Low‐temperature photosynthetic performance of a C<sub>4</sub>grass and a co‐occurring C<sub>3</sub>grass native to high latitudes
Bibliographic record
Abstract
ABSTRACT The photosynthetic performance of C4plants is generally inferior to that of C3species at low temperatures, but the reasons for this are unclear. The present study investigated the hypothesis that the capacity of Rubisco, which largely reflects Rubisco content, limits C4photosynthesis at suboptimal temperatures. Photosynthetic gas exchange, chlorophyllafluorescence, and thein vitroactivity of Rubisco between 5 and 35 °C were measured to examine the nature of the low‐temperature photosynthetic performance of the co‐occurring high latitude grasses,Muhlenbergia glomerata(C4) andCalamogrostis canadensis(C3). Plants were grown under cool (14/10 °C) and warm (26/22 °C) temperature regimes to examine whether acclimation to cool temperature alters patterns of photosynthetic limitation. Low‐temperature acclimation reduced photosynthetic rates in both species. The catalytic site concentration of Rubisco was approximately 5.0 and 20 µmol m−2inM. glomerataandC. canadensis, respectively, regardless of growth temperature. In both species,in vivoelectron transport rates below the thermal optimum exceeded what was necessary to support photosynthesis. In warm‐grownC. canadensis, the photosynthesis rate below 15 °C was unaffected by a 90% reduction in O2content, indicating photosynthetic capacity was limited by the capacity of Pi‐regeneration. By contrast, the rate of photosynthesis inC. canadensisplants grown at the cooler temperatures was stimulated 20–30% by O2reduction, indicating the Pi‐regeneration limitation was removed during low‐temperature acclimation. InM. glomerata,in vitroRubisco activity and gross CO2assimilation rate were equivalent below 25 °C, indicating that the capacity of the enzyme is a major rate limiting step during C4photosynthesis at cool temperatures.
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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".