The Relationship between Chlorophyll a Fluorescence and the Lower Oxygen Limit in Higher Plants
Bibliographic record
Abstract
The lower oxygen limit (LOL) in plants marks the oxygen (O2) level where the\nmetabolism shifts from being predominantly aerobic to anaerobic; recent work has shown\nthat respiratory-based indicators of this metabolic shift are well-correlated with changes\nin chlorophyll a fluorescence signals. The physiological and biochemical changes at the\nroot of this relationship have not been well-described in the literature. The processes\ninvolved are spatially separated: chlorophyll fluorescence is associated with the lightdependent\nreactions and emanates from the chloroplasts whereas aerobic respiration and\nfermentation occurs in the mitochondria and cytosol, respectively. Evidences outlined in\nthis thesis are used to suggest the mechanistic link between these three regions of the cell\nis a fluid exchange of cellular reductant. When mitochondrial respiration is inhibited as a\nresult of inadequate O2, used as a terminal electron acceptor, glycolytic reductant in the\nform of NADH accumulates in the cytosol. Reductant imbalances between the cytosol\nand organelles can be adjusted indirectly using translocators. Excess chloroplastic\nreductant is used to reduce the plastoquinone (PQ) pool via NADPH-dehydrogenase, a\ncomponent of the chlororespiratory pathway, effectively decreasing the photochemical\nquenching (qP) capacity thereby inducing a switch from minimum fluorescence (Fo) to a\nhigher relative fluorescence (F) value where qP < 1. Subjecting dark-adapted\nphotosystems to low-intensity light increased Fo to a slightly higher F value due to a lightinduced\nreduction of the oxidized PQ pool when the O2 was above the LOL, but\ndecreased F as a result of a PSI-driven oxidation of the already over-reduced PQ pool\nwhen the O2 was below the LOL. Low O2 was also shown to increase violaxanthin deepoxidation\nand non-photochemical quenching (qN), likely a reflection of the overreduced\nstate of the photosystems and associated pH decrease.\nDynamic controlled atmosphere (DCA) is a fluorescence-based controlled atmosphere\n(CA) system that sets the optimum atmosphere for fruits and vegetables based on a\nproduct’s fluorescence response. Experiments in this thesis on the relationship between\nO2, temperature, light, metabolism, pigmentation and chlorophyll fluorescence were used\nto interpret the physiology behind fluorescence changes, suggest improved DCA\ntechniques and outline potentially profitable avenues for future research.
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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 | 0.001 | 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 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 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".