Abstract
【Objective】 The purpose of this study is to explore the photosynthetic response and mechanism of cucumber seedlings to double CO2 concentration combined with drought stresses.【Method】 Using split plot design,the effects of doubled CO2 concentration on photosynthesis of cucumber(Cucumis sativus L.'Jinyou No.1') seedlings under drought stresses were investigated.The main plot was two CO2 concentrations(ambient CO2 concentration,≈380 μmol·mol-1,and doubled CO2 concentration,760±20 μmol·mol-1),and the split-plot was three water treatments(control,moderate drought stress and severe drought stress) simulated by PEG 6000.【Result】 Drought stresses remarkably reduced net photosynthetic rate,transpiration rate and stomatal conductance of leaves of cucumber seedlings.Under the condition of doubled CO2 concentration,net photosynthetic rate dramatically increased while transpiration rate and stomatal conductance decreased,thereby water use efficiency dramatically increased.The interact effects of doubled CO2 concentration and drought stress on net photosynthetic rate,transpiration rate,water use efficiency as well as stomatal conductance were all significant(P0.01).Drought stresses significantly reduced apparent quantum efficiency,maximum assimilation rate,maximum rate of carboxylation by Rubisco,PAR-saturated rate of electron transport,rate of triose phosphate utilization and light saturated points of leaves of cucumber seedlings,but enhanced light compensatory points.Under control and mild drought stress conditions,doubled CO2 concentration dramatically improved apparent quantum efficiency and maximum assimilation rate,but there were no significant differences under severe drought stress.Under control condition,doubled CO2 concentration dramatically enhanced maximum rate of carboxylation by Rubisco,PAR-saturated rate of electron transport and rate of triose phosphate utilization,but reduced CO2 compensatory points and respiration rate,there were no significant differences under drought stresses except CO2 compensatory points reduced by 4.9% under moderate drought stress.【Conclusion】 The decrease of net photosynthesis under moderate drought stress was due to stoma restriction,while it was due to stoma and non-stoma combined restriction under severe drought stress.Drought stresses resulted in dramatic decline of photosynthetic electron transport and photophosphorylation capacity of cucumber seedlings.Doubled CO2 concentration improved water use efficiency of cucumber seedlings by improving net photosynthetic rate and reducing transpiration rate,and improved apparent quantum efficiency and CO2 assimilation maximum of cucumber seedlings under moderate drought stress condition to meliorate photosynthetic capacity.Therefore,it is speculated that in arid or semi-arid areas,CO2 fertilization in protected agriculture or rising atmospheric CO2 concentration in future could meliorate plant water status,enhance drought resistance ability and improve water use efficiency to some extent,subsequently alleviate the negative effect of drought stresses.
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Claims 17
Claim · model-written summary
Drought reduced leaf net photosynthetic rate, transpiration rate and stomatal conductance.
- Taxon
- cucumber seedlings
Cucumis sativuse0 - Treatment
- Drought stressese0
- Outcome
- net photosynthetic rate,transpiration rate and stomatal conductancee0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Drought stresses remarkably reduced net photosynthetic rate,transpiration rate and stomatal conductance of leaves of cucumber seedlings.”
t0“Cucumber Seedlings”
Claim · model-written summary
Doubled CO2 increased net photosynthetic rate.
- Taxon
- cucumber seedlingsCucumis sativust0
- Treatment
- doubled CO2 concentratione0
- Outcome
- net photosynthetic ratee0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Under the condition of doubled CO2 concentration,net photosynthetic rate dramatically increased while transpiration rate and stomatal conductance decreased,thereby water use efficiency dramatically increased.”
t0“Cucumber Seedlings”
Claim · model-written summary
Doubled CO2 decreased transpiration rate and stomatal conductance.
- Taxon
- cucumber seedlingsCucumis sativust0
- Treatment
- doubled CO2 concentratione0
- Outcome
- transpiration rate and stomatal conductancee0
- Direction
- decreasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Under the condition of doubled CO2 concentration,net photosynthetic rate dramatically increased while transpiration rate and stomatal conductance decreased,thereby water use efficiency dramatically increased.”
t0“Cucumber Seedlings”
Claim · model-written summary
Doubled CO2 increased water use efficiency.
- Taxon
- cucumber seedlingsCucumis sativust0
- Treatment
- doubled CO2 concentratione0
- Outcome
- water use efficiencye0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Under the condition of doubled CO2 concentration,net photosynthetic rate dramatically increased while transpiration rate and stomatal conductance decreased,thereby water use efficiency dramatically increased.”
t0“Cucumber Seedlings”
Claim · model-written summary
CO2 and drought interacted significantly for four gas exchange traits.
- Taxon
- cucumber seedlingsCucumis sativust0
- Treatment
- doubled CO2 concentration and drought stresse0
- Outcome
- net photosynthetic rate,transpiration rate,water use efficiency as well as stomatal conductancee0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The interact effects of doubled CO2 concentration and drought stress on net photosynthetic rate,transpiration rate,water use efficiency as well as stomatal conductance were all significant(P0.01).”
t0“Cucumber Seedlings”
Claim · model-written summary
Drought reduced apparent quantum efficiency, maximum assimilation rate, and Rubisco carboxylation rate.
- Taxon
- cucumber seedlingsCucumis sativuse0
- Treatment
- Drought stressese0
- Outcome
- apparent quantum efficiency,maximum assimilation rate,maximum rate of carboxylation by Rubiscoe0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Drought stresses significantly reduced apparent quantum efficiency,maximum assimilation rate,maximum rate of carboxylation by Rubisco,PAR-saturated rate of electron transport,rate of triose phosphate utilization and light saturated points of leaves of cucumber seedlings,but enhanced light compensatory points.”
t0“Cucumber Seedlings”
Claim · model-written summary
Drought reduced electron transport rate, triose phosphate use and light saturation points.
- Taxon
- cucumber seedlingsCucumis sativuse0
- Treatment
- Drought stressese0
- Outcome
- PAR-saturated rate of electron transport,rate of triose phosphate utilization and light saturated pointse0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Drought stresses significantly reduced apparent quantum efficiency,maximum assimilation rate,maximum rate of carboxylation by Rubisco,PAR-saturated rate of electron transport,rate of triose phosphate utilization and light saturated points of leaves of cucumber seedlings,but enhanced light compensatory points.”
t0“Cucumber Seedlings”
Claim · model-written summary
Drought enhanced light compensation points.
- Taxon
- cucumber seedlingsCucumis sativuse0
- Treatment
- Drought stressese0
- Outcome
- light compensatory pointse0
- Direction
- enhancede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Drought stresses significantly reduced apparent quantum efficiency,maximum assimilation rate,maximum rate of carboxylation by Rubisco,PAR-saturated rate of electron transport,rate of triose phosphate utilization and light saturated points of leaves of cucumber seedlings,but enhanced light compensatory points.”
t0“Cucumber Seedlings”
Claim · model-written summary
Doubled CO2 improved apparent quantum efficiency and maximum assimilation under control and mild drought.
- Taxon
- cucumber seedlingsCucumis sativust0
- Treatment
- doubled CO2 concentratione0
- Outcome
- apparent quantum efficiency and maximum assimilation ratee0
- Direction
- improvede0
- Qualifier
- Under control and mild drought stress conditionse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Under control and mild drought stress conditions,doubled CO2 concentration dramatically improved apparent quantum efficiency and maximum assimilation rate,but there were no significant differences under severe drought stress.”
t0“Cucumber Seedlings”
Claim · model-written summary
Under severe drought, these two responses did not differ significantly with doubled CO2.
- Taxon
- cucumber seedlingsCucumis sativust0
- Treatment
- doubled CO2 concentratione0
- Outcome
- apparent quantum efficiency and maximum assimilation ratee0
- Qualifier
- under severe drought stresse0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Under control and mild drought stress conditions,doubled CO2 concentration dramatically improved apparent quantum efficiency and maximum assimilation rate,but there were no significant differences under severe drought stress.”
t0“Cucumber Seedlings”
Claim · model-written summary
Under control conditions, doubled CO2 enhanced Rubisco carboxylation, electron transport and triose phosphate use.
- Taxon
- cucumber seedlingsCucumis sativust0
- Treatment
- doubled CO2 concentratione0
- Outcome
- maximum rate of carboxylation by Rubisco,PAR-saturated rate of electron transport and rate of triose phosphate utilizatione0
- Direction
- enhancede0
- Qualifier
- Under control conditione0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Under control condition,doubled CO2 concentration dramatically enhanced maximum rate of carboxylation by Rubisco,PAR-saturated rate of electron transport and rate of triose phosphate utilization,but reduced CO2 compensatory points and respiration rate,there were no significant differences under drought stresses except CO2 compensatory points reduced by 4.9% under moderate drought stress.”
t0“Cucumber Seedlings”
Claim · model-written summary
Under control conditions, doubled CO2 reduced CO2 compensation points and respiration rate.
- Taxon
- cucumber seedlingsCucumis sativust0
- Treatment
- doubled CO2 concentratione0
- Outcome
- CO2 compensatory points and respiration ratee0
- Direction
- reducede0
- Qualifier
- Under control conditione0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Under control condition,doubled CO2 concentration dramatically enhanced maximum rate of carboxylation by Rubisco,PAR-saturated rate of electron transport and rate of triose phosphate utilization,but reduced CO2 compensatory points and respiration rate,there were no significant differences under drought stresses except CO2 compensatory points reduced by 4.9% under moderate drought stress.”
t0“Cucumber Seedlings”
Claim · model-written summary
Under drought these responses generally showed no significant differences.
- Taxon
- cucumber seedlingsCucumis sativust0
- Treatment
- doubled CO2 concentratione0
- Outcome
- maximum rate of carboxylation by Rubisco,PAR-saturated rate of electron transport and rate of triose phosphate utilizatione0
- Qualifier
- under drought stressese0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Under control condition,doubled CO2 concentration dramatically enhanced maximum rate of carboxylation by Rubisco,PAR-saturated rate of electron transport and rate of triose phosphate utilization,but reduced CO2 compensatory points and respiration rate,there were no significant differences under drought stresses except CO2 compensatory points reduced by 4.9% under moderate drought stress.”
t0“Cucumber Seedlings”
Claim · model-written summary
Under moderate drought, doubled CO2 reduced CO2 compensation points by 4.9%.
- Taxon
- cucumber seedlingsCucumis sativust0
- Treatment
- doubled CO2 concentratione0
- Outcome
- CO2 compensatory pointse0
- Direction
- reducede0
- Value
- 4.9%e0
- Qualifier
- under moderate drought stresse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Under control condition,doubled CO2 concentration dramatically enhanced maximum rate of carboxylation by Rubisco,PAR-saturated rate of electron transport and rate of triose phosphate utilization,but reduced CO2 compensatory points and respiration rate,there were no significant differences under drought stresses except CO2 compensatory points reduced by 4.9% under moderate drought stress.”
t0“Cucumber Seedlings”
Claim · model-written summary
Stomatal restriction accounted for reduced net photosynthesis under moderate drought.
- Taxon
- cucumber seedlingsCucumis sativust0
- Outcome
- decrease of net photosynthesise0
- Direction
- decreasee0
- Qualifier
- stoma restrictione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The decrease of net photosynthesis under moderate drought stress was due to stoma restriction,while it was due to stoma and non-stoma combined restriction under severe drought stress.”
t0“Cucumber Seedlings”
Claim · model-written summary
Stomatal and nonstomatal restriction accounted for reduced net photosynthesis under severe drought.
- Taxon
- cucumber seedlingsCucumis sativust0
- Outcome
- decrease of net photosynthesise0
- Direction
- decreasee0
- Qualifier
- stoma and non-stoma combined restrictione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The decrease of net photosynthesis under moderate drought stress was due to stoma restriction,while it was due to stoma and non-stoma combined restriction under severe drought stress.”
t0“Cucumber Seedlings”
Claim · model-written summary
Drought reduced photosynthetic electron transport and photophosphorylation capacity.
- Taxon
- cucumber seedlingsCucumis sativuse0
- Treatment
- Drought stressese0
- Outcome
- photosynthetic electron transport and photophosphorylation capacitye0
- Direction
- declinee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Drought stresses resulted in dramatic decline of photosynthetic electron transport and photophosphorylation capacity of cucumber seedlings.”
t0“Cucumber Seedlings”
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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.