Abstract
The effect of a temperature close to the freezing point (chilling) on the nitrate reductase system of leaf discs of Cucumis sativus L. cv. Kleine Groene Scherpe was determined in the absence and presence of light. The capacity of leaf discs in the light (250 μE m −2 s −1 ) at 20°C to increase in vivo and in vitro nitrate reductase activity, was unaffected by chilling pretreatment in the dark, but 4 h of chilling pretreatment in the light (250 μE m −2 s −1 ) decreased the capacity to less than 50% of the unchilled control. The chilling inhibition of the capacity to increase nitrate reductase activity was of a photooxidative nature since it only occurred in the presence of light and oxygen. Plants grown at a low light intensity (65 μE m −2 s −1 ) lost 95% of their capacity to increase nitrate reductase activity, while plants grown at 195 μE m −2 s −1 retained 80% of their nitrate reducing capacity after 6 h chilling pretreatment in the 250 μE m −2 s −1 light. Previously induced nitrate reductase activity was also affected by light during chilling. A lag phase of 7 h preceded a fast phase of decrease in activity. Both in vivo and in vitro activity decreased to 15% of the control value after 18 h of chilling in the light. It is concluded that the induction mechanism of nitrate reductase is primarily affected by photooxidation during chilling. The decrease in nitrate reductase activity is attributed to a decrease in the amount of activity enzyme.
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Claims 8
Claim · model-written summary
Chilling pretreatment in the dark did not affect the capacity of cucumber leaf discs in light to increase nitrate reductase activity.
- Taxon
- Cucumis sativus
Cucumis sativuse1 - Material
- Kleine Groene Scherpee1
- Organ / stage
- leaf discse1
- Treatment
- chilling pretreatment in the darke0
- Outcome
- in vivo and in vitro nitrate reductase activitye0
- Direction
- unaffectede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The capacity of leaf discs in the light (250 μE m −2 s −1 ) at 20°C to increase in vivo and in vitro nitrate reductase activity, was unaffected by chilling pretreatment in the dark”
e1“The effect of a temperature close to the freezing point (chilling) on the nitrate reductase system of leaf discs of Cucumis sativus L. cv. Kleine Groene Scherpe was determined in the absence and presence of light”
Claim · model-written summary
Four hours of chilling in light decreased the capacity of cucumber leaf discs to increase nitrate reductase activity to less than 50% of the unchilled control.
- Taxon
- Cucumis sativusCucumis sativuse1
- Material
- Kleine Groene Scherpee1
- Treatment
- 4 h of chilling pretreatment in the lighte2
- Outcome
- capacitye2
- Direction
- decreasede2
- Value
- less than 50%e2
- Comparator
- unchilled controle2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“The effect of a temperature close to the freezing point (chilling) on the nitrate reductase system of leaf discs of Cucumis sativus L. cv. Kleine Groene Scherpe was determined in the absence and presence of light”
e2“but 4 h of chilling pretreatment in the light (250 μE m −2 s −1 ) decreased the capacity to less than 50% of the unchilled control”
Claim · model-written summary
The chilling inhibition of nitrate reductase induction is photooxidative in nature, occurring only in the presence of light and oxygen.
- Taxon
- Cucumis sativusCucumis sativuse1
- Treatment
- chillinge3
- Outcome
- chilling inhibition of the capacity to increase nitrate reductase activitye3
- Qualifier
- photooxidative naturee3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“The effect of a temperature close to the freezing point (chilling) on the nitrate reductase system of leaf discs of Cucumis sativus L. cv. Kleine Groene Scherpe was determined in the absence and presence of light”
e3“The chilling inhibition of the capacity to increase nitrate reductase activity was of a photooxidative nature since it only occurred in the presence of light and oxygen”
Claim · model-written summary
Plants grown at low light intensity (65 μE m −2 s −1) lost 95% of their capacity to increase nitrate reductase activity, compared with plants grown at 195 μE m −2 s −1, after 6 h chilling in 250 μE m −2 s −1 light.
- Taxon
- Cucumis sativusCucumis sativuse1
- Treatment
- low light intensity (65 μE m −2 s −1 )e4
- Outcome
- capacity to increase nitrate reductase activitye4
- Direction
- loste4
- Value
- 95%e4
- Qualifier
- after 6 h chilling pretreatment in the 250 μE m −2 s −1 lighte4
- Comparator
- plants grown at 195 μE m −2 s −1e4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“The effect of a temperature close to the freezing point (chilling) on the nitrate reductase system of leaf discs of Cucumis sativus L. cv. Kleine Groene Scherpe was determined in the absence and presence of light”
e4“Plants grown at a low light intensity (65 μE m −2 s −1 ) lost 95% of their capacity to increase nitrate reductase activity, while plants grown at 195 μE m −2 s −1 retained 80% of their nitrate reducing capacity after 6 h chilling pretreatment in the 250 μE m −2 s −1 light”
Claim · model-written summary
Plants grown at 195 μE m −2 s −1 retained 80% of their nitrate reducing capacity after 6 h chilling in 250 μE m −2 s −1 light.
- Taxon
- Cucumis sativusCucumis sativuse1
- Treatment
- 6 h chilling pretreatment in the 250 μE m −2 s −1 lighte4
- Outcome
- nitrate reducing capacitye4
- Direction
- retainede4
- Value
- 80%e4
- Qualifier
- plants grown at 195 μE m −2 s −1e4
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“The effect of a temperature close to the freezing point (chilling) on the nitrate reductase system of leaf discs of Cucumis sativus L. cv. Kleine Groene Scherpe was determined in the absence and presence of light”
e4“Plants grown at a low light intensity (65 μE m −2 s −1 ) lost 95% of their capacity to increase nitrate reductase activity, while plants grown at 195 μE m −2 s −1 retained 80% of their nitrate reducing capacity after 6 h chilling pretreatment in the 250 μE m −2 s −1 light”
Claim · model-written summary
Previously induced nitrate reductase activity declined during chilling in light, with a lag phase of 7 h before a fast phase of decrease.
- Taxon
- Cucumis sativusCucumis sativuse1
- Outcome
- lag phasee5
- Value
- 7 he5
- Qualifier
- preceded a fast phase of decrease in activitye5
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“The effect of a temperature close to the freezing point (chilling) on the nitrate reductase system of leaf discs of Cucumis sativus L. cv. Kleine Groene Scherpe was determined in the absence and presence of light”
e5“Previously induced nitrate reductase activity was also affected by light during chilling. A lag phase of 7 h preceded a fast phase of decrease in activity”
Claim · model-written summary
Both in vivo and in vitro nitrate reductase activity decreased to 15% of the control value after 18 h of chilling in light.
- Taxon
- Cucumis sativusCucumis sativuse1
- Treatment
- 18 h of chilling in the lighte6
- Outcome
- in vivo and in vitro activitye6
- Direction
- decreasede6
- Value
- 15%e6
- Comparator
- control valuee6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“The effect of a temperature close to the freezing point (chilling) on the nitrate reductase system of leaf discs of Cucumis sativus L. cv. Kleine Groene Scherpe was determined in the absence and presence of light”
e6“Both in vivo and in vitro activity decreased to 15% of the control value after 18 h of chilling in the light”
Claim · model-written summary
The decrease in nitrate reductase activity is attributed to a decrease in the amount of active enzyme.
- Taxon
- Cucumis sativusCucumis sativuse1
- Outcome
- decrease in nitrate reductase activitye7
- Qualifier
- a decrease in the amount of activity enzymee7
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“The effect of a temperature close to the freezing point (chilling) on the nitrate reductase system of leaf discs of Cucumis sativus L. cv. Kleine Groene Scherpe was determined in the absence and presence of light”
e7“The decrease in nitrate reductase activity is attributed to a decrease in the amount of activity enzyme”
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