Plant Age Affects the Long-term Growth Responses to Reduced Total Pressure and Oxygen Partial Pressure
Bibliographic record
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\ndioxide, 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.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".