The effects of ontogeny and environmental oscillations on plant responses to oxygen deprivation were investigated for a wide spectrum of species, ranging from agricultural to forestry crops, and from temperate to tropical plants. The extent to which hypoxia- or anoxia-tolerance were affected by ontogeny and environmental oscillations, was assessed mainly through changes in survival and growth and physiological parameters such as respiratory activity, ethanol production and carbohydrate depletion. Anoxia-tolerance of germinating seeds of chickpea (Cicer arietlnum L.) was found to vary, even within the earlier stages of germination, according to the length of the aerobic imbibition period previous to the anoxic shock. The notable fact was that 6 minutes of seed aerobic imbibition prior to anoxic treatment was sufficient to significantly increase post-anoxic survival after 4 days anoxia, compared to seeds not allowed to previously imbibe aerobically. These survival results were mirrored by the significant increase in the oxygen uptake by the embryos of seeds which were allowed to imbibe aerobically for 2 hours prior to anoxia, compared to the embryos of anaerobically imbibed seeds. Germination stage also affected the response of barley (Hordeum vulgare L.) to washing under anoxia, a treatment used to investigate membrane stability and other factors associated with anoxic injury. Temperature, frequency of washing and nutrients present in the washing solution also affect the post-anoxic responses of barley. Daily washing of seedlings under anoxia was often detrimental to post-anoxic survival. One washing only, at the end of the anoxic period, often enhanced survival. This positive effect seemed to be more linked to protection against plasmamembrane leakage due to calcium ions present in the washing solution than to removal of anaerobically-produced potentially toxic volatiles. Two Brazilian tree species were also studied. The seeds of Parkia pendula (Willd.) Benth. ex. Walp., a species typically present in unflooded areas in the Amazon, were still able to germinate after seven months submergence. P.pendula one-month old seedlings, however, did not survive longer than one month flooding, which can be a considerable disadvantage in the ca. six-month long flooding period of the Amazon floodplains. However, adult trees can still be found, although rarely, in flooded areas. The possible strategies involved in an eventual establishment of P.pendula individuals in flooded areas of the Brazilian Amazon are discussed. A contrast is drawn between the responses to flooding of this species and flood-tolerant Parkia discolor. Enterolobium contortisiliquum (Veil.) Morong, is a tree species which is present in both the dry soils of the cerrados (neotropical savannas) in Central Brazil and in the flood-prone Gallery Forests. This species showed considerable tolerance to flooding and drought, as reflected by the various morphological and metabolic adaptations observed in response to these stresses. The role of the xylopodium, a rigid wood tuber, in such tolerance to flood and drought stresses is discussed. Water-stressed roots of some crop species studied presented higher ethanol levels than control plants. Additionally, these same drought-treated roots showed a considerable amount of shrinkage compared to control roots, as measured by root diameter. It is argued that drought causes root shrinkage, which possibly reduces ability of such roots to capture oxygen and results in hypoxia in the tissues and consequent increase in ethanol production. This hypothesis of drought-induced hypoxia is compared with several recent findings in the literature, and is discussed as a possible factor which allows drought, under specific circumstances, to acclimatise plants to a subsequent flooding. From preliminary experiments with alternation of flooding and drought in Eucalyptus species, it appeared that a previous stress affects a plant's response to a subsequent stress. This effect was not always negative, and in E.regnans a five-week drought allowed a subsequent 3-fold increase in flooding survival. This experiment, however, needs to be repeated in order to confirm these results. A common cause for anaerobic injury seems to be unlikely for the diverse plants studied, and anoxia survival often seemed to be related to a combination of morphological and metabolic adaptations. A critical reflection on the risks of labelling plants as tolerant or sensitive to oxygen deprivation is provided, as well as a discussion on the perspectives of applied research which may further the development of ecophysiological theory.

Thesis (M.S.)--Montana State University--Bozeman, 2007. / Typescript. Chairperson, Graduate Committee: Mark L. Skidmore. Includes bibliographical references (leaves 69-75).

The atmospheric (CO2) partial pressure is expected to continue to increase and the scenario is that the CO2 partial pressure will reach 50-70 Pa during the 21st century.The rise in CO2 will have a direct influence on plant growth and development because CO2 is the primary substrate for photosynthesis.The aim of the studies described in this thesis was to investigate the response of grasses belonging to two subtypes to a range of CO2 partial pressures under conditions where light intensity, water and N supplies were varied.Two species which are naturalized in Australia, Panicum coloratum (NAD-ME) and Cenchrus ciliaris (NADP-ME) were chosen for a series of experiments conducted in matched growth chambers. The response of C4 plants is particularly important for Australia because they dominate the tropical grasslands that occupy 75% of the continent and form the basis for the pasture industry. Following the extensive research conducted in this study, it can be concluded that the inevitable rise in atmospheric CO2 partial pressure will increase the growth of C4 grasses when other resources are not limiting.Growth of C4 grasses will be stimulated to a greater extent under conditions of drought. / Doctor of Philsophy (PhD)

Thesis (MSc) -- Macquarie University, Division of Environmental and Life Sciences, Dept. of Chemistry and Biomolecular Sciences, 2008. / Bibliography: p. 120-124.

Thesis (Ph. D.)--Earth and Atmospheric Sciences, Georgia Institute of Technology, 2008. / Stieglitz, Marc, Committee Member ; Guillas, Serge, Committee Member ; Fu, Rong, Committee Member ; Curry, Judith, Committee Member ; Dickinson, Robert, Committee Chair.

Many ecological systems follow a seasonal cycle affecting primary production, carbon flux, and vegetative gas emissions. The seasonal variation of ecological systems are both affected by and have effects upon climatic factors. A quantitative estimate of the seasonal variation of vegetation is required to characterize ecological systems and their interaction with climate. Monitoring the spaliotemporal variation of foliar biomass density (FBD) over one year will provide a quantitative estimate of the annual cycle and regional variation of photosynthetic activity. FBD is a quantitative measure of leafy material per unit of area produ\:ed by photosynthetically active vegetation. This seasonal variation in FBD is an important parameter for global and other large scale investigations of ecological, hydrological, and biogeochemical systems which require data and expertise from a variety of sources and disciplines. Therefore, FBD is potentially of great utility for ecologists, hydrologists, climatologists, and atmospheric scientists. Recent regional scale investigations of ecological systems concluded that the repetitive coverage and synoptic view of remotely sensed measurements provide data to monitor the seasonal variation of biomass. A method to estimate the seasonal variation of FBD at global scales has not been developed. The objective of this research is to develop a methodology that could be used to estimate the seasonal variation of FBD for the entire terrestrial biosphere. By coupling global satellite data, measured field data, and a vegetation classification, a model was developed to estimate the global spatiotemporal variation of FBD. Comparisons between literature estimates of FBD and estimated FBD from this model were made as a means of validation. A more specific comparison was conducted between grasslands based on work conducted in the Senegalese Sahel region in Africa. Finally, a sensitivity analysis was performed to characterize the potential propagation of error associated with the literature FBD estimates used to drive this model. / Graduation date: 1992

Thesis (Ph.D.) -- University of Western Sydney, Hawkesbury, 2000. / Thesis submitted in fulfilment of the requirement for the degree of Doctor of Philosophy, Centre For Horticulture and Plant Sciences, University of Western Sydney, 2000. Bibliography : leaves 215-231.

Thesis (M.S.)--University of Wyoming, 2007. / Title from PDF title page (viewed on Nov. 26, 2008). Includes bibliographical references (p. 24-33).

Thesis (Ph. D.)--University of Oregon, 2008. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 128-156). Also available online in Scholars' Bank; and in ProQuest, free to University of Oregon users.

Thesis (Ph. D.)--Duke University, 2008.