School of Agriculture, Food and Ecosystem Sciences - Theses
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ItemNo Preview AvailableThe soil-root interface of Lupinus Albus L. and its significance in the uptake of manganese, iron, and phosphorus(University of Melbourne, 1981)It has been demonstrated using an agar film technique that L.albus is able to dissolve colloids of iron/silicate, iron/ phosphate, aluminium/silicate and aluminium/phosphate and also suspensions of manganese dioxide, calcium mono-hydrogen phosphate and ferric hydroxide. Dissolution of these compounds was most marked in proteoid root regions of lateral roots (dense clusters of 20 laterals of limited growth) and certain regions of the tap root. Soil associated with these root regions was found to contain more protons, reductants and chelating agents than the bulk soil. The effect of iron and phosphorus nutrition was examined in acid washed sand. The effect of phosphorus nutrition was also examined in three soils (acid, neutral and alkaline) under glasshouse conditions. The response of wheat, L.angustifolius and L.albus to phosphorus was compared at three sites (acid, neutral and alkaline) in field trials. Proteoid root formation was found to be predominantly controlled by the phosphorus status of the plant. Manganese uptake in L.albus was related to proteoid root formation, and inversely related to phosphorus supply in both L.albus and L.anqustifolius. The ability of L.albus to utilise soil and added phosphorus decreased as the pH of the soil increased. The role of micro-organisms in proteoid root formation and function was investigated. Proteoid roots formed under sterile conditions, but more formed under non-sterile conditions. The effect of varying root morphology on exudation characteristics in the rhizosphere was examined by computer simulation. The main exudate from the roots of L.albus has been identified by gas-liquid chromatography and mass spectrometry as citric acid. It is hypothesised that citrate ions react with the soil colloid and form a diffusible polymeric ferric hydroxy phosphate which moves to the root surface where it is broken up by a combination of ferrous ion uptake, proton secretion and reduction. An attempt has been made to examine iron in the roots using electronmicroscopy and X-ray microprobe. The results suggest that iron is mobilised about the root system in large amounts, although this is not reflected in above ground parts. The effect of intercropping wheat and L.albus was examined in both glasshouse and field for effects on the mineral nutrition of both species. Wheat intercropped with lupins appears to have access to a larger pool of available phosphorus, manganese and nitrogen than has wheat grown on its own.
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ItemNo Preview AvailableSoil-plant relationships : with particular reference to soil physical properties and root growth(University of Melbourne, 1974)The candidate was admitted to the degrees of Bachelor of Agricultural Science (1948) and Master of Agricultural Science (1952) in the University of Melbourne. He was awarded the degree of Doctor of Philosophy (1958) by the University of Adelaide. The candidate is eligible, subject to approval of the Faculty of Agriculture, for candidature for the degree of Doctor of Agricultural Science. This thesis is submitted to the University of Melbourne towards the requirements for that degree. The experiments described in the thesis were conducted chiefly at the C.S.I.R.O Regional Pastoral Laboratory, Deniliquin, New South Wales (l950-54), and at the Waite Agricultural Research Institute, University of Adelaide (1955 onwards). During these periods, one year, 1952, was spent at Cornell University, Ithaca, New York, and another, 1961, at the Department of Soils and Plant Nutrition, University of California, Berkeley. Part of 1968 was spent at the Department of Botany, University of Edinburgh. The papers presented in the thesis deal with processes operating in soil-plant systems of agronomic interest. Although the work has not, for the most part, been immediately applied to agriculture by the candidate, it is hoped that it may lead to a better understanding of principles that affect soil management. The work is viewed as a contribution to the scientific study of the soil as a medium for the growth of crops. A short account of the general development of the work is followed by sections dealing with particular subjects. The following sequence is adopted for each subject: Firstly the relevant papers of the candidate are listed in chronological order. Secondly, the papers are discussed in relation to other published work. Finally, the candidate's papers are assembled, also in chronological order. References to papers mentioned in discussion are given at the end of the thesis.
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ItemSome factors affecting the availability of nutrients to plants( 1980)This thesis describes work done between 1954 and 1979 as an officer of CSIRO - initially at Armidale, New South Wales, then for one year on a CSIRO Studentship at Rothamsted Experimental Station, United Kingdom, and finally in Perth, Western Australia. Included in the thesis are papers which arose from these for a masters degree and from a Ph.D. These are identified and are included in a background section because they indicate some of the influences that gave rise to subsequent work. They are not submitted as evidence for a D.Agr. Sc. degree. The thesis begins with a section in which the general trends of the work are outlined. This is followed by a list of publications. In order to summarise the work, the papers have been allocated into ten groups. The groups then follow. A table of contents precedes each group. For those papers for which I was the single author, I was solely responsible for planning the research and writing the paper. Where joint authorship is involved, the rule I have followed is that the senior author had major responsibility for the work and for the paper. This statement is amplified with respect to some of the individual papers in the summary section. All the papers have been published or have been accepted for publication.