Bibliographic record
Abstract
Maize is a major cereal crop that requires a well-developed root system to support the production of ≥8 tonnes of grain ha-1 in Quebec, Canada. Maize has pre-embryonic (primary and seminal) and post-embryonic (crown and brace) roots that are usually colonized by arbuscular mycorrhizal fungi. However, root colonization with arbuscular mycorrhizal fungi may be constrained by fertilizer use, particularly when phosphorus (P) fertilizers are applied and the plant-available phosphorus concentration of soil increases, based on greenhouse and growth bench experiments. Furthermore, maize root types may have different amounts of arbuscular mycorrhizal fungi colonization that are not detected with random sampling, which may create a bias in estimating the root colonization percentage. The objectives of this thesis were 1) to determine whether maize root colonization by arbuscular mycorrhizal fungi varied with the plant-available P concentration in soil, based on a gradient of Mehlich-3 extractable P levels following 3 yr of organic and inorganic P fertilizer application to agricultural field plots, 2) to determine if greater root colonization by arbuscular mycorrhizal fungi is associated with more P uptake by maize, and 3) to compare the arbuscular mycorrhizal fungi colonization in maize roots collected at random or from anatomically distinct types (primary, seminal and crown roots) from the V3 to V6 growth stages. The field experiment involved collecting maize plants from agricultural plots with a 3 yr history of organic and inorganic P fertilizer treatments that created a 20-fold difference in the plant-available P concentration, from 12 to 204 mg Mehlich-3-P kg-1. Although the proportion of maize roots colonized with arbuscular mycorrhizal fungi increased from 26 - 2% during vegetative growth (V8 and VT growth stages) to 46 - 2% in the reproductive R2 and R6 stages, root colonization was not affected by P fertilizer application. There was more arbuscular mycorrhizal fungi colonization of maize roots with an increase in plant-available P concentration in soil (r=0.12, P=0.05, n=237), and greater root colonization by arbuscular mycorrhizal fungi was associated with greater P uptake in the maize shoots (r=0.53, P<0.001, n=240). This finding may reflect the greater soil fertility in plots with higher P fertilizer inputs, rather than a direct effect of arbuscular mycorrhizal fungi on P acquisition by maize. In a controlled growth chamber experiment with non-sterile field soil, arbuscular mycorrhizal fungi colonization was evaluated from the V3 to V6 growth stages on distinct maize root types – primary, seminal, and crown – as well as a random sample of lateral roots. Root colonization by arbuscular mycorrhizal fungi increased during maize growth and was always greater in the primary and seminal roots than in the crown and mixed samples. Crown roots were 3–4 times longer with greater surface area, diameter, and volume than primary and seminal roots, but there was no difference in the lignin, cellulose, and hemicellulose content of these root types. Thus, the abundance of arbuscular mycorrhizal fungi on maize roots is affected by root sampling procedures. In summary, this work reveals that arbuscular mycorrhizal fungi are robust colonizers of maize roots, regardless of soil P levels, with preferential colonization of the pre-embryonic primary and seminal roots during early vegetative growth stages
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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".