The intriguing paradox of leaf lifespan responses to nitrogen availability
Bibliographic record
Abstract
1. Here we address two main questions which have received little attention: the variability of leaf lifespan (LLS) response to nitrogen (N) availability and the frequent apparent divergence between evolutionary and plastic responses of LLS to N availability. 2. By analysing numerous ecophysiological studies conducted in laboratories and in the field, we show that: (i) there is no constancy among studies and species in the LLS response to N availability; and (ii) in contrast to what is expected in an evolutionary perspective (i.e. species with shorter LLS growing on high N conditions), species that delay leaf senescence and thus increase LLS in response to high N availability are more numerous than species that behave oppositely. 3. We propose that in a given species, N sink–source interactions in the plant and exogenous N availability regulate LLS and induce a curvilinear plastic response of LLS to N availability, the maximum LLS occurring when the strength of sink activity on endogenous N reserves is minimal. We suggest that LLS responses to N supply could depend on where the plants were located on the gradient of the strength of sink activity, which depends on soil N availability. We provide several possible explanations for why long but not short LLS are selected in N-depleted habitats, even though short LLS seems to increase certain aspects of plant fitness. Particularly, we attempt to resolve the apparent conflict between plastic and evolutionary LLS responses in the light of the relationship between LLS and nutrient source–sink interactions and also between LLS and mean residence time of N in the plant. 4. Our new concept helps to explain many of the discrepancies of plastic and evolutionary LLS responses to N availability seen in the literature.
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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 | 0.001 | 0.002 |
| 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 | 0.001 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.000 |
| 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".