Phenylalanine ammonia‐lyase‐induced freezing tolerance in jack pine (<i>Pinus banksiana</i>) seedlings treated with low, ambient levels of ultraviolet‐B radiation
Bibliographic record
Abstract
Phenylalanine ammonia‐lyase (PAL) induction in UVB‐exposed plants leads to an increased synthesis of UV‐absorbing phenols. As phenols, including anthocycanins, are linked to many protective mechanisms in plants, we tested the hypothesis that UVB‐induced phenol accumulation, mediated by PAL, may confer freezing tolerance in jack pine ( Pinus banksiana Lamb) seedlings. The hypothesis was tested by applying UVB in the presence and absence of the PAL‐inhibitor, 2‐aminoindan‐2‐phosphonic acid (AIP). Jack pine seedlings were grown for 3 weeks with and without 10 µ M aqueous AIP. Each treatment was then divided into two groups. One group received near‐ambient UVB (5.5 kJ m −2 day −1 of biologically effective radiation) for up to 30 h. A second, control group of seedlings received no UVB. Anthocyanin concentration declined by > 99% in PAL‐inhibited seedlings and other methanol‐extractable UV‐absorbing phenols declined by > 48%, relative to the controls. A 20‐h exposure to UVB increased seedling freezing (−15°C) tolerance in the absence of the PAL‐inhibitor, as shown by a 30% reduction in membrane injury, determined by electrolyte leakage measurements. In PAL‐inhibited seedlings, by contrast, the same UVB pre‐treatment increased freezing injury by 48%. A longer (30 h) UVB exposure was damaging to both AIP‐treated and untreated seedlings. Root feeding with 10 µ M AIP during a 3‐week exposure of older (6‐month‐old) seedlings similarly reduced phenol accumulation in UVB‐exposed seedlings. The decline in phenol production in PAL‐inhibited seedlings correlated with increased freezing injury. These results suggest a role for ambient UVB in seedling frost hardiness, mediated by a PAL‐induced production of phenolic compounds.
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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 | 0.000 |
| 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".