Abstract
The mechanism of the rapid inhibition of hypocotyl elongation by blue light was investigated in cucumber (Cucumis sativus L.) and sunflower (Helianthus annuus L.) seedlings by measuring the changes in turgor during the response. A special device, based on the resonance frequency principle, was built which permitted simultaneous and continuous measurements of both tissue rigidity (turgor) and growth rate on a single intact hypocotyl. The large decrease in growth rate following blue irradiation was consistently accompanied by a small increase in resonance frequency. This result indicates that blue light inhibits growth by decreasing the yielding properties of the cell walls, resulting in a slight rise in turgor because of the coupling between growth rate and turgor.The nature of the blue-light inhibition was further studied by measuring the influence of light dose and temperature on the time course of inhibition (lag-time, half-time of inhibition, and amount of inhibition) with the aid of a microcomputer-based system for measuring growth rate and for controlling light duration and energy. The light dose has no influence on either the lag-time or the half-time of inhibition, but strongly affects the amount of inhibition. In contrast, a 10 degrees C drop in temperature (from 30 to 20 degrees C) lengthened the lag-time of the blue-light response, but did not significantly affect the half-time or the per cent inhibition by blue light. The half-time for changes in hypocotyl length (induced by applying a hydrostatic pressure to the roots or to the cut end of seedlings with roots excised) was found to be the same as the half-time of the blue-light inhibition (15 to 25 seconds in cucumber; 90 to 150 seconds in sunflower). These results support the idea that blue light, after a fixed lag period, induces an immediate decrease in the yielding properties of the cell walls. The growth rate subsequently decreases with a half-time that depends on the time required for cell turgor pressures to reach their new steady-state values.
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Claims 9
Claim · model-written summary
Blue irradiation sharply lowered hypocotyl growth rate while resonance frequency rose slightly.
- Taxon
- Cucumis sativus L.
Cucumis sativuse1 - Treatment
- blue irradiatione0
- Outcome
- growth ratee0
- Direction
- decreasee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The large decrease in growth rate following blue irradiation was consistently accompanied by a small increase in resonance frequency.”
e1“in cucumber (Cucumis sativus L.) and sunflower (Helianthus annuus L.) seedlings”
Claim · model-written summary
Blue irradiation sharply lowered hypocotyl growth rate while resonance frequency rose slightly in sunflower.
- Taxon
- Helianthus annuus L.
Helianthus annuuse1 - Treatment
- blue irradiatione0
- Outcome
- resonance frequencye0
- Direction
- increasee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The large decrease in growth rate following blue irradiation was consistently accompanied by a small increase in resonance frequency.”
e1“in cucumber (Cucumis sativus L.) and sunflower (Helianthus annuus L.) seedlings”
Claim · model-written summary
Light dose did not influence lag-time or half-time of blue-light inhibition.
- Taxon
- Cucumis sativus L.Cucumis sativuse1
- Treatment
- light dosee0
- Outcome
- lag-time or the half-time of inhibitione0
- Direction
- no influencee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The light dose has no influence on either the lag-time or the half-time of inhibition”
e1“in cucumber (Cucumis sativus L.) and sunflower (Helianthus annuus L.) seedlings”
Claim · model-written summary
Light dose strongly affected the amount of inhibition.
- Taxon
- Cucumis sativus L.Cucumis sativuse1
- Treatment
- light dosee0
- Outcome
- amount of inhibitione0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The light dose has no influence on either the lag-time or the half-time of inhibition, but strongly affects the amount of inhibition.”
e1“in cucumber (Cucumis sativus L.) and sunflower (Helianthus annuus L.) seedlings”
Claim · model-written summary
A temperature fall from 30 to 20 degrees Celsius lengthened the blue-light response lag-time.
- Taxon
- Cucumis sativus L.Cucumis sativuse1
- Treatment
- 10 degrees C drop in temperaturee0
- Outcome
- lag-time of the blue-light responsee0
- Direction
- lengthenede0
- Comparator
- 30 to 20 degrees Ce0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a 10 degrees C drop in temperature (from 30 to 20 degrees C) lengthened the lag-time of the blue-light response”
e1“in cucumber (Cucumis sativus L.) and sunflower (Helianthus annuus L.) seedlings”
Claim · model-written summary
The temperature drop did not significantly affect response half-time or percent inhibition.
- Taxon
- Cucumis sativus L.Cucumis sativuse1
- Treatment
- blue lighte0
- Outcome
- half-time or the per cent inhibitione0
- Direction
- did not significantly affecte0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“did not significantly affect the half-time or the per cent inhibition by blue light”
e1“in cucumber (Cucumis sativus L.) and sunflower (Helianthus annuus L.) seedlings”
Claim · model-written summary
Cucumber hypocotyl length and blue-light inhibition had the same half-time, 15 to 25 seconds.
- Taxon
- cucumberCucumis sativuse0
- Organ / stage
- hypocotyle0
- Outcome
- half-time for changes in hypocotyl lengthe0
- Value
- 15 to 25 secondse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The half-time for changes in hypocotyl length (induced by applying a hydrostatic pressure to the roots or to the cut end of seedlings with roots excised) was found to be the same as the half-time of the blue-light inhibition (15 to 25 seconds in cucumber; 90 to 150 seconds in sunflower).”
Claim · model-written summary
Sunflower hypocotyl length and blue-light inhibition had the same half-time, 90 to 150 seconds.
- Taxon
- sunflowerHelianthus annuuse0
- Organ / stage
- hypocotyle0
- Outcome
- half-time for changes in hypocotyl lengthe0
- Value
- 90 to 150 secondse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The half-time for changes in hypocotyl length (induced by applying a hydrostatic pressure to the roots or to the cut end of seedlings with roots excised) was found to be the same as the half-time of the blue-light inhibition (15 to 25 seconds in cucumber; 90 to 150 seconds in sunflower).”
Claim · model-written summary
The authors infer that blue light immediately decreases cell-wall yielding after a fixed lag, then growth slows as turgor reaches a new steady state.
- Taxon
- Cucumis sativus L.Cucumis sativuse1
- Outcome
- growth rate subsequently decreasese0
- Qualifier
- yielding properties of the cell wallse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“blue light, after a fixed lag period, induces an immediate decrease in the yielding properties of the cell walls. The growth rate subsequently decreases with a half-time that depends on the time required for cell turgor pressures to reach their new steady-state values.”
e1“in cucumber (Cucumis sativus L.) and sunflower (Helianthus annuus L.) seedlings”
The same questions in other papers
light · disease · Cucumis sativus (cucumber)Positive and negative results
5 papers in the same direction as this paper · 5 in the opposite direction
- positive
- positive
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7 papers more in this group
See all 11 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.