Abstract
Cytokinin has been reported to mimic some of the effects of light on de-etiolation responses in dark-grown Arabidopsis seedlings. The interaction between cytokinin and light was examined by analyzing cytokinin dose and light fluence effects on hypocotyl elongation in wild-type and mutant Arabidopsis seedlings with defects in light or hormone responses. It was found that (a) cytokinin and light-response systems have independent and additive effects on the inhibition of hypocotyl elongation and (b) either cytokinin or light can saturate the morphogenic responses. As a consequence, cytokinin has no effect on hypocotyl elongation under normal growth conditions because light levels saturate the hypocotyl inhibition response. To determine whether a functional light-response pathway is required for cytokinin responses, light-insensitive long hypocotyl (hy) mutants were tested for cytokinin responses. The hy mutants (hy1 to hy6) had normal cytokinin responses, except phyB-1 (hy3-1), in which hypocotyl elongation was insensitive to cytokinin. Cytokinin insensitivity in phyB-1 was attributed to an indirect effect of the mutation on cytokinin responses. The effects of cytokinin on the inhibition of hypocotyl elongation are largely mediated by ethylene, and blocking the ethylene-response pathway through the action of a cytokinin-resistant, ethylene-insensitive mutant (ckr1/ein2) had no effect on the light inhibition of hypocotyl elongation. These results do not support the idea that cytokinin mediates the action of light on hypocotyl elongation.
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Claims 8
Claim · model-written summary
Cytokinin and light independently and additively inhibit hypocotyl elongation.
- Taxon
- Arabidopsis
Arabidopsist0 - Treatment
- cytokinin and light-response systemse0
- Outcome
- hypocotyl elongatione0
- Direction
- inhibitione0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“cytokinin and light-response systems have independent and additive effects on the inhibition of hypocotyl elongation”
t0“Arabidopsis Seedlings”
Claim · model-written summary
Either cytokinin or light can saturate morphogenic responses.
- Taxon
- ArabidopsisArabidopsist0
- Treatment
- cytokinin or lighte0
- Outcome
- morphogenic responsese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“either cytokinin or light can saturate the morphogenic responses”
t0“Arabidopsis Seedlings”
Claim · model-written summary
Cytokinin has no effect on hypocotyl elongation under normal growth conditions because light saturates inhibition.
- Taxon
- ArabidopsisArabidopsist0
- Treatment
- cytokinine0
- Outcome
- hypocotyl elongatione0
- Direction
- no effecte0
- Qualifier
- normal growth conditionse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“cytokinin has no effect on hypocotyl elongation under normal growth conditions because light levels saturate the hypocotyl inhibition response”
t0“Arabidopsis Seedlings”
Claim · model-written summary
Most hy mutants retained normal cytokinin responses.
- Taxon
- ArabidopsisArabidopsist0
- Material
- hy mutants (hy1 to hy6)e0
- Outcome
- normal cytokinin responsese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The hy mutants (hy1 to hy6) had normal cytokinin responses, except phyB-1 (hy3-1)”
t0“Arabidopsis Seedlings”
Claim · model-written summary
phyB-1 hypocotyl elongation was insensitive to cytokinin.
- Taxon
- ArabidopsisArabidopsist0
- Material
- phyB-1 (hy3-1)e0
- Treatment
- cytokinine0
- Outcome
- hypocotyl elongatione0
- Direction
- insensitivee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“phyB-1 (hy3-1), in which hypocotyl elongation was insensitive to cytokinin”
t0“Arabidopsis Seedlings”
Claim · model-written summary
phyB-1 cytokinin insensitivity was attributed to an indirect mutation effect.
- Taxon
- ArabidopsisArabidopsist0
- Material
- phyB-1e0
- Outcome
- Cytokinin insensitivitye0
- Qualifier
- indirect effect of the mutatione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Cytokinin insensitivity in phyB-1 was attributed to an indirect effect of the mutation on cytokinin responses”
t0“Arabidopsis Seedlings”
Claim · model-written summary
Ethylene largely mediates cytokinin inhibition of hypocotyl elongation.
- Taxon
- ArabidopsisArabidopsist0
- Treatment
- cytokinine0
- Compound
- ethylenee0
- Outcome
- inhibition of hypocotyl elongatione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The effects of cytokinin on the inhibition of hypocotyl elongation are largely mediated by ethylene”
t0“Arabidopsis Seedlings”
Claim · model-written summary
Blocking ethylene response in ckr1/ein2 did not alter light inhibition of hypocotyl elongation.
- Taxon
- ArabidopsisArabidopsist0
- Material
- ckr1/ein2e0
- Treatment
- blocking the ethylene-response pathwaye0
- Outcome
- light inhibition of hypocotyl elongatione0
- Direction
- no effecte0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“blocking the ethylene-response pathway through the action of a cytokinin-resistant, ethylene-insensitive mutant (ckr1/ein2) had no effect on the light inhibition of hypocotyl elongation”
t0“Arabidopsis Seedlings”
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