Abstract
Attached leaves of pumpkin (Cucurbita pepo L. cv. Jattiläismeloni) were exposed to high light intensity at room temperature (ca 23°C) and at 1°C. Fluorescence parameters and electron transport activities measured from isolated thylakoids indicated faster photoinhibition of PSII at low temperature. Separation of the α and β components of the complementary area above the fluorescence induction curve of dichlorophenyl-dimethylurea-poisoned thylakoids revealed that at low temperature only the α-centers declined during exposure to high light intensity while the content of functional β-centers remained constant. Freeze-fracture electron microscopy showed no decrease in the density of particles on the appressed exoplasmic fracture face, indicating that the photoinhibited α-centers remained in the appressed membranes at 1°C. Because of the function of the repair and protective mechanisms of PSII, strong light induced less photoinhibition at room temperature, but more complicated changes occurred in the α/β-heterogeneity of PSII. During the first 30 min at high light intensity the decrease in α-centers was almost as large as at 1°C, but in contrast to the situation at low temperature the decrease in α-centers was compensated for by a significant increase in PSIIβ-centers. Changes in the density and size of freeze-fracture particles suggest that this increase in β-centers was due to migration of phosphorylated light-harvesting complex from appressed to non-appressed thylakoid membranes while the PSII core remained in the appressed membranes. This situation, however, was only transient and was followed by a rapid decrease in the functionalβ-centers.
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Claims 9
Claim · model-written summary
Low temperature accelerated PSII photoinhibition.
Not reportedComparator
Verbatim
e0“faster photoinhibition of PSII at low temperature”
t0“Attached leaves of pumpkin (Cucurbita pepo L. cv. Jattiläismeloni)”
Claim · model-written summary
At low temperature, alpha centers declined under high light.
- Taxon
- pumpkint0
- Treatment
- exposure to high light intensitye0
- Outcome
- α-centerse0
- Direction
- declinede0
- Qualifier
- at low temperaturee0
Not reportedComparator
Verbatim
e0“at low temperature only the α-centers declined during exposure to high light intensity”
t0“Attached leaves of pumpkin (Cucurbita pepo L. cv. Jattiläismeloni)”
Claim · model-written summary
Functional beta centers remained constant at low temperature.
Verbatim
e0“the content of functional β-centers remained constant”
t0“Attached leaves of pumpkin (Cucurbita pepo L. cv. Jattiläismeloni)”
Claim · model-written summary
Appressed membrane particle density did not decrease at 1°C.
Verbatim
e0“no decrease in the density of particles on the appressed exoplasmic fracture face”
t0“Attached leaves of pumpkin (Cucurbita pepo L. cv. Jattiläismeloni)”
Claim · model-written summary
Strong light induced less photoinhibition at room temperature.
- Taxon
- pumpkint0
- Treatment
- strong lighte0
- Outcome
- photoinhibitione0
- Direction
- lesse0
- Qualifier
- at room temperaturee0
Not reportedComparator
Verbatim
e0“strong light induced less photoinhibition at room temperature”
t0“Attached leaves of pumpkin (Cucurbita pepo L. cv. Jattiläismeloni)”
Claim · model-written summary
Alpha centers decreased during the first 30 minutes of high light at room temperature.
Verbatim
e0“During the first 30 min at high light intensity the decrease in α-centers was almost as large as at 1°C”
t0“Attached leaves of pumpkin (Cucurbita pepo L. cv. Jattiläismeloni)”
Claim · model-written summary
PSII beta centers increased significantly at room temperature.
Verbatim
e0“a significant increase in PSIIβ-centers”
t0“Attached leaves of pumpkin (Cucurbita pepo L. cv. Jattiläismeloni)”
Claim · model-written summary
The beta-center increase was attributed to migration of phosphorylated light-harvesting complex.
Verbatim
e0“this increase in β-centers was due to migration of phosphorylated light-harvesting complex from appressed to non-appressed thylakoid membranes”
t0“Attached leaves of pumpkin (Cucurbita pepo L. cv. Jattiläismeloni)”
Claim · model-written summary
Functional beta centers then rapidly decreased.
Verbatim
e0“followed by a rapid decrease in the functionalβ-centers”
t0“Attached leaves of pumpkin (Cucurbita pepo L. cv. Jattiläismeloni)”
The same questions in other papers
light · physiology: photosynthesis · Cucurbita (pumpkins)Positive and negative results
2 in the opposite direction
- negative
- negative
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.