Substantial role for carbonic anhydrase in latitudinal variation in mesophyll conductance of <i>Populus trichocarpa</i> Torr. & Gray
Bibliographic record
Abstract
Abstract In Populus trichocarpa (black cottonwood), net photosynthesis (An) varies with latitude and, in northern genotypes, is supported by higher stomatal conductance (gs). We report here a parallel cline in mesophyll conductance (gm) and link this variation to carbonic anhydrase (CA) activity. Using concurrent carbon isotope discrimination and chlorophyll fluorescence methods, we examined the effects of acetazolamide, an inhibitor of CA, on gm in six representative genotypes (three from either end of the north‐south cline). Acetazolamide reduced CA activity, gm, gs, chloroplast CO2 concentration (Cc) and An at normal CO2 (400 μmol mol−1), the latter being reversible at saturating CO2. Absolute reductions in An, gm and CA activity were greater in northern genotypes than in southern genotypes (P < 0.025) but percent reductions were similar. In contrast, northern genotypes showed lower percent reduction in Cc compared to southern genotypes (P < 0.025). The northern genotypes had greater CA activity relative to both leaf area (two‐fold) and mass (1.8‐fold) (P < 0.016). The relationship between CA activity and gm was similar whether the variation was inherent or inhibitor induced. We suggest that greater CA activity contributes to higher gm in northern P. trichocarpa genotypes, but other diffusion pathway components may also be involved.
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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 | 0.000 |
| 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".