Abstract
The effects of elevated CO2 (750 ppm vs. 390 ppm) were evaluated on nitrogen (N) acquisition and assimilation by three Medicago truncatula genotypes, including two N-fixing-deficient mutants (dnf1-1 and dnf1-2) and their wild-type (Jemalong). The proportion of N acquisition from atmosphere and soil were quantified by (15)N stable isotope, and N transportation and assimilation-related genes and enzymes were determined by qPCR and biochemical analysis. Elevated CO2 decreased nitrate uptake from soil in all three plant genotypes by down-regulating nitrate reductase (NR), nitrate transporter NRT1.1 and NR activity. Jemalong plant, however, produced more nodules, up-regulated N-fixation-related genes and enhanced percentage of N derived from fixation (%Ndf) to increase foliar N concentration and N content in whole plant (Ntotal Yield) to satisfy the requirement of larger biomass under elevated CO2. In contrast, both dnf1 mutants deficient in N fixation consequently decreased activity of glutamine synthetase/glutamate synthase (GS/GOGAT) and N concentration under elevated CO2. Our results suggest that elevated CO2 is likely to modify N acquisition of M. truncatula by simultaneously increasing N fixation and reducing nitrate uptake from soil. We propose that elevated CO2 causes legumes to rely more on N fixation than on N uptake from soil to satisfy N requirements.
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Claims 12
Claim · model-written summary
Elevated CO2 reduced nitrate uptake from soil in all three Medicago truncatula genotypes.
- Taxon
- Medicago truncatula
Medicago truncatulat0 - Treatment
- Elevated CO2e0
- Outcome
- nitrate uptake from soile0
- Direction
- decreasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Elevated CO2 decreased nitrate uptake from soil in all three plant genotypes”
t0“Medicago truncatula”
Claim · model-written summary
Elevated CO2 down-regulated nitrate reductase and nitrate transporter NRT1.1 in the three genotypes.
- Taxon
- Medicago truncatulaMedicago truncatulat0
- Treatment
- Elevated CO2e0
- Gene
- nitrate reductase (NR), nitrate transporter NRT1.1e0
- Outcome
- nitrate reductase (NR), nitrate transporter NRT1.1e0
- Direction
- down-regulatinge0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Elevated CO2 decreased nitrate uptake from soil in all three plant genotypes by down-regulating nitrate reductase (NR), nitrate transporter NRT1.1 and NR activity”
t0“Medicago truncatula”
Claim · model-written summary
Elevated CO2 reduced nitrate reductase activity in all three genotypes.
- Taxon
- Medicago truncatulaMedicago truncatulat0
- Treatment
- Elevated CO2e0
- Outcome
- NR activitye0
- Direction
- down-regulatinge0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Elevated CO2 decreased nitrate uptake from soil in all three plant genotypes by down-regulating nitrate reductase (NR), nitrate transporter NRT1.1 and NR activity”
t0“Medicago truncatula”
Claim · model-written summary
Jemalong produced more nodules under elevated CO2.
- Taxon
- Medicago truncatulaMedicago truncatulat0
- Material
- Jemalonge0
- Treatment
- elevated CO2e1
- Outcome
- nodulese0
- Direction
- moree0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Jemalong plant, however, produced more nodules”
e1“larger biomass under elevated CO2”
t0“Medicago truncatula”
Claim · model-written summary
Jemalong up-regulated nitrogen fixation genes under elevated CO2.
- Taxon
- Medicago truncatulaMedicago truncatulat0
- Material
- Jemalonge0
- Treatment
- elevated CO2e1
- Gene
- N-fixation-related genese0
- Outcome
- N-fixation-related genese0
- Direction
- up-regulatede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Jemalong plant, however, produced more nodules, up-regulated N-fixation-related genes”
e1“larger biomass under elevated CO2”
t0“Medicago truncatula”
Claim · model-written summary
Jemalong increased its percentage of nitrogen derived from fixation under elevated CO2.
- Taxon
- Medicago truncatulaMedicago truncatulat0
- Material
- Jemalonge2
- Treatment
- elevated CO2e1
- Outcome
- percentage of N derived from fixation (%Ndf)e0
- Direction
- enhancede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“enhanced percentage of N derived from fixation (%Ndf)”
e1“larger biomass under elevated CO2”
e2“Jemalong plant”
t0“Medicago truncatula”
Claim · model-written summary
Jemalong increased foliar nitrogen concentration under elevated CO2.
- Taxon
- Medicago truncatulaMedicago truncatulat0
- Material
- Jemalonge1
- Treatment
- elevated CO2e2
- Outcome
- foliar N concentratione0
- Direction
- increasee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“increase foliar N concentration and N content in whole plant (Ntotal Yield)”
e1“Jemalong plant”
e2“larger biomass under elevated CO2”
t0“Medicago truncatula”
Claim · model-written summary
Jemalong increased whole-plant nitrogen content under elevated CO2.
- Taxon
- Medicago truncatulaMedicago truncatulat0
- Material
- Jemalonge1
- Treatment
- elevated CO2e2
- Outcome
- N content in whole plant (Ntotal Yield)e0
- Direction
- increasee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“increase foliar N concentration and N content in whole plant (Ntotal Yield)”
e1“Jemalong plant”
e2“larger biomass under elevated CO2”
t0“Medicago truncatula”
Claim · model-written summary
Jemalong had larger biomass under elevated CO2.
- Taxon
- Medicago truncatulaMedicago truncatulat0
- Material
- Jemalonge1
- Treatment
- elevated CO2e0
- Outcome
- biomasse0
- Direction
- largere0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“larger biomass under elevated CO2”
e1“Jemalong plant”
t0“Medicago truncatula”
Claim · model-written summary
The two dnf1 mutants had decreased GS/GOGAT activity under elevated CO2.
- Taxon
- Medicago truncatulaMedicago truncatulat0
- Material
- dnf1 mutantse0
- Treatment
- elevated CO2e0
- Outcome
- activity of glutamine synthetase/glutamate synthase (GS/GOGAT)e0
- Direction
- decreasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“both dnf1 mutants deficient in N fixation consequently decreased activity of glutamine synthetase/glutamate synthase (GS/GOGAT) and N concentration under elevated CO2”
t0“Medicago truncatula”
Claim · model-written summary
The two dnf1 mutants had decreased nitrogen concentration under elevated CO2.
- Taxon
- Medicago truncatulaMedicago truncatulat0
- Material
- dnf1 mutantse0
- Treatment
- elevated CO2e0
- Outcome
- N concentratione0
- Direction
- decreasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“both dnf1 mutants deficient in N fixation consequently decreased activity of glutamine synthetase/glutamate synthase (GS/GOGAT) and N concentration under elevated CO2”
t0“Medicago truncatula”
Claim · model-written summary
The authors propose that elevated CO2 causes legumes to rely more on nitrogen fixation than soil uptake.
Verbatim
e0“elevated CO2 causes legumes to rely more on N fixation than on N uptake from soil to satisfy N requirements”
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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.