Abstract
ABSTRACT Elevated atmospheric CO 2 and ozone (O 3 ) may affect productivity of legumes in part by altering symbiotic N 2 fixation. To investigate this possibility, measurements of plant biomass, N levels and natural 15 N abundance (δ 15 N) were used to examine the effects of elevated CO 2 and O 3 on N acquisition in field‐grown peanut ( Arachis hypogaea L.) using open‐top chambers. Seasonal 12‐h daily average CO 2 treatment concentrations were 376, 550, and 730 μmol mol −1 Carbon dioxide treatments were applied in reciprocal combinations with seasonal 12‐h daily average O 3 concentrations of 21, 49, and 79 nmol mol −1 At mid‐vegetative growth, elevated CO 2 significantly reduced leaf N concentrations by up to 44%, but not δ 15 N values. Elevated O 3 did not significantly affect N concentrations or δ 15 N values. At harvest, plant N concentrations were similar among treatments except for a 14% reduction in the highest‐level CO 2 –O 3 treatment. Plant N accumulation varied in proportion with treatment effects on biomass production, which was increased with elevated CO 2 when averaged over the O 3 treatments and suppressed by high‐level O 3 at ambient CO 2 Elevated CO 2 reduced plant δ 15 N values in low‐ and mid‐level O 3 treatments while mid‐ and high‐level O 3 increased them at ambient CO 2 The changes in δ 15 N values suggested that N 2 fixation activity was stimulated with elevated CO 2 and inhibited by elevated O 3 Elevated CO 2 ameliorated detrimental O 3 effects to varying extents depending on the concentrations of the two gases. These results indicated that interactions between CO 2 and O 3 on plant physiology can alter N acquisition processes, with impacts on peanut productivity likely dependent in part on these changes.
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Claims 12
Claim · model-written summary
Elevated CO2 reduced midvegetative leaf N concentration by up to 44%.
- Taxon
- Peanut
Arachis hypogaeat0 - Treatment
- elevated CO 2e0
- Outcome
- leaf N concentrationse0
- Direction
- reducede0
- Value
- 44%e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Peanut”
e0“elevated CO 2 significantly reduced leaf N concentrations by up to 44%”
Claim · model-written summary
Elevated CO2 did not significantly alter midvegetative δ15N.
- Taxon
- PeanutArachis hypogaeat0
- Treatment
- elevated CO 2e0
- Outcome
- δ 15 N valuese0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Peanut”
e0“elevated CO 2 significantly reduced leaf N concentrations by up to 44%, but not δ 15 N values”
Claim · model-written summary
Elevated O3 did not significantly affect N concentrations or δ15N.
- Taxon
- PeanutArachis hypogaeat0
- Treatment
- Elevated O 3e0
- Outcome
- N concentrations or δ 15 N valuese0
- Direction
- did not significantly affecte0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Peanut”
e0“Elevated O 3 did not significantly affect N concentrations or δ 15 N values”
Claim · model-written summary
Highest CO2–O3 treatment reduced harvest plant N concentration by 14%.
- Taxon
- PeanutArachis hypogaeat0
- Treatment
- highest‐level CO 2 –O 3 treatmente0
- Outcome
- plant N concentrationse1
- Direction
- reductione0
- Value
- 14%e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Peanut”
e0“a 14% reduction in the highest‐level CO 2 –O 3 treatment”
e1“At harvest, plant N concentrations were similar among treatments”
Claim · model-written summary
Plant N accumulation varied proportionally with biomass production.
- Taxon
- PeanutArachis hypogaeat0
- Treatment
- treatment effects on biomass productione0
- Outcome
- Plant N accumulatione0
- Direction
- varied in proportione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Peanut”
e0“Plant N accumulation varied in proportion with treatment effects on biomass production”
Claim · model-written summary
Elevated CO2 increased biomass averaged across O3 treatments.
- Taxon
- PeanutArachis hypogaeat0
- Treatment
- elevated CO 2e0
- Outcome
- biomass productione0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Peanut”
e0“biomass production, which was increased with elevated CO 2 when averaged over the O 3 treatments”
Claim · model-written summary
High O3 suppressed biomass at ambient CO2.
- Taxon
- PeanutArachis hypogaeat0
- Treatment
- high‐level O 3e0
- Outcome
- biomass productione1
- Direction
- suppressede0
- Qualifier
- ambient CO 2e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Peanut”
e0“suppressed by high‐level O 3 at ambient CO 2”
e1“Plant N accumulation varied in proportion with treatment effects on biomass production”
Claim · model-written summary
Elevated CO2 reduced δ15N at low and mid O3.
- Taxon
- PeanutArachis hypogaeat0
- Treatment
- Elevated CO 2e0
- Outcome
- plant δ 15 N valuese0
- Direction
- reducede0
- Qualifier
- low‐ and mid‐level O 3 treatmentse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Peanut”
e0“Elevated CO 2 reduced plant δ 15 N values in low‐ and mid‐level O 3 treatments”
Claim · model-written summary
Mid and high O3 increased δ15N at ambient CO2.
- Taxon
- PeanutArachis hypogaeat0
- Treatment
- mid‐ and high‐level O 3e0
- Outcome
- plant δ 15 N valuese1
- Direction
- increasede0
- Qualifier
- ambient CO 2e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Peanut”
e0“mid‐ and high‐level O 3 increased them at ambient CO 2”
e1“Elevated CO 2 reduced plant δ 15 N values”
Claim · model-written summary
δ15N changes suggested CO2 stimulates N2 fixation.
- Taxon
- PeanutArachis hypogaeat0
- Treatment
- elevated CO 2e0
- Outcome
- N 2 fixation activitye0
- Direction
- stimulatede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Peanut”
e0“The changes in δ 15 N values suggested that N 2 fixation activity was stimulated with elevated CO 2”
Claim · model-written summary
δ15N changes suggested O3 inhibits N2 fixation.
- Taxon
- PeanutArachis hypogaeat0
- Treatment
- elevated O 3e0
- Outcome
- N 2 fixation activitye0
- Direction
- inhibitede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Peanut”
e0“N 2 fixation activity was stimulated with elevated CO 2 and inhibited by elevated O 3”
Claim · model-written summary
Elevated CO2 ameliorated detrimental O3 effects to varying degrees.
- Taxon
- PeanutArachis hypogaeat0
- Treatment
- Elevated CO 2e0
- Outcome
- detrimental O 3 effectse0
- Direction
- amelioratede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Peanut”
e0“Elevated CO 2 ameliorated detrimental O 3 effects to varying extents depending on the concentrations of the two gases”
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