School of Agriculture, Food and Ecosystem Sciences - Theses

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    Observations on fomes pomaceus (pers.) big. & guill. infecting plum trees ; An investigation of sooty moulds with particular reference to their taxonomy and their growth in culture
    Fisher, Eileen. (University of Melbourne, 1974)
    I. The Taxonomy of "Sooty Mould "-Fungi. 1. Existing schemes of classification are discussed. 2. A classification is offered in which, the inaccuracies of other taxonomic schemas, are corrected. 3. "Sooty Moulds� are arranged, according to the macroscopic appearance of their growth, into four groups. 4. Diagnostic features are given for five families of ��sooty mould"-genera. 5. The families Capnodiaceae v. Hohn. and Chaetothyriaceae Th. are emended. A key to the identification of the genera Included in each of these families Is given. 6. Chaetothyrium Citri (Arn.) nov. comb. is recorded for the first time in Australia. 7. A new species, Phycopsis australiensis is described. II. An Instigation of the Cultural Behaviour of some "Sooty Mould" Fungi with reference to Climatic Conditions. 1. Eight species which, were isolated from epiphytic moulds, are included in this study. 2. A preliminary survey is made of the nutritional recuirementa of these species. 3. The methods used for recording measurements of colony-size and for calculating the rate of growth are described. 4. Measurement is made of the growth occurring at the following temperatures: 10�C., 15�C., 18�C., 20�C. and 25�C. The optimum growth temperatures determined for seven "sooty mould" endemics lie between 15�C and 20�C. 5. The methods which were adopted for growing these fungi under conditions of controlled atmospheric humidity are described. 6. The humidity growth-rate relations determined here are similar to those of fungi from quite unrelated habitats. 7. The geographic distribution of epiphytic "sooty moulds" is discussed in relation to the temperature and humidity requirements of the species examined here. The temperature-growth relations of the Capnodiaceae species do not confirm the assumption that high temperatures are favourable, rather It would appear that growth is active during the winter months. 8. It la suggested that the deciduous nature of the flora in cool temperate regions is responsible for the almost entire absence of the Capnodiaceae in these regions.
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    Wettability, surface tension and venturi scrubber performance
    Atkinson, David Scott Forman. (University of Melbourne, 1973)
    The addition of a wetting agent or detergent to the liquor of both model and industrial venturi scrubbers, markedly improves particulate collection efficiency. A study of the literature Indicated that an explanation for the improvement was not available. However, it would appear that the role of the wetting agent is to reduce surface tension which could either reduce the drop size or increase the drop-particle attachment or both. A reduction in drop size would improve efficiency if either the impaction or diffusion mechanism of aerodynamic collection was operating. A number of empirical equations have been developed to correlate the operating parameters of an air-liquid atomizer with the drop size distribution generated. These equations differ as to the role of surface tension and there has been only one detailed experimental study under conditions similar to those in a venturi scrubber. Changes in surface tension of water have not been studied as a single variable and it was decided to do this in a model venturi scrubber. The venturi was operated so that drops rather than clouds (composed of ultra-fine drops) were generated. The break-up of the liquid jet and the drops were photographed. The drop size distribtuions for water and water solutions of an ionic and non-ionic detergent giving minimum surface tensions were obtained. There was no statistical significance in the difference between the means of the three distributions and indeed little difference between the shape of the curves. It is concluded that reduction in surface tension of water on addition of a detergent does not influence the drop size distribution in a venturi scrubber. This is thought to be due to the fact that a detergent will only reduce the surface tension of water at the water surface. The inter-molecular attraction within the bulk of the water is not changed on addition of detergent. Thus, when a water jet is rapidly atomized the detergent has insufficient time to spread to or over the newly created surfaces. At the moment of atomization, the surface tension of the solution of detergent in water is effectively that of water alone and hence the drop size is not altered. Addition of detergent does improve venturi scrubber performance and it could do so by increasing the attachment of particles to drops. Alternatively, the bubbles which are formed only after the addition of detergent, may collapse into very fine drops which could act as highly effective collectors for sub-micron particles. Agreement between the median drop diameters obtained in this work and those predicted from the empirical equation of Ingebo and Foster was satisfactory.
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    The uptake and distribution of nitrogen by two wheat varieties and their growth response to soil nitrogen
    Dalling, Michael J. (University of Melbourne, 1971)
    In many areas of the world human hunger prevails as a result of a shortage of food. Malnutrition due to low-quality diet is even more common, occurring in many areas where food supplies are adequate to meet caloric requirements. A common cause of malnutrition is shortage of high quality protein. Since wheat and other cereals provide one-half of the world's calories and one-third of the world's protein, any increase in the productivity of these crops may have far-reaching importance. Throughout the world there is an increasing use of nitrogen fertilizers in an attempt to increase grain yield and grain protein. However, in the major grain-growing regions of Australia the benefits obtained from nitrogen fertilizers have been small. While the present practice of having clover-ley pastures as an integral part of the rotation persists, and while the presently available wheat varieties continue to be used, it is doubtful whether nitrogen fertilization will be of any wide-spread value in Australia. However, because of the recently introduced restrictions on farm output of wheat, it is likely that emphasis will be placed on maximizing yield per acre in order to devote the maximum portion of the farm acreage to other enterprises. This may cause a change in farm rotations and result in a more intensive use of smaller areas. In this situation supplemental nitrogen may well be of value. The overall objective of this study was to relate the growth of the wheat crop to the level of mineral nitrogen (nitrate-N and ammonium-N) in the soil throughout the season. The soil nitrogen was varied by applying fertilizer nitrogen at both different rates and different times. Also different varieties were used because there is an accumulating body of evidence that some aspects of nitrogen assimilation by plants are under genetic control and can therefore be manipulated by the plant breeder (Hageman, Leng and Dudley, 1967; Beevers and Hageman,1969). The capacity of the plant to take up nitrogen from the soil and to use it efficiently and eventually deposit it in the grain is an important determinant of grain yield and grain protein. These aspects have received special attention in the present study.
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    An ecological comparison of California red scale (Aonidiella aurantii (Mask.)) and yellow scale (Aonidiella citrina Coq.) on citrus
    McLaren, Ian William. (University of Melbourne, 1970)
    Red scale (Aonidiella aurantii (Maskell)) and yellow scale (Aonidiella citrina Coquillet ) have been compared by constructing age-specific life and fecundity tables over a range of temperatures and humidities. Using; the data from these tables the values were calculated for rm The Intrinsic Rate of Natural Increase, rc The Capacity for Increase, Ro The Nett Reproductive Rate, and LAMBDA The Finite Rate of Increase. A study of these parameters showed that: (1) The upper thermal deathpoint was similar for both species. (2) A. citrina multiplied more rapidly than A. aurantii over the median range of temperatures. (3) The threshold of population growth was about 13�C for A. aurantii and 18�C for A. citrina. A study was made of the settling behaviour of crawlers on leaves, and it was found that: (1) Crawlers of A. aurantii were negatively geotropic, and because of this they tended to settle on the upper tissues of the host plant. (2) Crawlers of A. citrina demonstrated negative phototaxis, and as a result they tended to settle on the shaded undersurface of leaves. Correlations were found between the fecundity of red scale females on leaves, and: (1) Size of the adult (+ve). (2) Increase in size from 2nd instar to adult (+ve). (3) Initial natality (+ve). (4) The feeding site w.r.t. distance from vascular tissue in the leaf (-ve). A further correlation (+ve) was found between delayed mating and initial natality. This was thought to result from continued ovulation in the unfertilized female, a postulate which was verified by examining the intreabdominal eggs in virgin females of various ages. These results have been used to discuss the relative abundance and distribution of both scale species in Sunraysia, the dispersai and invasiveness of each species, and the present limitations on biological control of red scale. On the basis of this project it has been possible to formulate a revised approach for regulating red scale populations in Sunraysia.
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