Profiling Rhizosphere Chemistry: Evidence from Carbon and Nitrogen K‐Edge XANES and Pyrolysis‐FIMS
Bibliographic record
Abstract
The rhizosphere is a region of complex interactions among plants, soil, and microbiota and by its very nature, it presents many technical challenges to the analyst. Whereas previous studies have generally focused on root exudation in artificial systems, we compared whole‐soil samples from bulk and rhizosphere soils developed under field pea ( Pisum sativa L.). Synchrotron‐based C and N K‐edge x‐ray absorption near‐edge structure (XANES) spectroscopy and pyrolysis field‐ionization mass‐spectrometry (Py‐FIMS) were used to investigate plant effects on the organic chemistry of the rhizosphere in a growth chamber experiment. Soil type appeared to play a significant role in the development of the rhizosphere. Indeed, the C and N K‐edge XANES analyses revealed patterns of rhizosphere development that were strongly influenced by soil type. Relative to the bulk soil, pea rhizospheres developed on a clay soil showed increases in heterocyclic N compounds, proteins, and carboxylates. Pea rhizospheres developed on a sandy clay loam soil showed increased nitroaromatic compounds and reduced aromatics, while proteins, carbohydrates, and carboxylic compounds remained unchanged relative to the bulk soils. Pyrolysis mass spectrometry results showed that rhizosphere processes promote selective enrichment of lipid compounds (alkanes, alkenes, alkylamides, alkylaromatics, and alkyl, benzoic, and phthalic esters) with a concomitant depletion of carbohydrates, proteins, phenols, and lignins. These results suggest enhanced decomposition of labile organic matter at a molecular level in the rhizosphere, presumably as a result of enhanced microbial activity. The presence of nitroaromatic and alkylamide compounds in the rhizosphere indicates a unique cycling of N in this region. Synchrotron‐based analysis of whole soils offers useful, corroborating information regarding the organic chemistry of the rhizosphere when compared with established pyrolytic techniques.
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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 | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 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".