Veterinary Science Collected Works - Theses
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ItemThe effect of Bonzi (Paclobutrazol) on height and flowering of the paper daisies Rhodanthe chlorocephala subsp.rosea and Rhodanthe manglesii( 1994)The pink paper daisies Rhodanthe chlorocephala subsp.rosea and Rhodanthe manglesii are Western Australian wild flowers bush harvested as cut flowers. They produce numbers of showy, long lasting inflorescences at the tips of 50 to 60cm tall stems in spring. The growth retardant Bonzi(R) (paclobutrazol) was applied to both species as soil drenches or whole plant sprays alone or combined seed soaks and drenches. The retardant was applied at various concentrations and times, to determine if plant height could be reduced for pot plant production. Growth was measured weekly and recorded on a graph of maximum/TinimuT desired height (20-30cm). After initial treatments on week 4, all treatments were applied using Graphical Tracking techniques, that is, when actual growth deviated above the maximum height line. Plant height was suppressed with all applications of Bonzi(R) (paclobutrazol). Increasing both the rate and number of applications of BonznK)(pac1obutrazo1) led to an increase in shoot suppression, flowering time and number. The combined seed soak (400ppm Bonzi(R)) and multiple drench application (Bonzi(R) 4mg ai/pot x 3) was most effective in suppressing shoot elongation of R.chlorocephala subsp.rosea with plants 41% shorter than untreated plants. lowering was delayed and numbers reduced, but the compact plants had sufficient numbers of flowers at the end of the trial period to appeal to consumers. Bonzi(R) caused very noticeable delays in flowering in all treated Rhodanthe manglesii plants. The 4mg drenches, (4mg ai/pot x 3) gave the most satisfactory result producing plants 38% shorter than untreated controls but some pots had not flowered by the termination of the trial. The best results, in respect to height, were again the combination seed soak plus drench, with only a single 4mg drench application required to reduce height by 48%, but germination was suppressed excessively and flowering was unacceptably delayed. Although growth was suppressed significantly by whole plant sprays none were saleable due to the unsightly chlorotic foliage effects on both species.
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ItemTaylors Creek revegetation analysis of plant establishment( 1988)Plant survival data was collected from parts of the Taylors Creek revegetation site approximately eighteen months post planting to determine the overall percentage survival rate of all species in the sample and the percentage survival rate of each species in the sample. This data is used to consider the efficacy of rationale and technique employed in the revegetation of Taylors Creek during 1986. Data was collected by a field survey of a randomly selected sample of planting areas comprising 12 percent of the total planting. Total percentage survival of the sample was 46 percent and the survival of each species ranged from 0 to 100 percent with a survival rate of 58 percent for the group of species best represented in the sample.
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ItemConservation analysis of Burnley Gardens( 1994)V.C.A.H Burnley is a horticultural college surrounded by a historic landscape. The gardens were first established by the Horticultural Society of Victoria in 1863 for the acclimatisation of exotic plants especially fruit trees and in 1891 it became a School of Horticulture. A Significant Tree Study and Tree Census provides a current record of the vegetation and its condition. Through a series of maps and verbal descriptions the study depicts the changes that have occurred in the gardens from the 1860s to the present culminating in a Statement of Significance. To ensure the historical integrity of the gardens remains intact, a conservation policy has been formulated which has guided the development of the management recommendations.
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ItemSome calculations of potential photosynthetic yield( 1979)Detailed calculations of light relations and seasonal potential photosynthesis are carried out for models of leaf canopies of closed trellis orchard design, with the object of comparing the effectiveness of light capture and usage in canopies of various fork angles and various values of leaf area index. It is assumed that all canopies have adequate water, carbon dioxide and nutrients, a condition satisfied in practical orchards. After examination of a very simple model, a detailed model is set up to take full account of direct sunlight, diffuse skylight and light scattered diffusely by foliage. Irradiance at leaf surfaces of various orientations is calculated from first principles, since in a canopy whose geometry is not independent of azimuth there is no straightforward way of assessing diffuse irradiance. An analytical expression is derived for rate of photosynthesis averaged over sunlit leaves randomly oriented in azimuth at any given isotropic diffuse irradiance. The calculated field of photosynthetically active radiation is used to estimate canopy net photosynthesis during the fruit-filling season for peach orchards. In such canopies the foliage-scattered diffuse light is found to make a relatively small contribution (about 10 percent) to net canopy photosynthesis. It is found that for any given value of leaf area index the seasonal potential photosynthesis, whether net or gross, increases as canopy fork angle increases, in the range of angles from 40 degrees to 180 degrees. The estimated absolute harvest yield of peaches in a 60 degree canopy is found to be lower than the mean value of published measured yields by about one standard deviation. Reasons for this are discussed. The low estimated yield does not affect the validity of theoretical comparison between the various canopies. One of several possible causes of an underestimate of potential photosynthesis is neglect of penumbral effects. A theoretical framework is developed for estimation of the error introduced in photosynthesis calculations by the assumption that incident direct solar radiation is a perfectly parallel beam of light. The calculations of Miller and Norman (1971) on distribution of direct sunlight flux density along transects in sunflecks are discussed. The present theory is developed in terms of probabilities of irradiation by full sun and by partially shaded sun and the probability of umbra at any level in a leaf canopy. Analytical expressions are derived for probability density with respect to fraction of the full sun radiant flux density for partial shading by a straight edge, a circular disk, and a thin strip. It is shown that solar limb darkening may be neglected for the present purpose. The geometry of umbra and penumbra due to crossed shading edges is discussed and quantified. The developed theory is applied to hypothetical canopies of randomly dispersed horizontal circular leaves and to randomly oriented and dispersed vertical leaves. A parameter called the characteristic leaf area index is introduced; this parameter, which includes foliage density and leaf dimensions, may be used in assessing the error in estimated canopy photosynthesis due to neglect of penumbra. Application of the theory to the effects of vertical distribution of foliage on canopy photosynthesis is briefly discussed. The underestimate of potential canopy photosynthesis in a peach tree canopy due to neglect of penumbra is found to be of order 5 percent.