Estimation of the whole‐plant CO<sub>2</sub>compensation point of tobacco (<i>Nicotiana tabacum</i>L.)
Bibliographic record
Abstract
Abstract The whole‐plant CO2compensation point (Γplant) is the minimum atmospheric CO2level required for sustained growth. The minimum CO2requirement for growth is critical to understanding biosphere feedbacks on the carbon cycle during low CO2episodes; however, actual values of Γplantremain difficult to calculate. Here, we have estimated Γplantin tobacco by measuring the relative leaf expansion rate at several low levels of atmospheric CO2, and then extrapolating the leaf growth vs. CO2response to estimate CO2levels where no growth occurs. Plants were grown under three temperature treatments, 19/15, 25/20 and 30/25°C day/night, and at CO2levels of 100, 150, 190 and 270 μmol CO2 mol−1 air. Biomass declined with growth CO2such that Γplantwas estimated to be approximately 65 μmol mol−1for plants grown at 19/15 and 30/25°C. In the first 19 days after germination, plants grown at 100 μmol mol−1had low growth rates, such that most remained as tiny seedlings (canopy size <1 cm2). Most seedlings grown at 150 μmol mol−1and 30/25°C also failed to grow beyond the small seedling size by day 19. Plants in all other treatments grew beyond the small seedling size within 3 weeks of planting. Given sufficient time (16 weeks after planting) plants at 100 μmol mol−1eventually reached a robust size and produced an abundance of viable seed. Photosynthetic acclimation did not increase Rubisco content at low CO2. Instead, Rubisco levels were unchanged except at the 100 and 150 μmol mol−1where they declined. Chlorophyll content and leaf weight per area declined in the same proportion as Rubisco, indicating that leaves became less expensive to produce. From these results, we conclude that the effects of very low CO2are most severe during seedling establishment, in large part because CO2deficiency slows the emergence and expansion of new leaves. Once sufficient leaf area is produced, plants enter the exponential growth phase and acquire sufficient carbon to complete their life cycle, even under warm conditions (30/25°C) and CO2levels as low as 100 μmol mol−1.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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".