Uncoupling light quality from light irradiance effects in Helianthus annuus shoots: putative roles for plant hormones in leaf and internode growth
Bibliographic record
Abstract
An attempt has been made to uncouple the effects of the two primary components of shade light, a reduced red to far-red (R/FR) ratio and low photosynthetically active radiation (PAR), on the elongation of the youngest internode of sunflower (Helianthus annuus) seedlings. Maximal internode growth (length and biomass) was induced by a shade light having a reduced R/FR ratio (0.85) under the low PAR of 157 micromol m(-2) s(-1). Reducing the R/FR ratio under normal PAR (421 micromol m(-2) s(-1)) gave similar growth trends, albeit with a reduced magnitude of the response. Leaf area growth showed a rather different pattern, with maximal growth occurring at the higher (normal) PAR of 421 micromol m(-2) s(-1)), but with variable effects being seen with changes in light quality. Reducing the R/FR ratio (by enrichment with FR) gave significant increases in gibberellin A(1) (GA(1)) and indole-3-acetic acid (IAA) contents in both internodes and leaves. By contrast, a lower PAR irradiance had no significant effect on GA(1) and IAA levels in internodes or leaves, but did increase the levels of other GAs, including two precursors of GA(1). Interestingly, both leaf and internode hormone content (GAs, IAA) are positively and significantly correlated with growth of the internode, as are leaf levels of abscisic acid (ABA). However, changes in these three hormones bear little relationship to leaf growth. By implication, then, the leaf may be the major source of GAs and IAA, at least, for the rapidly elongating internode. Several other hormones were also assessed in leaves for plants grown under varying R/FR ratios and PARs. Leaf ethylene production was not influenced by changes in R/FR ratio, but was significantly reduced under the normal (higher) PAR, the irradiance treatment which increased leaf growth. Levels of the growth-active free base and riboside cytokinins were significantly increased in leaves under a reduced R/FR ratio, but only at the higher (normal) PAR irradiance; other light quality treatments evoked no significant changes. Taken in toto, these results indicate that both components of shade light can influence the levels of a wide range of endogenous hormones in internodes and leaves while evoking increased internode elongation and biomass accumulation. However, it is light quality changes (FR enrichment) which are most closely tied to increased hormone content, and especially with increased GA and IAA levels. Finally, the increases seen in internode and leaf GA content with a reduced R/FR ratio are consistent with FR enrichment inducing an overall increase in sunflower seedling GA biosynthesis.
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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 | 0.001 |
| 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".