Abstract
The long‐term interaction between elevated CO 2 and soil water deficit was analysed in N 2 ‐fixing alfalfa plants in order to assess the possible drought tolerance effect of CO 2 . Elevated CO 2 could delay the onset of drought stress by decreasing transpiration rates, but this effect was avoided by subjecting plants to the same soil water content. Nodulated alfalfa plants subjected to ambient (400 μmol mol −1 ) or elevated (700 μmol mol −1 ) CO 2 were either well watered or partially watered by restricting water to obtain 30% of the water content at field capacity (ampproximately 0.55 g water cm −3 ). The negative effects of soil water deficit on plant growth were counterbalanced by elevated CO 2 . In droughted plants, elevated CO 2 stimulated carbon fixation and, as a result, biomass production was even greater than in well‐watered plants grown in ambient CO 2 . Below‐ground production was preferentially stimulated by elevated CO 2 in droughted plants, increasing nodule biomass production and the availability of photosynthates to the nodules. As a result, total nitrogen content in droughted plants was higher than in well‐watered plants grown in ambient CO 2 . The beneficial effect of elevated CO 2 was not correlated with a better plant water status. It is concluded that elevated CO 2 enhances growth of droughted plants by stimulating carbon fixation, preferentially increasing the availability of photosynthates to below‐ground production (roots and nodules) without improving water status. This means that elevated CO 2 enhances the ability to produce more biomass in N 2 ‐fixing alfalfa under given soil water stress, improving drought tolerance.
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Claims 9
Claim · model-written summary
Elevated CO2 counterbalanced water deficit effects on alfalfa growth.
- Taxon
- alfalfa
Medicago sativae1 - Treatment
- elevated CO 2e0
- Outcome
- plant growthe0
- Direction
- counterbalancede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The negative effects of soil water deficit on plant growth were counterbalanced by elevated CO 2”
e1“N 2 ‐fixing alfalfa plants”
Claim · model-written summary
Elevated CO2 stimulated carbon fixation in droughted alfalfa.
- Taxon
- alfalfaMedicago sativae1
- Treatment
- elevated CO 2e0
- Outcome
- carbon fixatione0
- Direction
- stimulatede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In droughted plants, elevated CO 2 stimulated carbon fixation”
e1“N 2 ‐fixing alfalfa plants”
Claim · model-written summary
Droughted alfalfa under elevated CO2 produced more biomass than well-watered plants at ambient CO2.
- Taxon
- alfalfaMedicago sativae2
- Treatment
- elevated CO 2e1
- Outcome
- biomass productione0
- Direction
- greatere0
- Comparator
- well‐watered plants grown in ambient CO 2e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“biomass production was even greater than in well‐watered plants grown in ambient CO 2”
e1“In droughted plants, elevated CO 2 stimulated carbon fixation”
e2“N 2 ‐fixing alfalfa plants”
Claim · model-written summary
Elevated CO2 preferentially stimulated belowground production in droughted alfalfa.
- Taxon
- alfalfaMedicago sativae1
- Treatment
- elevated CO 2e0
- Outcome
- Below‐ground productione0
- Direction
- stimulatede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Below‐ground production was preferentially stimulated by elevated CO 2 in droughted plants”
e1“N 2 ‐fixing alfalfa plants”
Claim · model-written summary
Elevated CO2 increased nodule biomass in droughted alfalfa.
- Taxon
- alfalfaMedicago sativae2
- Organ / stage
- nodulese0
- Treatment
- elevated CO 2e1
- Outcome
- nodule biomass productione0
- Direction
- increasinge0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“increasing nodule biomass production and the availability of photosynthates to the nodules”
e1“stimulated by elevated CO 2 in droughted plants”
e2“N 2 ‐fixing alfalfa plants”
Claim · model-written summary
Elevated CO2 increased photosynthate availability to alfalfa nodules.
- Taxon
- alfalfaMedicago sativae2
- Treatment
- elevated CO 2e1
- Outcome
- availability of photosynthates to the nodulese0
- Direction
- increasinge0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“increasing nodule biomass production and the availability of photosynthates to the nodules”
e1“stimulated by elevated CO 2 in droughted plants”
e2“N 2 ‐fixing alfalfa plants”
Claim · model-written summary
Total nitrogen content in droughted alfalfa was higher than in well-watered plants at ambient CO2.
- Taxon
- alfalfaMedicago sativae1
- Treatment
- droughted plantse0
- Outcome
- total nitrogen contente0
- Direction
- highere0
- Comparator
- well‐watered plants grown in ambient CO 2e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“total nitrogen content in droughted plants was higher than in well‐watered plants grown in ambient CO 2”
e1“N 2 ‐fixing alfalfa plants”
Claim · model-written summary
Elevated CO2 benefit was not correlated with better alfalfa water status.
- Taxon
- alfalfaMedicago sativae1
- Treatment
- elevated CO 2e0
- Outcome
- plant water statuse0
- Direction
- not correlatede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The beneficial effect of elevated CO 2 was not correlated with a better plant water status”
e1“N 2 ‐fixing alfalfa plants”
Claim · model-written summary
Authors conclude elevated CO2 improves alfalfa drought tolerance through carbon fixation and belowground allocation.
- Taxon
- alfalfaMedicago sativae1
- Treatment
- elevated CO 2e0
- Outcome
- growth of droughted plantse0
- Qualifier
- stimulating carbon fixatione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“elevated CO 2 enhances growth of droughted plants by stimulating carbon fixation, preferentially increasing the availability of photosynthates to below‐ground production (roots and nodules) without improving water status”
e1“N 2 ‐fixing alfalfa plants”
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