<i>Tribulus</i> (Zygophyllaceae) as a case study for the evolution of C<sub>2</sub> and C<sub>4</sub> photosynthesis
Bibliographic record
Abstract
Abstract C 2 photosynthesis is a photosynthetic pathway in which photorespiratory CO 2 release and refixation are enhanced in leaf bundle sheath (BS) tissues. The evolution of C 2 photosynthesis has been hypothesized to be a major step in the origin of C 4 photosynthesis, highlighting the importance of studying C 2 evolution. In this study, physiological, anatomical, ultrastructural, and immunohistochemical properties of leaf photosynthetic tissues were investigated in six non‐C 4 Tribulus species and four C 4 Tribulus species. At 42°C, T. cristatus exhibited a photosynthetic CO 2 compensation point in the absence of respiration ( C * ) of 21 µmol mol −1 , below the C 3 mean C * of 73 µmol mol −1 . Tribulus astrocarpus had a C * value at 42°C of 55 µmol mol −1 , intermediate between the C 3 species and the C 2 T. cristatus . Glycine decarboxylase (GDC) allocation to BS tissues was associated with lower C * . Tribulus cristatus and T. astrocarpus allocated 86% and 30% of their GDC to the BS tissues, respectively, well above the C 3 mean of 11%. Tribulus astrocarpus thus exhibits a weaker C 2 (termed sub‐C 2 ) phenotype. Increased allocation of mitochondria to the BS and decreased length‐to‐width ratios of BS cells, were present in non‐C 4 species, indicating a potential role in C 2 and C 4 evolution.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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 teacher head, 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".