Typewritten copy / 318 leaves : ill. ; 26 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Faculty of Agricultural Science, 1958

1.The organic acid metabolism of the roots of wet-land species (helophytes) and that of dry-land species (non-helophytes) has been examined in relation to their tolerance to periods of experimental flooding. Growth differences between helophytes and non-helophytes were apparent only after an 18-day flood period, yet within four days of flooding differences could be observed in the levels of certain organic acids. Flooding in helophytes increased the level of root malic acid, and decreased that of succinic and lactic acid, whereas the reverse was found in non-helophytes. 2. There was evidence that under natural flooded conditions the root tissues of some wet-land species contain larger amounts of malic acid than when the flood water has receded and ground aeration improves. Shikimic acid has been detected in aquatic macrophytes and the fluctuating levels of shikimate in Iris pseudacorus and Nuphar lutea are discussed. 3. The organic acid changes related to flood tolerance operate only under partial anoxia, and under the strictly anaerobic conditions imposed by incubation of root tissue under nitrogen, there was a general reduction in all acid levels except lactate. It is suggested that non-helophytes cannot tolerate flooding through an inability to continue TCA cycle respiration during periods of reduced oxygen supply, and through the poisoning effects of ethanol accumulation. Helophyte species appear to be metabolically adapted to overcome periods of flood-induced anoxia, and tissue respiration continues with the provision for malic acid accumulation and no build-up of ethanol. 5. A tolerance of flooding, involving adaptations of the organic acid metabolism of the roots, has been demonstrated in helophyte species. This metabolic adaptation is rapidly induced, thus offering immediate protection upon flooding anoxia, and its importance in determining the ecological amplitude of a species and its possible role in future production of flood tolerant strains, are discussed.

No description available.

Water availability for uptake by tree seedlings is determined both by the soil water potential in relation to seedling needle water potential and by the resistance to flow of water through the soil, root and stem, to the needles. This study was designed to focus principally on water uptake resistances. The effects of soil texture and tree species on this water uptake resistance were quantified through the use of an Ohm's Law model suited to water flow through the soil-plant system. The study was conducted on one-year-old potted seedlings in a controlled environment growth chamber. Needle water potential (ΨN) of Douglas-fir is not much affected by soil water potential (Ψs) down to about -2.5 MPa, where the calculated water uptake rate becomes very small. However, soil texture does significantly affect the resistance to flow into the seedling and thus affects the water uptake rate by the seedling. The total resistance to water uptake increases as the soil dries. Coarser textured soils show consistently higher water uptake resistances over the soil water potential range -0.5 to -2.5 MPa. It is inferred that differences in resistance are associated with unsaturated, hydraulic conductivity characteristics of the soil and soil-root contact. Unlike Douglas-fir, both western and mountain hemlock show a large decrease in needle water potential as the soil dries down to a Ψs of about -3.0 MPa. The water potential difference (Ψs - ΨN) for hemlocks is less where Ψs is higher than -1.8 MPa, and greater where Ψs is less than -1.8 MPa, than (Ψs - ΨN ) for Douglas-fir in these s s N experiments. Despite these differences, the resistance to water uptake for both hemlock species is much greater over the soil water potential range -0.5 to -2.5 MPa, and thus the water uptake rates are much less than for Douglas-fir with the same soil, even though root densities and root surface areas are much larger for the hemlocks. This behavior is most pronounced with mountain hemlock. These differences are thought to be related to higher tissue and (perhaps) soil-root contact resistances in the hemlock species. The soil resistance appears to be small, at least down to Ψs of about -2.0 MPa, in these experiments. However, root densities are probably much greater than one might expect in the field. / Forestry, Faculty of / Graduate

Call number: LD2668 .T4 1961 M59

Plants under variable water stress exhibit a contraction of their stem diameter. This variation can be monitored to determine the plant water status which, in turn, will lead us to a method of scheduling subsequent irrigation. In this dissertation, the possibility of determining the water status in cotton plants by automatically sensing their stem diameter variation was explored. A full description of the displacement sensor, the electronic circuits used for automatic stem diameter monitoring and the data analysis is given. Simultaneous measurement of the leaf water potential and the stem diameter variation were done for a total of eight days during an irrigation cycle. Statistical analysis was performed to infer the water status in the plant from the stem diameter variation. It was discovered that the stem diameter variation lags the water potential by two hours, and that there was no simple linear correlation between them. In fact, it was discovered that the stem diameter variation was not only a function of the leaf water potential of the plant as it was believed; but indeed, it is also a function of the soil water condition. According to the results obtained, a basic model to describe the relationship between the stem diameter variation and the plant and soil water condition was developed.

No description available.

No description available.

A Coulostatic Impulse Generator (CIG) is an electronic device that transfers electrical charge to and from a pair of electrodes inserted in plant tissue. Six discrete charge transfers can be implemented in any desired sequence. The major purpose of the CIG is to determine the electrochemical constituents of the plant apoplast electrolyte. The objective of this thesis is threefold: (1) to design, construct and test the supervisory circuitry of the CIG, (2) to design, construct and test the interface between the NEC portable computer and the CIG, (3) to generate utility software to control each circuit board in the system. To handle the extreme difference in the timing of the charge transfer (microseconds) and the subsequent plant response a three step timing sequence is employed which permits an independent range of sample times and sample numbers. Data acquired is first stored in RAM in the computer within the CIG and then transferred to the external computer. (Abstract shortened with permission of author.)

Orientador: Rafael Silva Oliveira / Texto em português e inglês / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-25T08:28:23Z (GMT). No. of bitstreams: 1 Teodoro_GrazielleSales_D.pdf: 9847099 bytes, checksum: dea93bd8d08793dfcbbfed314d895252 (MD5) Previous issue date: 2014 / Resumo: Eventos de secas extremas têm ocorrido com frequência nos últimos anos em regiões tropicais. Plantas em montanhas tropicais são particularmente sensíveis a mudanças no clima e pouco se sabe sobre a resistência e resiliência de comunidades vegetais ricas em espécies, como os campos rupestres, a condições climáticas extremas. Nosso objetivo foi avaliar as respostas fenológicas e ecofisiológicas e o crescimento de seis espécies abundantes de campo rupestre sob condições de seca extrema, sendo duas rosetas (Vellozia nivea e Vellozia aff. variabilis) e quatro arbustivas (Campomanesia pubecens, Eremanthus seidelii, Mimosa clausenii e Vernonia warmingiana). Para simular eventos de seca extrema, realizamos um experimento de exclusão de chuva, constituído por 12 parcelas (4x4 metros), sendo quatro controle e oito de exclusão, em uma area de campo rupestre no Parque Nacional da Serra da Canastra. Avaliamos o desempenho ecofisiológico das plantas submetidas a condições climáticas contrastantes mediante um conjunto de atributos morfofisiológicos, incluindo: trocas gasosas, composição isotópica do carbono (?13CCELL) e oxigênio (?18OCELL) da celulose foliar (medidas integradoras da assimilação de carbono e condutância estomática), curvas de vulnerabilidade à cavitação, curvas pressão-volume, carboidratos não-estruturais (CNE), crescimento e fenologia foliar. As espécies estudadas mostraram-se bastante resistente à seca, pois após 17 meses de exclusão de chuva não encontramos diferenças de crescimento e mortalidade entre populações nas parcelas controle e experimentais. As espécies apresentaram um contínuo de estratégias de uso de água, variando de espécies isohídricas (E. seidellii) à anisohídricas (C. pubecens). O uso da abordagem isotópica dupla (?13CCELL e ?18OCELL) foi válida para avaliar e predizer as respostas fotossintéticas e estomáticas à seca apenas para as espécies isohídricas. Além disso, a composição isotópica da celulose da folha pode ser influenciada pela mobilização de reservas de CNE nas raízes. As duas espécies congenéricas de Velloziaceae apresentaram estratégias constrastantes para lidar com a seca: uma espécie é tolerante à dessecação (TD) (V. nivea) e a Vellozia aff. variabilis é não-TD. A espécie TD apresentou maiores taxas de trocas gasosas durante a estação chuvosa e durante a seca prolongada entrou em estado de "dormência", exibindo um comportamento oportunista de uso de água. Já a espécie não-DT apresentou uma estratégia conservadora de uso de água. Durante a seca, observamos um aumento no estoque de CNE% nas raízes na espécie TD, o que pode representar um mecanismo chave para sobrevivência dessa espécie durante os ciclos de dessecação e rehidratação. As três espécies arbustivas (C. pubecens, E. seidellii, V. warmingiana) apresentaram sistemas hidráulicos contrastantes, com diferentes pontos de perda de turgor (?TLP) e vulnerabilidade à cavitação (estimada mediante o P50 - potencial hídrico que corresponde à 50% de perda de condutividade). As espécies mais resistentes à cavitação (maior P50) apresentam menores reservas de CNE nas raízes, sugerindo um trade-off entre atributos hidráulicos e de estoque de carbono. Nossos resultados trazem importantes contribuições para o entendimento de funcionamento de ecossistemas sazonais limitados por água e ilustram a diversidade de estratégias hidráulicas que conferem resiliência à seca / Abstract: In the past years, extreme droughts have been frequently recorded in several tropical regions. Plants in tropical mountains are particularly sensitive to changes in climate little is known about the plant physiological adjustments and responses to changes in rainfall patterns. Our objective was to evaluate the phenological and ecophysiological responses of six dominant species with contrasting life forms in campos rupestres under an extreme drought condition. We studied two rosettes species (Vellozia nivea and Vellozia aff. variabilis) and four shrubs (Campomanesia pubecens, Eremanthus seidelii, Mimosa clausenii e Vernonia warmingiana). We implemented a rainwater exclusion experiment with 12 plots (4x4 meters), in which eight was considered drought treatment and four control treatment. We monitored several aspects of the plant ecophysiology, such as gas exchange using instantaneous measurements and stable isotope as integrators of leaf functioning, pressure-volume curves, vulnerability curves, non-structural carbohydrates (NSC) in roots, growth, biomass and leaf phenology. Species showed a continuum of water use strategies, varying from anysohydric (C. pubecens) to completely isohydric (E. seidelii) species. The relationship between ?18OCELL and gsMAX was negative and significant only for isohydric species. The use of dual isotopic approach also was valid only for isohydric species. Across species, we found a strong positive relationship between ?18OCELL and NSC% for individuals under drought treatment, suggesting that the use of NSC% reserves in water stress conditions can affect leaf isotope composition. Our results suggest that in communities dominated to species with a great diversity of hydraulic strategies, such as the campos rupestres, ?18OCELL should be used with caution to infer physiological responses. We evaluated a congeneric pair of Velloziaceae species with contrasting strategies to cope with the erratic water availability in campos rupestres. One species is desiccation tolerant (DT) and the other is drought resistance (non-DT). The DT species showed high gsMAX and low WUEi during the rainny season, showing a profligate water use. By contrast, the non-DT showed a conservative water use throughout the year. The DT species also increased the %NSC storage in roots during the prolonged drought, presumably a key mechanism that allow survival to desiccation in this species. The three shrub species (C. pubecens, E. seidelii and M. clausenii) showed different P50 (water potential that corresponds 50% of conductivity loss) and ?TLP (water potential at turgor loss point). The biomass, in general, was little affected by our drought treatment. This three species showed a trade-off between the vulnerability to cavitation and NSC storage, in which, species more resistant to cavitation (more negative P50) showed lower NSC% storage in roots. Our results illustrate the diversity of strategies that plants might present to deal with drought and bring important contributions to understand the functioning of water-limited environments / Doutorado / Biologia Vegetal / Doutora em Biologia Vegetal