Physiological Limitations to Photosynthetic Carbon Assimilation in Cotton under Water Stress
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Bibliographic record
Abstract
Water stress may reduce leaf net photosynthetic carbon assimilation (A N ) through both stomatal effects, which reduce the leaf internal CO 2 concentration (C i ), and nonstomatal effects, which result in reduced A N at a given level of C i However, the leaf gas exchange techniques used to calculate C i are susceptible to important artifacts when applied to water‐stressed leaves, making such C i estimates unreliable. As an alternative to C i , the CO 2 concentration in the chloroplast (C C ) can be calculated from simultaneous measurements of A N from gas exchange measurements, and the thylakoid electron flux from chlorophyll fluorometry. This permits diffusional effects (stomatal plus mesophyll limitations to CO 2 diffusion) to be differentiated from chloroplast‐level effects. We used this method to investigate physiological restrictions to photosynthesis in leaves of water stressed cotton ( Gossypium hirsutum L.) plants in a series of greenhouse experiments. A null‐balance lysimeter was used to slowly induce four distinct levels of water stress. Combined leaf gas exchange/chlorophyll fluorescence measurements differentiated the treatments more effectively than gas exchange measurements alone. All treatments reduced C C , but only the two most severe stress treatments significantly increased nondiffusional restrictions, detectable as a reduction in the slope of A N on C C In a second experiment, recovery of leaf photosynthesis was determined 24 and 48 h after relief of a severe stress by rewatering. Recovery of the A N /C C relationship was substantial but incomplete after 24 h and did not recover further by 48 h after rewatering, indicating lasting chloroplast‐level injury as a result of the stress. Similar experiments should be conducted under field conditions to determine if water stress results in irreversible chloroplast‐level injury in field‐grown cotton.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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 it