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Water use is an important topic in the global agriculture community and is a critical input in nursery crop production. Several plants in the genus Cornus are important nursery crops. Not only are they economically relevant, they are found in grafted and seedling forms and parents and their hybrid are readily available in the trade, facilitating an assessment of water requirements. Anecdotal information suggests that Cornus taxa have differing stress tolerance and water use requirements. Research was conducted to characterize and model water use among Cornus taxa. Scanning electron microscopy and anatomy‐based micromorphological studies as well as transpiration chamber‐based studies revealed differences in the cuticle, epidermal thickness, stomatal density, total stomatal complex area, and gas exchange. A novel photosynthesis‐based irrigation model was developed and evaluated, first on a model crop, Hibiscus rosa‐sinensis, then with a range of Cornus taxa, including grafted specimens. The model allowed the identification of a setpoint or point at which irrigation is triggered. Producing plants under this model allowed a 27% reduction in water use while maintain growth when compared with controls.

The work contained in this thesis was concerned with rebreathing methods of measuring lung volume. In particular, one novel rebreathing technique which uses oxygen as the indicator gas was assessed. This technique appeared methodologically simple and readily applicable in a clinical environment. In essence, it relied on a graphical extrapolation of the time related changes in oxygen concentration to allow for oxygen uptake. This technique has been tested using a mass spectrometer which enabled nitrogen and argon as well as oxygen to be simultaneously used as indicator gases. Although the lung volumes as measured by the different indicator gases should have been the same, these were found to be different. These discrepancies were related to the concentration of the indicator gas which existed in the bag and lung prior to rebreathing. A hypothesis explaining these inconsistancies was formulated. This was based on an initial but non-sustained output of carbon dioxide into the bag-plus-lung system. A numerical model of idealised rebreathing showed that the hypothesis was sufficient to explain the discrepancies observed. A correction procedure was devised which performed successfully in the model. This correction was incorporated into an on-line computing procedure for calculating real lung volume. When tested in normal subjects this gave consistent results for lung volume, irrespective of indicator gas employed. The corrected lung volumes were unaffected by the initial gas compositions in the bag and lung, and were also independent of non-sustained gas exchange, whether this was due to carbon dioxide and/or nitrous oxide. This technique could, therefore, be use under anaesthetic conditions, since the uptake or output of nitrous oxide no longer upsets the calculation of lung volume. The use of more than one indicator gas, within the same manoeuvre, was shown to provide a valuable indication of the presence of errors in the system. When this approach was applied to more conventional rebreathing techniques of lung volume measurement, it also highlighted the presence of inaccuracies.

Thesis (M. Sc.)--University of Adelaide, Dept. of Physiology, 1989. / Typescript (Photocopy). Includes bibliographical references (leaves 42-52).

Title from PDF of title page (University of Missouri--Columbia, viewed on Feb 26, 2010). The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Dissertation advisor: Dr. Peter Pfeifer. Vita. Includes bibliographical references.

Bibliography: leaves 69-78. Leaf gas exchange (LGE) of mango cultivars Kensington, Irwin and Tommy Atkins was investigated in a series of field experiments under varying environmental and physiological conditions in the Ord River Irrigation Area, Kununurra, Western Australia. The environmental influences on mango during fruit development are extreme producing high vapour pressure deficient (VPD) and photosynthetic photon flux density. This combined with internal pressures associated with crop load and water stress have a profound effect on LGE. Diurnal changes in atmospheric and leaf temperature are accompanied by changes in VPD in the field. Differences in cultivars in LGE response to changing environmental conditions were significant, with Kensington appearing the most sensitive to extreme atmospheric conditions. There appeared to be no cultivar differences in LGE with changing soil moisture status.

The perennating organ, the rhizome, was chosen for examination of response to anoxia in monocotyledonous species known to differ in tolerance of flooding. Survival of prolonged anoxia was monitored in the wetland species (Acorus calamus, Iris pseudacorus. Phragmites australis, Schoenoplectus lacustris and Typha latifolia), and the dryland species (Iris germanica). Fermentation capacity was estimated in the anoxic and post-anoxic phases together with ethanol and lactate accumulation. Under N2 accumulation of ethanol took place in all species; lactic fermentation was of less importance. There was a steady-state condition of low ethanol accumulation in the wetland species, where an apparent equilibrium of production and elimination from rhizome tissue was reached. In contrast, the dryland species showed a continuous increase in ethanol accumulation during oxygen deprivation. Catalase and superoxide dismutase activities were measured during the post-anoxic recovery phase in their role as enzymatic defences against oxygen toxicity. In rhizomes of the anoxia tolerant species A. calamus. S. lacustris and I. pseudacorus, no changes in catalase activity were observed. However, the relatively anoxia intolerant Glyceria maxima, Juncus effusus and I.germanica exhibited significant increases in catalase activity. To investigate whether catalase (acting in its 'peroxidatic' mode) was perhaps here involved in an ethanol oxidation reaction, anaerobic rhizomes of G.maxima were exposed to ethanol vapour: considerable increases in catalase activity were recorded. It is proposed that acetaldehyde thus produced may be a source of post-anoxic injury. Superoxide dismutase activity in I.pseudacorus rhizomes rose significantly during anoxia, while small increases were found in the less anoxia tolerant I.germanica and a drop in activity was recorded in G.maxima. It is suggested that I.pseudacorus may be less susceptible to post-anoxic injury by means of oxygen toxicity, while in the other species oxidative damage on return to air may contribute to anoxia intolerance.

The initial physiological processes leading to enhanced growth of loblolly pine subsequent to fertilization are not clearly understood. Much of the debate revolves around the temporal response of photosynthesis (Pn) to fertilization or even if Pn increases at all due to enhanced nutrition. This study tracked loblolly pine light-saturated photosynthesis (Asat), dark respiration (Rd), volume, height, basal diameter, and leaf area responses in eight clones to fertilization (112 kg/ha N) over the course of a growing season in the field. Measurements were conducted intensively before and after fertilization in order to track the initial physiological changes prior to any changes in growth in the fertilized seedlings. The results showed that fertilization does increase Pn rates although there was no significant effect on Rd rates during the study. The fertilized seedlings mean Asat rates were significantly higher on three sampling dates and remained higher throughout most of the sampling period. At the end of the growing season, the fertilized seedlings had a 30.5% higher projected crown area than the controls and 48% greater mean volumes. Physiological and growth responses were significantly different among clones with some showing large and others showing little or no response to fertilization. These results support the hypothesis from Gough et al. (2004b) that post-fertilization increases in Pn create extra photoassimilate used in building larger leaf areas. These larger leaf areas contribute to higher canopy photosynthesis levels, which leads to an increase in dry matter production. / Master of Science

Atmospheric transport and air-water exchange of organochlorine pesticides (OCPs) were investigated in temperate North America and the Arctic. OCPs studied were hexachlorocyclohexanes (HCHs, a-, b- and g-isomers), components of technical chlordane (trans- and cis-chlordane, trans-nonachlor), dieldrin, heptachlor exo-epoxide and toxaphene. Air and water samples were taken on cruises in the Great Lakes and Arctic to determine concentrations and gas exchange flux direction and magnitude. The Henry’s law constant, which describes the equilibrium distribution of a chemical between air and water, was determined for several OCPs as a function of temperature and used to assess the net direction of air-water exchange. Air samples were collected in Alabama to investigate southern U.S. sources of OCPs. Chemical markers (isomers, and enantiomers of chiral OCPs) were employed to infer sources and trace gas exchange. Elevated air concentrations of toxaphene and chlordanes were found in Alabama relative to the Great Lakes, indicating a southern U.S. source. Profiles of toxaphene compounds in air were similar to those in soil by being depleted in easily degraded species, suggesting that soil emissions control air concentrations. Gas exchange fluxes in the Great Lakes indicated near-equilibrium between air and water with excursions to net volatilization or deposition. Net volatilization of a-HCH from the Arctic Ocean was traced by evasion of non-racemic a-HCH into the atmosphere.