Abstract
Drought stress severely limits crop growth and yield. With the atmospheric CO2 constantly increasing, plants will be affected by multiple effects of drought and increased CO2 in the future. Abscisic acid (ABA) plays vital roles in plant stress tolerance, especially drought stress. However, little is known about the effects of elevated CO2 concentration (e[CO2]) and exogenous ABA in cucumber (Cucumis sativus L.) response to drought stress. In the present study, we investigated the effects of e[CO2] and exogenous ABA on the drought tolerance of cucumber seedlings under the simulated drought stress induced by 5% polyethylene glycol 6000. The experiment was a split-plot design, in which the main factor was CO2 concentrations; atmospheric and elevated CO2 concentrations (~400 and 800 ± 40 μmol mol−1, respectively). The subplot factor was the combinations of exogenous ABA and its synthesis inhibitor sodium tungstate (Na2WO4); deionized water (control), 20 μM ABA, 2 mM Na2WO4, and 2 mM Na2WO4 + 20 μM ABA, which were applied to plant leaves. The results showed that compared with exogenous ABA application only, e[CO2] combined with exogenous ABA significantly increased the biomass, chlorophyll content, and net photosynthetic rate (Pn) of cucumber seedlings under drought stress. Meanwhile, e[CO2] and exogenous ABA were more efficient in reducing the contents of reactive oxygen species and malondialdehyde, promoting the accumulation of proline, soluble sugar, soluble protein, free amino acid, ascorbic acid, and glutathione. The ratios of ascorbic acid/dehydroascorbic acid (ASA/DHA), glutathione/oxidized glutathione (GSH/GSSG), as well as the activities of antioxidant enzymes were increased. In conclusion, e[CO2] and exogenous ABA synergistically alleviated oxidative damage of drought stress on cucumber seedlings by increasing antioxidant enzyme activities and accelerating the ASA–GSH cycle in cucumber seedlings, which in turn improved the drought tolerance of cucumber seedlings, and provided theoretical and practical support for further studies on the alleviation of drought stress in protected horticulture.
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Claims 6
Claim · model-written summary
Elevated CO2 with ABA increased cucumber biomass, chlorophyll content and photosynthetic rate relative to ABA alone.
- Taxon
- cucumber
Cucumis sativuse0 - Treatment
- e[CO2] combined with exogenous ABAe0
- Outcome
- biomass, chlorophyll content, and net photosynthetic rate (Pn)e0
- Direction
- increasede0
- Qualifier
- under drought stresse0
- Comparator
- exogenous ABA application onlye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“compared with exogenous ABA application only, e[CO2] combined with exogenous ABA significantly increased the biomass, chlorophyll content, and net photosynthetic rate (Pn) of cucumber seedlings under drought stress”
Claim · model-written summary
Elevated CO2 with ABA reduced reactive oxygen species and malondialdehyde.
- Taxon
- CucumberCucumis sativust0
- Treatment
- e[CO2] and exogenous ABAe0
- Outcome
- contents of reactive oxygen species and malondialdehydee0
- Direction
- reducinge0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“e[CO2] and exogenous ABA were more efficient in reducing the contents of reactive oxygen species and malondialdehyde”
t0“Cucumber Seedlings”
Claim · model-written summary
Elevated CO2 with ABA promoted proline, soluble sugar and soluble protein accumulation.
- Taxon
- CucumberCucumis sativust0
- Treatment
- e[CO2] and exogenous ABAe0
- Outcome
- accumulation of proline, soluble sugar, soluble proteine0
- Direction
- promotinge0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“e[CO2] and exogenous ABA were more efficient in reducing the contents of reactive oxygen species and malondialdehyde, promoting the accumulation of proline, soluble sugar, soluble protein, free amino acid, ascorbic acid, and glutathione”
t0“Cucumber Seedlings”
Claim · model-written summary
Elevated CO2 with ABA promoted free amino acid, ascorbic acid and glutathione accumulation.
- Taxon
- CucumberCucumis sativust0
- Treatment
- e[CO2] and exogenous ABAe1
- Outcome
- free amino acid, ascorbic acid, and glutathionee0
- Direction
- promotinge0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“promoting the accumulation of proline, soluble sugar, soluble protein, free amino acid, ascorbic acid, and glutathione”
e1“e[CO2] and exogenous ABA were more efficient”
t0“Cucumber Seedlings”
Claim · model-written summary
The ASA/DHA and GSH/GSSG ratios and antioxidant enzyme activities increased.
- Taxon
- CucumberCucumis sativust0
- Treatment
- e[CO2] and exogenous ABAe1
- Outcome
- ratios of ascorbic acid/dehydroascorbic acid (ASA/DHA), glutathione/oxidized glutathione (GSH/GSSG), as well as the activities of antioxidant enzymese0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The ratios of ascorbic acid/dehydroascorbic acid (ASA/DHA), glutathione/oxidized glutathione (GSH/GSSG), as well as the activities of antioxidant enzymes were increased”
e1“e[CO2] and exogenous ABA were more efficient”
t0“Cucumber Seedlings”
Claim · model-written summary
Elevated CO2 and ABA synergistically alleviated oxidative damage and improved drought tolerance through antioxidant enzyme activities and the ASA–GSH cycle.
- Taxon
- cucumberCucumis sativuse0
- Treatment
- e[CO2] and exogenous ABAe0
- Outcome
- drought tolerancee0
- Qualifier
- increasing antioxidant enzyme activities and accelerating the ASA–GSH cyclee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“e[CO2] and exogenous ABA synergistically alleviated oxidative damage of drought stress on cucumber seedlings by increasing antioxidant enzyme activities and accelerating the ASA–GSH cycle in cucumber seedlings, which in turn improved the drought tolerance of cucumber seedlings”
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8 of 10 groups shown: named compounds and organisms first, then groups whose results differ (checked claim by claim), then those with positive and negative results, then the smaller groups.
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.