Bibliography: leaves 124-136. This thesis gives an overview of factors used in weed risk assessments and explores the disparity between the measured high accuracy rate of the weed risk assessment system (WRA) as implemented in Australia and the pessimistic assessments of some workers about the possibility of predicting the weed potential of plant species imported in the future. The accuracy of the WRA may not be as high as previously thought, and it varies with weed definition and taxonomic groups. Cluster analysis and comparative analysis by independent contrasts were employed to determine the value of individual biological and ecological questions on the WRA questionnaire. Results showed that some WRA questions could be deleted from the questionnaire and the scores for others weighted differently. The WRA is not a reliable predictor of weeds when it is considered in the context of the base-rate probability of an introduced plant becoming weedy in Australia. As a result a far greater number on non-weeds will be placed on the prohibited imported list than was initially expected.

Bibliography: leaves 125-141. / xiii, 141 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Addresses the poor control of major weed species under southern Australian winter conditions by the non-selective post-emergence herbicide, glufosinate in order to determine the best way to use it. Dose response experiments were performed under simulated southern Australian winter conditions, and demonstrated a variable glufosinate efficacy between Lollium rigidum and Avis sterilis. Glutamine synthetase assays showed that target site sensitivity did not influence these results. Spray retention experiments showed no influence from plant size or morphological features, while metabolic studies showed that only a small proportion of glufosinate was metabolised in both species. Tests of several populations of Raphanus raphanistrum showed that all populations, despite geographical origin, were poorly controlled by glufosinate, in both field and simulated conditions. Experiments conducted at higher temperatures showed enhanced glufosinate efficiency. Experiments with the use of co-herbicides, chelating agents, fertilizer salts and hormones were also carried out. Studies on the effect of the pH of the herbicide solution on cell uptake showed that uptake into the cell wall only was enhanced by reducing the buffer pH. Shows that the poor efficacy of glufosinate against these species is mainly due to poor translocation of the herbicide. / Thesis (Ph.D.)--University of Adelaide, Dept. of Applied and Molecular Ecology, 2003

Bibliography: leaves 125-141. / xiii, 141 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Addresses the poor control of major weed species under southern Australian winter conditions by the non-selective post-emergence herbicide, glufosinate in order to determine the best way to use it. Dose response experiments were performed under simulated southern Australian winter conditions, and demonstrated a variable glufosinate efficacy between Lollium rigidum and Avis sterilis. Glutamine synthetase assays showed that target site sensitivity did not influence these results. Spray retention experiments showed no influence from plant size or morphological features, while metabolic studies showed that only a small proportion of glufosinate was metabolised in both species. Tests of several populations of Raphanus raphanistrum showed that all populations, despite geographical origin, were poorly controlled by glufosinate, in both field and simulated conditions. Experiments conducted at higher temperatures showed enhanced glufosinate efficiency. Experiments with the use of co-herbicides, chelating agents, fertilizer salts and hormones were also carried out. Studies on the effect of the pH of the herbicide solution on cell uptake showed that uptake into the cell wall only was enhanced by reducing the buffer pH. Shows that the poor efficacy of glufosinate against these species is mainly due to poor translocation of the herbicide. / Thesis (Ph.D.)--University of Adelaide, Dept. of Applied and Molecular Ecology, 2003