Abstract
After rice plants (japonica rice Azucena) were treated with various concentrations of polyethylene glycol (PEG) for 16 days, characteristics of gas exchange, chlorophyll fluorescence, MDA content and activities of antioxidant enzymes (SOD, POD and CAT) in the leaves were measured. The reasons for photosynthetic declination caused by different PEG concentrations were remarkably different, varying in three phases. In the first phase, under 10% PEG treatment, net photosynthetic rate (P_(n)) significantly decreased, but stomatal conductance (G_(s)) and intercellular CO_(2) concentration (C_(i)) increased slightly, while chlorophyll fluorescence parameters and photosynthetic pigment content showed little change, suggesting that the decrease in P_(n) was not due to the stomatal limitation. In the second phase, under 15% PEG treatment, the pigment content and fluorescence parameters began to change but P_(n) decreased with a significant decrease in G_(s) and C_(i), indicating G_(s) became a main factor limiting P_(n). In the last phase, under 20% PEG treatment, P_(n), G_(s), fluorescence parameters and pigment content fell signifiantly further, whereas C_(i) exhibited no further decrease, demonstrating that the decline in P_(n) was largely attributed to the damage of photosynthetic membrane. Although severe water stress caused the reduction of the abilities for harvesting and transferring light energy, the excess excitation energy still occurred and might lead to the production of reactive oxygen species triggering the antioxidant system. However, it could still damage photosynthetic apparatus and result in the reduction of photochemical activity of PS II.
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Claims 12
Claim · model-written summary
At 10% PEG, rice net photosynthetic rate declined significantly.
- Taxon
- rice
Oryza sativat0 - Treatment
- 10% PEG treatmente0
- Outcome
- net photosynthetic ratee0
- Direction
- decreasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“under 10% PEG treatment, net photosynthetic rate (P_(n)) significantly decreased”
t0“rice”
Claim · model-written summary
At 10% PEG, stomatal conductance and intercellular CO2 concentration rose slightly.
- Taxon
- riceOryza sativat0
- Treatment
- 10% PEG treatmente1
- Outcome
- stomatal conductance (G_(s)) and intercellular CO_(2) concentration (C_(i))e0
- Direction
- increased slightlye0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“stomatal conductance (G_(s)) and intercellular CO_(2) concentration (C_(i)) increased slightly”
e1“under 10% PEG treatment”
t0“rice”
Claim · model-written summary
At 10% PEG, chlorophyll fluorescence parameters and photosynthetic pigment content changed little.
- Taxon
- riceOryza sativat0
- Treatment
- 10% PEG treatmente1
- Outcome
- chlorophyll fluorescence parameters and photosynthetic pigment contente0
- Direction
- little changee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“chlorophyll fluorescence parameters and photosynthetic pigment content showed little change”
e1“under 10% PEG treatment”
t0“rice”
Claim · model-written summary
At 10% PEG, the authors attributed reduced photosynthesis to factors other than stomatal limitation.
- Taxon
- riceOryza sativat0
- Treatment
- 10% PEG treatmente1
- Outcome
- decrease in P_(n)e0
- Qualifier
- not due to the stomatal limitatione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the decrease in P_(n) was not due to the stomatal limitation”
e1“under 10% PEG treatment”
t0“rice”
Claim · model-written summary
At 15% PEG, rice pigment content and fluorescence parameters began to change.
- Taxon
- riceOryza sativat0
- Treatment
- 15% PEG treatmente0
- Outcome
- pigment content and fluorescence parameterse0
- Direction
- began to changee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“under 15% PEG treatment, the pigment content and fluorescence parameters began to change”
t0“rice”
Claim · model-written summary
At 15% PEG, net photosynthetic rate, stomatal conductance, and intercellular CO2 concentration declined.
- Taxon
- riceOryza sativat0
- Treatment
- 15% PEG treatmente1
- Outcome
- P_(n)e0
- Direction
- decreasede0
- Qualifier
- significant decrease in G_(s) and C_(i)e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“P_(n) decreased with a significant decrease in G_(s) and C_(i)”
e1“under 15% PEG treatment”
t0“rice”
Claim · model-written summary
At 15% PEG, stomatal conductance became a principal limitation on photosynthesis.
- Taxon
- riceOryza sativat0
- Treatment
- 15% PEG treatmente1
- Outcome
- P_(n)e0
- Qualifier
- G_(s) became a main factore0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“G_(s) became a main factor limiting P_(n)”
e1“under 15% PEG treatment”
t0“rice”
Claim · model-written summary
At 20% PEG, photosynthetic rate, stomatal conductance, fluorescence parameters, and pigment content fell further.
- Taxon
- riceOryza sativat0
- Treatment
- 20% PEG treatmente0
- Outcome
- P_(n), G_(s), fluorescence parameters and pigment contente0
- Direction
- fell signifiantly furthere0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“under 20% PEG treatment, P_(n), G_(s), fluorescence parameters and pigment content fell signifiantly further”
t0“rice”
Claim · model-written summary
At 20% PEG, intercellular CO2 concentration did not decline further.
- Taxon
- riceOryza sativat0
- Treatment
- 20% PEG treatmente1
- Outcome
- C_(i)e0
- Direction
- no further decreasee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“C_(i) exhibited no further decrease”
e1“under 20% PEG treatment”
t0“rice”
Claim · model-written summary
At 20% PEG, the authors attributed photosynthetic decline largely to photosynthetic membrane damage.
- Taxon
- riceOryza sativat0
- Treatment
- 20% PEG treatmente1
- Outcome
- decline in P_(n)e0
- Qualifier
- damage of photosynthetic membranee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the decline in P_(n) was largely attributed to the damage of photosynthetic membrane”
e1“under 20% PEG treatment”
t0“rice”
Claim · model-written summary
Severe water stress reduced light-energy harvesting and transfer ability in rice.
- Taxon
- riceOryza sativat0
- Treatment
- severe water stresse0
- Outcome
- abilities for harvesting and transferring light energye0
- Direction
- reductione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“severe water stress caused the reduction of the abilities for harvesting and transferring light energy”
t0“rice”
Claim · model-written summary
The authors proposed that excess excitation energy could produce reactive oxygen species, trigger antioxidants, and damage photosystem II activity.
- Taxon
- riceOryza sativat0
- Outcome
- photochemical activity of PS IIe0
- Qualifier
- might lead to the production of reactive oxygen speciese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the excess excitation energy still occurred and might lead to the production of reactive oxygen species triggering the antioxidant system. However, it could still damage photosynthetic apparatus and result in the reduction of photochemical activity of PS II”
t0“rice”
The same questions in other papers
poly(ethylene glycol) · physiology: gas exchange · Oryza sativa (rice)Positive and negative results
2 in the opposite direction
- negative
- no effect
poly(ethylene glycol) · physiology: pigments · Oryza sativa (rice)Results agree
2 papers in the same direction as this paper
- negative
- negative
poly(ethylene glycol) · physiology: photosynthesis · Oryza sativa (rice)Results agree
3 papers in the same direction as this paper
- negative
- 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.