Regulation and mechanism of potassium release from barley roots: an <i>in planta</i><sup>42</sup>K<sup>+</sup> analysis
Bibliographic record
Abstract
Potassium (K(+) ) flux into plant cells is a well-characterized ion transport phenomenon. By contrast, little is known about the mechanisms and regulation of K(+) flux from the cell. Here, we present a radioisotopic analysis of K(+) fluxes from roots of intact barley (Hordeum vulgare), in the context of recent discoveries in the molecular biology and electrophysiology of this process. Plants were labelled with (42)K(+), and kinetics of its release from roots were monitored at low (0.1 mM) or high (1.0 mM) external K concentration, [K(+)](ext), and with the application of channel modulators and nutrient shifts. At 0.1 (but not 1.0) mM [K(+)], where K(+) efflux is thought to be mediated by K(+)-outward-rectifying channels, (42)K(+) efflux was inhibited by the channel blockers barium (Ba(2+)), caesium (Cs(+)), tetraethylammonium (TEA(+)), and lanthanum (La(3+)). Ammonium and nitrate (10 mM) stimulated and inhibited (42)K(+) efflux, respectively, while 10 mM [K(+)](ext) or [Rb(+) ](ext) decreased it. No evidence for the involvement of ATP-binding cassettes, nonselective cation channels, or active K(+)-efflux pumps was found. Our study provides new evidence for the thermodynamic transition between high- and low-affinity transport, from the efflux perspective, identifying the operation of channels at low [K(+)], and the cessation of transmembrane efflux at high [K(+)].
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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 | 0.001 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.001 |
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".