Further investigation of the roles of auxin and cytokinin in the NH<sub>4</sub><sup>+</sup>‐induced stimulation of nodulation using white clover transformed with the auxin‐sensitive reporter <i>GH3:gusA</i>
Bibliographic record
Abstract
Although mineral N (nitrate and ammonium) is believed to have generally negative effects on nodulation in legume–rhizobia symbioses, previous studies have shown that low, static concentrations of ammonium stimulate nodulation in pea, and that this enhancement may be due to an elevation in cytokinin to auxin levels in roots. Here, the effects of ammonium (0.0, 0.1, 0.5 and 2.5 mM) on nodulation and auxin levels were investigated in wild‐type (WT) white clover (Trifolium repens cv. Haifa) and its transformants (lines 38 and 41) which contain the auxin‐sensitive reporter gene (GH3:gusA). The effects of exogenous application (10−10, 10−9 and 10−8 M) of the cytokinin 6‐benzylaminopurine (BAP) were also assessed. Whole‐plant nodulation (nodules plant−1) and dry weight (DW)‐specific nodulation (nodules g−1 root DW) were stimulated (up to 49%) in all white clover lines by 0.1 mM NH4+. This represents the first confirmation of an NH4+‐induced stimulation of DW‐specific nodulation in a species other than pea. At 2.5 mM NH4+, the effect was lost on whole‐plant nodulation and was inhibitory on DW‐specific nodulation. Rhizobial inoculation resulted in a decline in the expression of GH3:gusA in root tips as expected; however, ammonium treatment did not affect GH3 expression in any root zones. Exogenous application of BAP at 10−9 and 10−8 M stimulated whole‐plant and DW‐specific nodulation in wild‐type white clover to a similar degree as treatment with 0.1 mM NH4+. These results support our previous hypothesis that the stimulation of nodulation by low concentrations of ammonium involves the alteration of the ratio of cytokinin to auxin, specifically by increasing cytokinin.
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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) | 0.001 | 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".