Abstract
Germination of lettuce seeds (Lactuca sativa L. cv Grand Rapids) in the dark was nearly 100% at 20 degrees C but was inhibited at 27 degrees C and higher temperatures (thermoinhibition). A single 5-minute exposure to red light completely overcame the inhibition at temperatures up to 28 degrees C, above which the effectiveness of single light exposures gradually declined to reach a negligible level at 32 degrees C. However, the promotive effect of light could be extended to 34 degrees C by repeated irradiations. At any one temperature, increased frequency of irradiations increased germination percentage, and with each degree increase in temperature, increasingly frequent irradiations were necessary to elicit maximal germination. Loss of the effectiveness of single irradiations with increase in temperature may result either from acceleration of the thermal reversion of the far red-absorbing form of phytochrome or decrease in seed sensitivity toward a given percentage of the far red-absorbing form of phytochrome. Using continuous red light to induce germination, the role of endogenous C(2)H(4) in germination at 32 degrees C was studied. Ethylene evolution from irradiated seeds began to increase 2 hours prior to radicle protrusion, whereas the dark-incubated (nongerminating) seeds produced a low, constant amount of C(2)H(4) throughout the 24 hour incubation period. Inhibition of C(2)H(4) synthesis with 2-aminoethoxyvinyl glycine and/or inhibition of C(2)H(4) action with 2,5-norbornadiene blocked the promotive effect of light. Exogenous C(2)H(4) overcame these blockages. The results showed that participation by endogenous C(2)H(4) was essential for the light-induced relief of thermoinhibition of lettuce seed germination. However, light did not act exclusively via C(2)H(4) since exogenous C(2)H(4) alone in darkness did not promote germination.
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Claims 10
Claim · model-written summary
Dark lettuce seed germination was nearly complete at 20 degrees C and inhibited at 27 degrees C and above.
- Taxon
- lettuce
Lactuca sativae0 - Material
- Lactuca sativa L. cv Grand Rapidse0
- Outcome
- Germinatione0
- Direction
- inhibitede0
- Value
- nearly 100%e0
- Qualifier
- 27 degrees C and higher temperaturese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Germination of lettuce seeds (Lactuca sativa L. cv Grand Rapids) in the dark was nearly 100% at 20 degrees C but was inhibited at 27 degrees C and higher temperatures (thermoinhibition).”
Claim · model-written summary
One red-light exposure relieved thermoinhibition through 28 degrees C, with effectiveness declining above that.
- Taxon
- LettuceLactuca sativat0
- Treatment
- A single 5-minute exposure to red lighte0
- Outcome
- inhibitione0
- Direction
- completely overcamee0
- Qualifier
- temperatures up to 28 degrees Ce0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“A single 5-minute exposure to red light completely overcame the inhibition at temperatures up to 28 degrees C, above which the effectiveness of single light exposures gradually declined to reach a negligible level at 32 degrees C.”
t0“Lettuce Seed Germination”
Claim · model-written summary
Repeated irradiation extended light-promoted germination to 34 degrees C.
- Taxon
- LettuceLactuca sativat0
- Treatment
- repeated irradiationse0
- Outcome
- promotive effect of lighte0
- Direction
- extendede0
- Value
- 34 degrees Ce0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the promotive effect of light could be extended to 34 degrees C by repeated irradiations”
t0“Lettuce Seed Germination”
Claim · model-written summary
More frequent irradiation increased germination at a given temperature.
- Taxon
- LettuceLactuca sativat0
- Treatment
- increased frequency of irradiationse0
- Outcome
- germination percentagee0
- Direction
- increasede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At any one temperature, increased frequency of irradiations increased germination percentage”
t0“Lettuce Seed Germination”
Claim · model-written summary
Higher temperatures required more frequent irradiation for maximal germination.
- Taxon
- LettuceLactuca sativat0
- Treatment
- each degree increase in temperaturee0
- Outcome
- frequent irradiations were necessary to elicit maximal germinatione0
- Direction
- increasingly frequente0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“with each degree increase in temperature, increasingly frequent irradiations were necessary to elicit maximal germination”
t0“Lettuce Seed Germination”
Claim · model-written summary
Ethylene evolution rose before radicle protrusion in illuminated seeds.
- Taxon
- LettuceLactuca sativat0
- Treatment
- irradiatede0
- Outcome
- Ethylene evolutione0
- Direction
- increasee0
- Value
- 2 hourse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Ethylene evolution from irradiated seeds began to increase 2 hours prior to radicle protrusion”
t0“Lettuce Seed Germination”
Claim · model-written summary
Dark-incubated seeds produced a low constant amount of ethylene.
- Taxon
- LettuceLactuca sativat0
- Treatment
- dark-incubatede0
- Outcome
- C(2)H(4)e0
- Direction
- constante0
- Qualifier
- 24 hour incubation periode0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“dark-incubated (nongerminating) seeds produced a low, constant amount of C(2)H(4) throughout the 24 hour incubation period”
t0“Lettuce Seed Germination”
Claim · model-written summary
Blocking ethylene synthesis or action blocked the germination benefit of light.
- Taxon
- LettuceLactuca sativat0
- Treatment
- 2-aminoethoxyvinyl glycinee0
- Outcome
- promotive effect of lighte0
- Direction
- blockede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Inhibition of C(2)H(4) synthesis with 2-aminoethoxyvinyl glycine and/or inhibition of C(2)H(4) action with 2,5-norbornadiene blocked the promotive effect of light”
t0“Lettuce Seed Germination”
Claim · model-written summary
Exogenous ethylene overcame the inhibitor blockages.
- Taxon
- LettuceLactuca sativat0
- Treatment
- Exogenous C(2)H(4)e0
- Outcome
- blockagese0
- Direction
- overcamee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Exogenous C(2)H(4) overcame these blockages”
t0“Lettuce Seed Germination”
Claim · model-written summary
Exogenous ethylene alone in darkness did not promote germination.
- Taxon
- LettuceLactuca sativat0
- Treatment
- exogenous C(2)H(4) alone in darknesse0
- Outcome
- germinatione0
- Direction
- did not promotee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“exogenous C(2)H(4) alone in darkness did not promote germination”
t0“Lettuce Seed Germination”
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