Abstract
Abstract— The short‐term adaptation of intact leaves to an increase in light intensity was studied by an analysis of chlorophyll fluorescence and oxygen evolution monitored by photoacoustics. An increase in light intensity led to an oxygen “gush”. This “gush” was followed by a large (up to 120%) biphasic increase in the yield of oxygen evolution characterized by a fast phase (T = 0.5–2 min) and a slow phase (T = 4–20 min). The fast phase of the increase in oxygen yield was coupled to a decrease of fluorescence, whereas the slow phase was accompanied by a parallel fluorescence increase. A comparison of fluorescence parameters with oxygen yield indicates that the slow phase of the increase in oxygen yield was coupled to an increase in the antenna size of photosystem II. The slow phase was not inhibited by the uncoupler Nigericin but it was absent in chlorophyll‐ b ‐less barley mutants deñcient in the light harvesting chlorophyll a/b protein complex of photosystem II (LHC II). These experiments indicate that changes in the LHC II mediated energy distribution, which occur in the time‐range of several minutes, are involved in the adaptation to changing light intensities. Moreover, electrophoretic analysis of 32 P orthophosphate labeled leaf discs adapted to low and high light intensities suggests that the slow phase of the increase in oxygen evolution involves dephosphorylation of the 25 kDa polypeptide of LHC II, by a small extent of 12%. The trigger for the slow phase of the increase in oxygen yield does not involve the oxidation of the plastoquinone pool. It was found that in response to the increased light intensity, the plastoquinone pool became more reduced as judged by model calculations. Experiments with the uncoupler Nigericin suggest that the control of the slow phase of adaptation to increased light intensity was also not exerted by the pH gradient across the thylakoid membrane. The similarities between the adaptation to increased light intensity and the state II to state I transition suggest that both adaptation phenomena involve LHC II dephosphorylation possibly triggered by the cytochrome b 6 / f complex.
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Claims 11
Claim · model-written summary
An increase in light intensity caused a large biphasic increase (up to 120%) in the yield of oxygen evolution in intact leaves.
- Taxon
- higher plantsEmbryophytat0
- Treatment
- increase in light intensitye0
- Outcome
- yield of oxygen evolutione1
- Direction
- increasee1
- Value
- up to 120%e1
Not reportedComparator
Verbatim
t0“ADAPTATION OF HIGHER PLANTS TO CHANGING LIGHT INTENSITIES”
e0“An increase in light intensity led to an oxygen “gush””
e1“This “gush” was followed by a large (up to 120%) biphasic increase in the yield of oxygen evolution”
Claim · model-written summary
The fast phase of the increase in oxygen yield was coupled to a decrease of fluorescence in intact leaves.
- Taxon
- higher plantsEmbryophytat0
- Organ / stage
- intact leavese3
- Outcome
- fluorescencee2
- Direction
- decreasee2
Verbatim
t0“ADAPTATION OF HIGHER PLANTS TO CHANGING LIGHT INTENSITIES”
e2“The fast phase of the increase in oxygen yield was coupled to a decrease of fluorescence”
e3“The short‐term adaptation of intact leaves to an increase in light intensity was studied”
Claim · model-written summary
The slow phase of the increase in oxygen yield was coupled to an increase in the antenna size of photosystem II in intact leaves.
- Taxon
- higher plantsEmbryophytat0
- Organ / stage
- intact leavese3
- Outcome
- antenna size of photosystem IIe4
- Direction
- increasee4
Verbatim
t0“ADAPTATION OF HIGHER PLANTS TO CHANGING LIGHT INTENSITIES”
e4“A comparison of fluorescence parameters with oxygen yield indicates that the slow phase of the increase in oxygen yield was coupled to an increase in the antenna size of photosystem II”
e3“The short‐term adaptation of intact leaves to an increase in light intensity was studied”
Claim · model-written summary
The slow phase was not inhibited by the uncoupler Nigericin.
- Taxon
- higher plantsEmbryophytat0
- Treatment
- uncoupler Nigericine5
- Outcome
- slow phasee5
- Direction
- not inhibitede5
Not reportedComparator
Verbatim
t0“ADAPTATION OF HIGHER PLANTS TO CHANGING LIGHT INTENSITIES”
e5“The slow phase was not inhibited by the uncoupler Nigericin”
Claim · model-written summary
The slow phase was absent in chlorophyll-b-less barley mutants deficient in LHC II.
- Taxon
- barley
.jpg?width=60)
Hordeum vulgaree7 - Material
- barley mutantse7
- Gene
- light harvesting chlorophyll a/b protein complex of photosystem IIe6
- Outcome
- slow phasee5
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
.jpg?width=500)
Verbatim
e5“The slow phase was not inhibited by the uncoupler Nigericin”
e6“in the light harvesting chlorophyll a/b protein complex of photosystem II (LHC II)”
e7“barley mutants”
Claim · model-written summary
Changes in LHC II-mediated energy distribution, occurring over minutes, are involved in adaptation to changing light intensities.
- Taxon
- higher plantsEmbryophytat0
- Outcome
- adaptation to changing light intensitiese0
- Qualifier
- changes in the LHC II mediated energy distributione7
Verbatim
t0“ADAPTATION OF HIGHER PLANTS TO CHANGING LIGHT INTENSITIES”
e7“changes in the LHC II mediated energy distribution”
e0“are involved in the adaptation to changing light intensities”
Claim · model-written summary
Electrophoretic analysis suggests that the slow phase of the oxygen-evolution increase involves dephosphorylation of the 25 kDa polypeptide of LHC II, by a small extent of 12%.
Verbatim
t0“ADAPTATION OF HIGHER PLANTS TO CHANGING LIGHT INTENSITIES”
e1“electrophoretic analysis of 32 P orthophosphate labeled leaf discs adapted to low and high light intensities suggests that the slow phase of the increase in oxygen evolution involves dephosphorylation of the 25 kDa polypeptide of LHC II, by a small extent of 12%”
Claim · model-written summary
The trigger for the slow phase of the oxygen-yield increase does not involve oxidation of the plastoquinone pool.
- Taxon
- higher plantsEmbryophytat0
- Outcome
- trigger for the slow phase of the increase in oxygen yielde1
- Qualifier
- oxidation of the plastoquinone poole1
Verbatim
t0“ADAPTATION OF HIGHER PLANTS TO CHANGING LIGHT INTENSITIES”
e1“The trigger for the slow phase of the increase in oxygen yield does not involve the oxidation of the plastoquinone pool”
Claim · model-written summary
In response to increased light intensity, the plastoquinone pool became more reduced, as judged by model calculations.
- Taxon
- higher plantsEmbryophytat0
- Treatment
- increased light intensitye1
- Outcome
- plastoquinone poole1
- Direction
- more reducede1
Not reportedComparator
Verbatim
t0“ADAPTATION OF HIGHER PLANTS TO CHANGING LIGHT INTENSITIES”
e1“in response to the increased light intensity, the plastoquinone pool became more reduced as judged by model calculations”
Claim · model-written summary
Nigericin experiments suggest that the control of the slow phase of adaptation to increased light intensity is not exerted by the pH gradient across the thylakoid membrane.
- Taxon
- higher plantsEmbryophytat0
- Outcome
- control of the slow phase of adaptation to increased light intensitye1
- Qualifier
- pH gradient across the thylakoid membranee1
Verbatim
t0“ADAPTATION OF HIGHER PLANTS TO CHANGING LIGHT INTENSITIES”
e1“Experiments with the uncoupler Nigericin suggest that the control of the slow phase of adaptation to increased light intensity was also not exerted by the pH gradient across the thylakoid membrane”
Claim · model-written summary
Similarities between light-intensity adaptation and the state II to state I transition suggest that both involve LHC II dephosphorylation, possibly triggered by the cytochrome b6/f complex.
- Taxon
- higher plantsEmbryophytat0
- Gene
- LHC IIe1
- Outcome
- adaptation phenomenae1
- Qualifier
- possibly triggered by the cytochrome b 6 / f complexe1
Verbatim
t0“ADAPTATION OF HIGHER PLANTS TO CHANGING LIGHT INTENSITIES”
e1“The similarities between the adaptation to increased light intensity and the state II to state I transition suggest that both adaptation phenomena involve LHC II dephosphorylation possibly triggered by the cytochrome b 6 / f complex”