Photosynthetic performance at low temperature of<i>Bouteloua gracilis</i>Lag., a high‐altitude C<sub>4</sub>grass from the Rocky Mountains, USA
Bibliographic record
Abstract
ABSTRACT The mechanisms controlling the photosynthetic performance of C4plants at low temperature were investigated using ecotypes ofBouteloua gracilisLag. from high (3000 m) and low (1500 m) elevation sites in the Rocky Mountains of Colorado. Plants were grown in controlled‐environment cabinets at a photon flux density of 700μmol m−2s−1and day/night temperatures of 26/16 °C or 14/7 °C. The thermal response of the net CO2assimilation rate (A) was evaluated using leaf gas‐exchange analysis and activity assays of ribulose‐1,5‐bisphosphate carboxylase/oxygenase (Rubisco), phosphoenolpyruvate carboxylase (PEPCase) and pyruvate,orthophosphate dikinase (PPDK). In both ecotypes, a reduction in measurement temperature caused the CO2‐saturated rate of photosynthesis to decline to a greater degree than the initial slope ofAversus the intercellular CO2response, thereby reducing the photosynthetic CO2saturation point. As a consequence,Ain normal air was CO2‐saturated at sub‐optimal temperatures. Ecotypic variation was low when grown at 26/16 °C, with the major difference between the ecotypes being that the low‐elevation plants had higherA;however, the ecotypes responded differently when grown at cool temperature. At temperatures below the thermal optimum,Ain high‐elevation plants grown at 14/7 °C was enhanced relative to plants grown at 26/16 °C, whileAin low‐elevation plants grown at 14/7 °C was reduced compared to 26/16 °C‐grown plants. Photoinhibition at low growth temperature was minor in both ecotypes as indicated by small reductions in dark‐adaptedFv/Fm. In both ecotypes, the activity of Rubisco was equivalent toAbelow 17 °C but well in excess ofAabove 25 °C. Activities of PEPCase and PPDK responded to temperature in a similar proportion relative to Rubisco, and showed no evidence for dissociation that would cause them to become principal limitations at low temperature. Because of the similar temperature response of Rubisco andA, we propose that Rubisco is a major limitation on C4photosynthesis inB. gracilisbelow 17 °C. Based on these results and for theoretical reasons associated with how C4plants use Rubisco, we further suggest that Rubisco capacity may be a widespread limitation upon C4photosynthesis at low temperature.
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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) | 0.000 | 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 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".