planning and transformational leadership in local schools. The SCEQ data were supplemented by data from a ++ / stratified sample interview programme in two schools. Empirical findings indicated school culture was internally dynamic, in interaction with its external environment and capable of changing. Interview data provided examples of internal and external influences on the maintenance, growth and decline of school culture.The results of the empirical phases of the study were applied in the development of a model of school culture, the School Improvement Model of School Culture. The model contained six cultural constructs which are characteristic of school culture and the processes by which it can be transformed. The model was then applied in a detailed examination of practical and theoretical aspects of Western Australian systemic school improvement initiatives. The effectiveness of these initiatives was explained as a consequence of implementation strategies and their interaction with the prevailing school culture.The study is important for school level personnel, school improvement programme designers and educational researchers. In particular, the School Improvement Model of School Culture provides a significant alternative conception of the nature of schools and the processes by which they improve.
49

Cryopreservation of somatic germplasm of selected Australian monocotyledonous taxa (Haemodoraceae).

Turner, Shane January 2001 (has links)
The South West Botanical Province of Western Australia is one of the most floristically rich areas of the world with over, 8,000 species present, the majority of which (70%), are endemic to this region. Coupled with this high level of endemism, many taxa are threatened which makes them vulnerable to habitat alterations, modifications and destruction. Significant habitat alteration in many areas has resulted in 27 species becoming extinct in the South West Botanical Province, while an additional 327 species are classified as rare and endangered. In the context of stemming this loss of biodiversity, research in cryopreservation was undertaken to provide offsite protection and conservation of somatic germplasm.Cryostorage techniques were evaluated in this study to determine the key factors which may affect the ability of somatic tissues of Haemodoraceae species to survive, recover and grow following liquid nitrogen (LN) immersion and storage. Using Anigozanthos viridis as a comparator in most experiments, the base vitrification protocol was established, which involved: (1) preculturing shoot apices on 0.4 M sorbitol for 48 h; (2) incubation in a vitrification cryoprotective solution (PVS2) for 25 min at 0 degrees celsius; (3) LN immersion; (4) recovery to active growth through warming (immersion in a 40 degrees celsius water bath). Using this procedure the highest post-LN survival of shoot apices for A. viridis was 41.4 plus or minus 6.1% Four additional taxa were successfully cryopreserved with this base protocol (Anigozanthos manglesii, A. rufus, Conostylis wonganensis and A. rufus x A. pulcherrimus); a fifth taxon, Macropidia fuliginosa, however, proved unresponsive.To improve on post-LN survival, further research established that four of the six study taxa responded to the following amendments to the basic protocol: (1) longer preculture duration; (2) preculture on ++ / 0.8 M glycerol rather than sorbitol, (3) utilisation of PVS2 solutions with reduced DMSO content; and (4) incorporation of an additional loading phase (2 M glycerol plus 0.4 M sucrose for 20 mins at 0 degrees celsius).Macropidia fuliginosa, a species with poor recovery after LN exposure, was successfully cryostored using somatic embryos. Treatments which resulted in the highest survival (67.3% 5.7 plus or minus %) included preculture with 0.4 M sorbitol, and incubation in PVS2 for 30 min. Further experimentation indicated that preculture for two days on 0.8 M glycerol (replacing 0.4 M sorbitol) was more beneficial for achieving high post-LN survival.Post-LN survival was significantly correlated to the use of polyalcohols when the total number of hydroxyl (-OH) groups (regardless of molarity) present was the same as that found in 0.4 M sorbitol. It was hypothesised that hydroxyl number is more important than molarity in membrane stabilisation, during dehydration and cooling. Post-LN survival was also found to be significantly influenced by stereochemical arrangement of the -OH groups of polyalcohol molecules used in the preculture media. Finally, post-LN survival was also found to be significantly influenced by the size of the molecule, with smaller polyalcohols with more -OH groups on one flank of the carbon chain being superior as cryoprotective agents.The influence of plant growth regulators on post-LN survival and recovery growth was also investigated. The survival of shoot apices was not correlated to cytokinin or auxin treatments administered in culture media prior to cryostorage. However, in the recovery medium, a combination of cytokinin and 0.5 mu M GA(subscript)3 in the medium was found to be the most efficacious for obtaining healthy plantlets.Genetic fidelity was then examined using Amplified Fragment Length Polymorphism (AFLP). Plantlets of one done kept ++ / or maintained under the following conditions: (1) standard tissue culture conditions; (2) cold storage and (3) cryostorage, over a 12 month duration, showed no detectable genetic changes.Further, shoot apex viability evaluated at regular intervals (after 0, 3, 6 and 12 months of LN storage) suggested that medium term storage of samples cryopreservation did not reduce shoot apex viability over this time span.This study has provided a better understanding of the factors influencing post-LN survival and recovery and, as a result, the cryopreservation protocols have been refined. Consequently, the prospects for conserving threatened Haemodoraceae species from Western Australia through cryostorage is now significantly improved.
50

The phytoplankton ecology of Wilson Inlet, Western Australia.

Twomey, Luke J. January 2000 (has links)
This thesis examines the phytoplankton ecology of Wilson Inlet, Western Australia with relation to the changing physical, chemical and biological environment.

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