Abstract
A reduced red to far-red (R/FR) light ratio and low photosynthetically active radiation (PAR) irradiance are both strong signals for inducing etiolation growth of plant stems. Under natural field conditions, plants can be exposed to either a reduced R/FR ratio or lower PAR, or to a combination of both. We used Helianthus annuus L., the sunflower, to study the effect of reduced R/FR ratio, low PAR or their combination on hypocotyl elongation. To accomplish this, we attempted to uncouple light quality from light irradiance as factors controlling hypocotyl elongation. We measured alterations in the levels of endogenous gibberellins (GAs), cytokinins (CKs) and the auxin indole-3-acetic acid (IAA), and the effect of exogenous hormones on hypocotyl growth. As expected, both reduced R/FR ratio and lower PAR can significantly promote sunflower hypocotyl elongation when given separately. However, providing the reduced R/FR ratio at a low PAR resulted in the greatest hypocotyl growth, and this was accompanied by significantly higher levels of endogenous IAA, GA1, GA8, GA20 and of a wide range of CKs. Providing a reduced R/FR ratio under normal PAR also significantly increased growth and again gave significantly higher levels of endogenous IAA, GAs and CKs. However, only under the de-etiolating influence of a normal R/FR ratio did lowering PAR significantly increase levels of GA1, GA8 and GA20. We thus conclude that light quality (e.g. the R/FR ratio) is the most important component of shade for controlling hypocotyl growth and elevated growth hormone content.
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Claims 8
Claim · model-written summary
Reduced red to far-red ratio significantly promoted sunflower hypocotyl elongation.
- Taxon
- sunflower
Helianthus annuuse0 - Treatment
- reduced R/FR ratioe0
- Outcome
- hypocotyl elongatione0
- Direction
- promotee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“both reduced R/FR ratio and lower PAR can significantly promote sunflower hypocotyl elongation when given separately”
Claim · model-written summary
Lower PAR significantly promoted sunflower hypocotyl elongation.
- Taxon
- sunflowerHelianthus annuuse0
- Treatment
- lower PARe0
- Outcome
- hypocotyl elongatione0
- Direction
- promotee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“both reduced R/FR ratio and lower PAR can significantly promote sunflower hypocotyl elongation when given separately”
Claim · model-written summary
Reduced R/FR at low PAR produced the greatest hypocotyl growth.
Not reportedTaxonComparator
Verbatim
e0“providing the reduced R/FR ratio at a low PAR resulted in the greatest hypocotyl growth”
Claim · model-written summary
Reduced R/FR at low PAR raised endogenous IAA, GA1, GA8, GA20 and CK levels.
Not reportedTaxonTreatmentComparator
Verbatim
e0“this was accompanied by significantly higher levels of endogenous IAA, GA1, GA8, GA20 and of a wide range of CKs”
Claim · model-written summary
Reduced R/FR under normal PAR significantly increased hypocotyl growth.
Not reportedTaxonComparator
Verbatim
e0“Providing a reduced R/FR ratio under normal PAR also significantly increased growth”
Claim · model-written summary
Reduced R/FR under normal PAR raised endogenous IAA, GAs and CKs.
Not reportedTaxonTreatmentComparator
Verbatim
e0“again gave significantly higher levels of endogenous IAA, GAs and CKs”
Claim · model-written summary
Under normal R/FR, lowering PAR significantly increased GA1, GA8 and GA20.
- Treatment
- lowering PARe0
- Outcome
- levels of GA1, GA8 and GA20e0
- Direction
- increasee0
- Qualifier
- normal R/FR ratioe0
Not reportedTaxonComparator
Verbatim
e0“only under the de-etiolating influence of a normal R/FR ratio did lowering PAR significantly increase levels of GA1, GA8 and GA20”
Claim · model-written summary
Authors conclude light quality is the most important shade component for hypocotyl growth and hormone content.
- Outcome
- most important component of shade for controlling hypocotyl growth and elevated growth hormone contente0
Not reportedTaxon
Verbatim
e0“light quality (e.g. the R/FR ratio) is the most important component of shade for controlling hypocotyl growth and elevated growth hormone content”
The same questions in other papers
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See all 19 papers →Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.