Abstract
High-light-induced decrease in photosystem II (PSII) electron transfer activity was studied in high- and low-light-grown pumpkin (Cucurbita pepo L.) plants in vivo and in vitro. The PSII light-harvesting antenna of the low-light leaves was estimated to be twice as big as that of the high-light leaves. The low-light leaves were more susceptible to photoinhibition in vivo. However, thylakoids isolated from these two plant materials were equally sensitive to photoinhibition when illuminated in the absence of external electron acceptors. Only the intensity of the photoinhibitory light and the chlorophyll concentration of the sample, not the size of the light-harvesting antenna, determined the rate of PSII photoinhibition in vitro. Because excitation of the reaction center and not only the antenna chlorophylls is a prerequisite for photoinhibition of PSII activity, independence of photoinhibition on antenna size provides support for the hypothesis (Schatz EH, Brock H, Holzwarth AR [1988] Biophys J 54: 397-405) that the excitations of the antenna chlorophylls are in equilibrium with the excitations of the reaction centers. Better tolerance of the high-light leaves in vivo was due to a more active repair process and more powerful protective mechanisms, including photosynthesis. Apparently, some protective mechanism of the high-light-grown plants is at least partially active at low temperature. The protective mechanisms do not appear to function in vitro.
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Claims 10
Claim · model-written summary
Low-light leaves had twice the PSII antenna size of high-light leaves.
- Taxon
- pumpkin (Cucurbita pepo L.)
Cucurbita pepot0 - Organ / stage
- low-light leavese0
- Outcome
- PSII light-harvesting antennae0
- Direction
- twice as bige0
- Value
- twicee0
- Comparator
- high-light leavese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The PSII light-harvesting antenna of the low-light leaves was estimated to be twice as big as that of the high-light leaves”
t0“pumpkin (Cucurbita pepo L.) plants in vivo and in vitro”
Claim · model-written summary
Low-light leaves were more susceptible to photoinhibition in vivo.
- Taxon
- pumpkin (Cucurbita pepo L.)Cucurbita pepot0
- Organ / stage
- low-light leavese0
- Outcome
- susceptible to photoinhibitione0
- Direction
- more susceptiblee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The low-light leaves were more susceptible to photoinhibition in vivo”
t0“pumpkin (Cucurbita pepo L.) plants in vivo and in vitro”
Claim · model-written summary
Thylakoids from low- and high-light plants were equally sensitive in vitro.
- Taxon
- pumpkin (Cucurbita pepo L.)Cucurbita pepot0
- Organ / stage
- thylakoidse0
- Outcome
- sensitive to photoinhibitione0
- Direction
- equallye0
- Qualifier
- absence of external electron acceptorse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“thylakoids isolated from these two plant materials were equally sensitive to photoinhibition when illuminated in the absence of external electron acceptors”
t0“pumpkin (Cucurbita pepo L.) plants in vivo and in vitro”
Claim · model-written summary
Photoinhibitory light intensity determined in vitro PSII photoinhibition rate.
- Taxon
- pumpkin (Cucurbita pepo L.)Cucurbita pepot0
- Treatment
- intensity of the photoinhibitory lighte0
- Outcome
- rate of PSII photoinhibitione0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Only the intensity of the photoinhibitory light and the chlorophyll concentration of the sample, not the size of the light-harvesting antenna, determined the rate of PSII photoinhibition in vitro”
t0“pumpkin (Cucurbita pepo L.) plants in vivo and in vitro”
Claim · model-written summary
Sample chlorophyll concentration determined in vitro PSII photoinhibition rate.
- Taxon
- pumpkin (Cucurbita pepo L.)Cucurbita pepot0
- Compound
- chlorophylle0
- Outcome
- rate of PSII photoinhibitione0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the chlorophyll concentration of the sample, not the size of the light-harvesting antenna, determined the rate of PSII photoinhibition in vitro”
t0“pumpkin (Cucurbita pepo L.) plants in vivo and in vitro”
Claim · model-written summary
Antenna size did not determine in vitro PSII photoinhibition rate.
- Taxon
- pumpkin (Cucurbita pepo L.)Cucurbita pepot0
- Organ / stage
- light-harvesting antennae0
- Outcome
- rate of PSII photoinhibitione0
- Direction
- note0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“not the size of the light-harvesting antenna, determined the rate of PSII photoinhibition in vitro”
t0“pumpkin (Cucurbita pepo L.) plants in vivo and in vitro”
Claim · model-written summary
More active repair was attributed as a reason for better in vivo tolerance in high-light leaves.
- Taxon
- pumpkin (Cucurbita pepo L.)Cucurbita pepot0
- Organ / stage
- high-light leavese0
- Outcome
- Better tolerancee0
- Qualifier
- more active repair processe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Better tolerance of the high-light leaves in vivo was due to a more active repair process”
t0“pumpkin (Cucurbita pepo L.) plants in vivo and in vitro”
Claim · model-written summary
More powerful protective mechanisms including photosynthesis were attributed to high-light leaf tolerance.
- Taxon
- pumpkin (Cucurbita pepo L.)Cucurbita pepot0
- Organ / stage
- high-light leavese0
- Outcome
- Better tolerancee0
- Qualifier
- more powerful protective mechanisms, including photosynthesise0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Better tolerance of the high-light leaves in vivo was due to a more active repair process and more powerful protective mechanisms, including photosynthesis”
t0“pumpkin (Cucurbita pepo L.) plants in vivo and in vitro”
Claim · model-written summary
Some protective mechanism was at least partially active at low temperature.
- Taxon
- pumpkin (Cucurbita pepo L.)Cucurbita pepot0
- Outcome
- protective mechanisme0
- Qualifier
- at least partially active at low temperaturee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“some protective mechanism of the high-light-grown plants is at least partially active at low temperature”
t0“pumpkin (Cucurbita pepo L.) plants in vivo and in vitro”
Claim · model-written summary
Protective mechanisms did not appear to function in vitro.
- Taxon
- pumpkin (Cucurbita pepo L.)Cucurbita pepot0
- Outcome
- protective mechanisms do not appear to functione0
- Setting
- in vitroe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The protective mechanisms do not appear to function in vitro”
t0“pumpkin (Cucurbita pepo L.) plants in vivo and in vitro”