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Plant Age Affects the Long-term Growth Responses to Reduced Total Pressure and Oxygen Partial Pressure

Show simple item record Wehkamp, Cara Ann 2009-08-11 2009-09-14T15:26:57Z 2009-09-14T15:26:57Z 2009-09-14T15:26:57Z
dc.description.abstract Fundamental to the future of space exploration is the development of advanced life support systems capable of maintaining crews for significant periods without re-supply from Earth. Bioregenerative life support systems harness natural ecosystem processes and employ plant photosynthesis and transpiration to produce food, supply oxygen, and regenerate water while consuming carbon dioxide. Proposed Lunar and Martian exploration has prompted interest into the effects of hypobaria on plant development. Reduced atmospheric pressure conditions will reduce the pressure gradient between the structure and the local environment thereby decreasing the engineering requirements, leakage and mass required to construct the growth facility. To establish the optimal conditions for reduced pressure plant growth structures it is essential to determine the atmospheric pressure limits required for plant development and growth. Due to its physiological importance, oxygen will compose a significant portion of this atmosphere. The effects of reduced atmospheric pressure and decreased oxygen partial pressures on plant germination, growth and development were assessed in the University of Guelph’s hypobaric plant growth chambers. Treatments included a range of total pressures from 10 to 98 kPa and oxygen partial pressures from 2 to 20 kPa. Results demonstrated that reduced atmospheric pressure had minimal effect on plant growth, net carbon exchange rate and transpiration if the physiologically important gases including carbon dioxide, oxygen and water vapour, were maintained above threshold levels. The reduction of oxygen partial pressures below 7 kPa had drastic consequences across all atmospheric pressures with poor germination, seedling establishment and growth. It is evident that the response of plants grown at reduced pressures from young seedlings differs from that of older plants that were established at ambient conditions and then subjected to the atmospheric adjustment. The young plant tissues adapt in response to the extreme conditions and maintain productivity despite the limited atmosphere. en
dc.description.sponsorship Natural Science and Engineering Research Council, Canadian Space Agency, Ontario Graduate Student Program, Canadian Foundation for Innovation, Ontario Innovation Trust en
dc.language.iso en en
dc.subject Transpiration en
dc.subject Net carbon exchange rate en
dc.subject Low pressure en
dc.subject Radish (Raphanus sativa) en
dc.subject Bioregenerative Life Support en
dc.subject Hypoxia en
dc.subject Hypobaria en
dc.title Plant Age Affects the Long-term Growth Responses to Reduced Total Pressure and Oxygen Partial Pressure en
dc.type Thesis en Environmental Biology en Doctor of Philosophy en Department of Environmental Biology en

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