Abstract
Cucumber plants (Cucumis sativus L.), grown at low quantum flux density (120-150 microeinsteins per square meter per second) were photoinhibited by a three-hour exposure in air to ten times the light intensity experienced during growth. Chloroplasts were isolated from photoinhibited and control leaves and the following activities determined: O(2) evolution in the presence of ferricyanide, photosystem I activity, noncyclic and cyclic photophosphorylation, and light-induced proton uptake. Chlorophyll and chloroplast absorbance spectra, and chloroplast fluorescence were also measured. It was found that photosystem II electron transport and non-cyclic photophosphorylation were inhibited by about 50%, while cyclic photophosphorylation was less inhibited and photosystem I electron transport and light-induced proton uptake were unaffected. Electron transport to methylviologen could not be fully restored by electron donation to photosystem II. Chloroplast fluorescence induction at room temperature was strongly reduced following photoinhibition. There was no difference in the absorption spectra of the extracted chlorophylls from control and photoinhibited chloroplasts, but an increase of the absorption in the blue wavelength region was observed in the photoinhibited chloroplasts. It is suggested that high light stress does not result in alteration of the membrane properties, as is the case in low-temperature stress for example, but affects directly the photosynthetic reaction centers, primarily of photosystem II.
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Claims 10
Claim · model-written summary
High-light exposure inhibited photosystem II electron transport by about 50%.
- Taxon
- Cucumber plants
Cucumis sativuse0 - Treatment
- a three-hour exposure in air to ten times the light intensity experienced during growthe0
- Outcome
- photosystem II electron transporte0
- Direction
- inhibitede0
- Value
- about 50%e0
- Comparator
- control leavese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Cucumber plants (Cucumis sativus L.), grown at low quantum flux density (120-150 microeinsteins per square meter per second) were photoinhibited by a three-hour exposure in air to ten times the light intensity experienced during growth. Chloroplasts were isolated from photoinhibited and control leaves and the following activities determined: O(2) evolution in the presence of ferricyanide, photosystem I activity, noncyclic and cyclic photophosphorylation, and light-induced proton uptake. Chlorophyll and chloroplast absorbance spectra, and chloroplast fluorescence were also measured. It was found that photosystem II electron transport and non-cyclic photophosphorylation were inhibited by about 50%”
Claim · model-written summary
Non-cyclic photophosphorylation was inhibited by about 50%.
Not reportedTaxon
Verbatim
e0“It was found that photosystem II electron transport and non-cyclic photophosphorylation were inhibited by about 50%”
Claim · model-written summary
Cyclic photophosphorylation was less inhibited.
Not reportedTaxon
Verbatim
e0“while cyclic photophosphorylation was less inhibited”
Claim · model-written summary
Photosystem I electron transport and light-induced proton uptake were unaffected.
Not reportedTaxon
Verbatim
e0“photosystem I electron transport and light-induced proton uptake were unaffected”
Claim · model-written summary
Electron transport to methylviologen was not fully restored by donation to photosystem II.
Not reportedTaxon
Verbatim
e0“Electron transport to methylviologen could not be fully restored by electron donation to photosystem II”
Claim · model-written summary
Photoinhibition strongly reduced chloroplast fluorescence induction.
Not reportedTaxon
Verbatim
e0“Chloroplast fluorescence induction at room temperature was strongly reduced following photoinhibition”
Claim · model-written summary
Extracted chlorophyll absorption spectra did not differ between control and photoinhibited chloroplasts.
Not reportedTaxon
Verbatim
e0“There was no difference in the absorption spectra of the extracted chlorophylls from control and photoinhibited chloroplasts”
Claim · model-written summary
Photoinhibited chloroplasts had greater blue-region absorption.
Not reportedTaxon
Verbatim
e0“an increase of the absorption in the blue wavelength region was observed in the photoinhibited chloroplasts”
Claim · model-written summary
The authors suggest high light directly affects photosynthetic reaction centers, principally photosystem II.
Not reportedTaxon
Verbatim
e0“It is suggested that high light stress does not result in alteration of the membrane properties, as is the case in low-temperature stress for example, but affects directly the photosynthetic reaction centers, primarily of photosystem II”
Claim · model-written summary
The authors suggest high light does not alter membrane properties.
Not reportedTaxon
Verbatim
e0“high light stress does not result in alteration of the membrane properties”
The same questions in other papers
light · physiology: photosynthesis · Cucumis sativus (cucumber)Positive and negative results
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See all 61 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.