I used a data-set of 986 plant species (from 493 genera in 195 families) obtained from a literature search and a new data collection for 58 tropical tree species (from 31 genera in 18 families) growing in two contrasting forest types in Brunei Darussalam: mixed dipterocarp forest on moderately infertile ultisols and fluvisols, and heath forest on acidic and nutrient-poor spodosols.  I provide statistical evidence for the existence of discreet groups of species representing Al accumulators and non-Al accumulator based on foliar Al concentrations.  The threshold foliar Al concentration was higher for tropical plants (range 2.3-3.9 mg Al g^-1) than temperate plant (1.1 mg Al g^-1). Species’ mean log foliar Al concentration was also higher for tropical (0.73 ± 1.11 mg Al g^-1) than temperate plants (0.16 ± 1.07 mg Al g^-1).  I used the tropical Al accumulating shrub <i>Melastoma malabathricum </i>L. as a study species to test the hypotheses that growth would be stimulated by Al addition.  Growth of <i>M. malabathricum </i>seedlings was stimulated by Al addition when the external supply of macronutrients was very low, and this growth response was associated with an increase in net assimilation rate and specific leaf area.  Foliar Al concentration was positively correlated with foliar concentrations of Ca and Mg across 16 Al accumulator species sampled in the field study in Brunei Darussalam, while foliar Al and K concentrations were correlated positively in <i>M. malabathricum </i>seedlings growing in the solution culture experiments.  These positive correlations contradict the hypothesis that Al inhibits the uptake of nutrient cations and they may contribute to the positive growth response to Al addition in Al accumulator plants.

Thesis (MTech (Food Technology))--Cape Peninsula University of Technology, 2018. / Fungal diseases in vineyards are one of the main causes leading to economic losses within the viticultural sector and are continuously increasing over years. The most common of these fungal diseases are powdery mildew, downy mildew and grey mould. Commercial fungicides to treat the above-mentioned diseases are available and their usage is regulated under Act 36 of 1947 to comply with Good Agricultural Practises (GAP). However, the application of less-harmful, natural alternative fungicides to control vineyard diseases are currently an important research focus since the demand for organic products by consumers and retail companies are increasing. However, fungicide residues can alter the fermentation process and prevent some biochemical pathways of yeast metabolism involved in phenolic and/or aroma compound production that are critical for sensory quality. Therefore the aim of the study was to investigate the effect of fungicide treatments on the fermentation rate, yeast proteins expressed, aroma compounds released and sensory profile of wines produced. In the study, Chenin Blanc grapes treated with chemical and natural fungicides (1x treatment and 2x treatment) under Good Agricultural Practises (GAP) were used to produce small-scale wines and laboratory-scale fermentations. Laboratory-scale fermentations were conducted in duplicate using the commercial Saccharomyces cerevisiae (S. cerevisiae) Active Dry Wine Yeast (ADWY) strains VIN 13 and VIN 7. The fermentations were monitored by frequently weighing until they stabilised (CO2 weight loss). Small-scale wines were produced using the commercial S. cerevisiae ADWY strain VIN 13 only. Wines were made according to the standard Nietvoorbij experimental winemaking procedure. At the end of fermentation, lees samples were plated onto Yeast Extract Peptone Dextrose (YPD) agar and colonies grown were subjected to CHEF gel electrophoresis to confirm that the S. cerevisiae yeast strain inoculated at the beginning of the fermentation completed it. Moreover, fermenting wine samples, collected at the start (lag phase) and at end of fermentation (stationary phase), were subjected to protein extraction, quantification and characterisation in order to investigate fermenting wine yeast proteins. Furthermore, the final wines were subjected to chemical analyses as well as measurement of aroma enhancing metabolites (esters, higher alcohols, fatty acids and thiol compounds) using GC – FID and MS. Additionally, duplicate samples of the wines were evaluated sensorially by a trained panel of 12 winemakers and researchers, using an unstructured line scale. Wines were compared to the control wine according to visual (colour), flavour (tree fruit, tropical fruit, and wine foreign), taste (body mouthfeel, acidity) and overall quality. The data collected from the study was statistically analysed using a two-way analyses of variance (ANOVAs) and subject to a multiple factor analysis (MFA). From the results obtained in the above study, it was concluded that yeast strains used for winemaking completed the fermentations at a similar rate to their respective controls. In addition, small-scale cellar fermentations showed that fungicide treatments (1x treatment and 2x treatment) compared to the controls had no notable negative effects on wine aroma and sensory profiles although differences were observed in the proteins expressed after the fermentation. Overall, the fungicide treatments did not negatively affect the yeast performance, yeast protein expressed, aroma compounds released and sensory profiles of the wines produced. Further studies are recommended on other white as well as red wine grape cultivars to fully assess the effects of the fungicides.

Orientador: Marcelo de Almeida Silva / Banca: Dirceu Maximino Fernandes / Banca: Paulo Alexandre Monteiro de Figueiredo / Resumo: Com a finalidade de melhorar a qualidade da matéria-prima da cana-de-açúcar é recomendado o uso de produtos químicos como maturadores, os quais podem acelerar o processo de maturação e inibir o florescimento. Com a busca de uma agricultura mais sustentável, ocorreu uma mudança na prática da colheita, passando de colheita com queima prévia da cana-de-açúcar para colheita sem queima. Devido a essa mudança, houve aumento nas quantidades de palha e de ponteiro da canade-açúcar deixadas na superfície do solo, as quais podem trazer benefícios para o ecossistema, destacando-se a reciclagem dos nutrientes. O presente trabalho teve por objetivo avaliar a aplicação de diferentes produtos químicos como maturadores e seus efeitos na composição nutricional em diferentes porções da parte aérea remanescentes da colheita. A variedade utilizada foi a RB966928, e o delineamento experimental utilizado foi o de blocos casualizados com quatro repetições. Os tratamentos foram constituídos de testemunha, dose de 0,5 L ha-1 de glifosato, 0,02 kg ha-1 de sulfometurom-metílico e 0,80 L ha-1 de trinexapaque-etílico. As amostras foram separadas em folha +1, copa foliar e ponteiro, sendo realizada a análise química para se determinar os teores dos nutrientes. As variáveis nutricionais foram avaliadas em função do tempo, aos 0, 15, 30, 45 e 60 dias após a aplicação dos tratamentos até a colheita. Tanto para os macro quanto para os micronutrientes o trinexapaque-etílico manteve o teor da maioria dos... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: In order to improve the quality of the raw material of sugarcane, it is recommended to use chemical products as ripeners, which can accelerate the ripeness process and inhibit flowering. With the search for a more sustainable agriculture, a change occurred in the practice of the harvest, passing from harvest with previous burning of the sugarcane to harvest without burning. Due to this change, there was an increase in the amount of sugarcane straw and pointer left on the soil surface, which can bring benefits to the ecosystem, with emphasis on recycling of nutrients. The objective of this work was to evaluate the application of different chemical products as ripeners and their effects on nutritional composition in different portions of the remaining shoots of the harvest. The variety used was RB966928, and the experimental design was a randomized block with four replicates. The treatments consisted of control, dose of 0.5 L ha-1 glyphosate, 0.02 kg ha-1 of sulfometuron-methyl and 0.80 L ha-1 of trinexapac-ethyl. The samples were separated in leaf +1, leaf canopy and pointer, being carried out the chemical analysis to determine the contents of the nutrients. The nutritional variables were evaluated as a function of time after application of the treatments until harvest at 0, 15, 30, 45 and 60 days. For both macro and micronutrients, trinexapac-ethyl kept the content of most nutrients close or even higher than the control. In general, the best performance was trinexapac-ethyl, followed by sulfometuron-methyl and glyphosate, in the analyzes of leaf +1. In relation to leaf canopy and pointer, treatments with ripeners altered the nutritional composition in the evaluated components, in which it is possible to observe values significantly higher in the leaf canopy than in the pointer. The use of trinexapac-ethyl is indicated for the maintenance of macronutrient contents, and in some cases glyphosate can be used. However... / Mestre

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Thesis (Ph.D.) -- University of Western Sydney, [2002]. / "A thesis presented to the University of Western Sydney in partial fulfillment of the requirements for the degree of Doctor of Philosophy " Includes references and appendices.

Thesis (Ph. D.)--University of Missouri-Columbia, 1996. / Typescript. Vita. Includes bibliographical references (leaves 114-123). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 1996. / Typescript. Vita. Includes bibliographical references (leaves 114-123). Also available on the Internet.

Thesis (M.S.)--University of Delaware, 2008. / Principal faculty advisor: Steven D. Brown, Dept. of Chemistry & Biochemistry. Includes bibliographical references.

Thesis (Ph.D.)--University of Missouri-Columbia, 2004. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.