Abstract
BACKGROUND AND AIMS: Additional carbohydrate supply resulting from enhanced photosynthesis under predicted future elevated CO2 is likely to increase symbiotic nitrogen (N) fixation in legumes. This study examined the interactive effects of atmospheric CO2 and nitrate (NO3(-)) concentration on the growth, nodulation and N fixation of field pea (Pisum sativum) in a semi-arid cropping system. METHODS: Field pea was grown for 15 weeks in a Vertosol containing 5, 25, 50 or 90 mg NO3(-)-N kg(-1) under either ambient CO2 (aCO2; 390 ppm) or elevated CO2 (eCO2; 550 ppm) using free-air CO2 enrichment (SoilFACE). KEY RESULTS: Under aCO2, field pea biomass was significantly lower at 5 mg NO3(-)-N kg(-1) than at 90 mg NO3(-)-N kg(-1) soil. However, increasing the soil N level significantly reduced nodulation of lateral roots but not the primary root, and nodules were significantly smaller, with 85% less nodule mass in the 90 NO3(-)-N kg(-1) than in the 5 mg NO3(-)-N kg(-1) treatment, highlighting the inhibitory effects of NO3(-). Field pea grown under eCO2 had greater biomass (approx. 30%) than those grown under aCO2, and was not affected by N level. Overall, the inhibitory effects of NO3(-) on nodulation and nodule mass appeared to be reduced under eCO2 compared with aCO2, although the effects of CO2 on root growth were not significant. CONCLUSIONS: Elevated CO2 alleviated the inhibitory effect of soil NO3(-) on nodulation and N2 fixation and is likely to lead to greater total N content of field pea growing under future elevated CO2 environments.
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Claims 11
Claim · model-written summary
Under ambient CO2, pea biomass was lower at 5 than 90 mg nitrate nitrogen per kg soil.
Verbatim
e0“Under aCO2, field pea biomass was significantly lower at 5 mg NO3(-)-N kg(-1) than at 90 mg NO3(-)-N kg(-1) soil.”
Claim · model-written summary
Increasing soil nitrogen significantly reduced lateral root nodulation.
- Taxon
- Pisum sativum
Lathyrus oleraceust0 - Treatment
- increasing the soil N levele0
- Outcome
- nodulation of lateral rootse0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“increasing the soil N level significantly reduced nodulation of lateral roots but not the primary root”
t0“Pisum sativum”
Claim · model-written summary
Increasing soil nitrogen did not reduce primary root nodulation.
- Taxon
- Pisum sativumLathyrus oleraceust0
- Treatment
- increasing the soil N levele0
- Outcome
- nodulation of lateral roots but not the primary roote0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“increasing the soil N level significantly reduced nodulation of lateral roots but not the primary root”
t0“Pisum sativum”
Claim · model-written summary
Higher nitrate produced smaller nodules.
- Taxon
- Pisum sativumLathyrus oleraceust0
- Treatment
- 90 NO3(-)-N kg(-1)e0
- Outcome
- nodulese0
- Direction
- smallere0
- Comparator
- 5 mg NO3(-)-N kg(-1)e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“nodules were significantly smaller, with 85% less nodule mass in the 90 NO3(-)-N kg(-1) than in the 5 mg NO3(-)-N kg(-1) treatment”
t0“Pisum sativum”
Claim · model-written summary
Nodule mass was 85% lower at the higher nitrate rate.
- Taxon
- Pisum sativumLathyrus oleraceust0
- Treatment
- 90 NO3(-)-N kg(-1)e0
- Outcome
- nodule masse0
- Direction
- lesse0
- Value
- 85%e0
- Comparator
- 5 mg NO3(-)-N kg(-1)e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“85% less nodule mass in the 90 NO3(-)-N kg(-1) than in the 5 mg NO3(-)-N kg(-1) treatment”
t0“Pisum sativum”
Claim · model-written summary
Elevated CO2 raised pea biomass by approximately 30% versus ambient CO2.
Verbatim
e0“Field pea grown under eCO2 had greater biomass (approx. 30%) than those grown under aCO2, and was not affected by N level.”
Claim · model-written summary
Pea biomass under elevated CO2 was unaffected by nitrogen level.
Not reportedComparatorDirection
Verbatim
e0“Field pea grown under eCO2 had greater biomass (approx. 30%) than those grown under aCO2, and was not affected by N level.”
Claim · model-written summary
Elevated CO2 appeared to reduce nitrate inhibition of nodulation and nodule mass.
- Taxon
- Pisum sativumLathyrus oleraceust0
- Treatment
- eCO2e0
- Outcome
- inhibitory effects of NO3(-) on nodulation and nodule masse0
- Direction
- reducede0
- Comparator
- aCO2e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the inhibitory effects of NO3(-) on nodulation and nodule mass appeared to be reduced under eCO2 compared with aCO2”
t0“Pisum sativum”
Claim · model-written summary
CO2 effects on root growth were not significant.
- Taxon
- Pisum sativumLathyrus oleraceust0
- Treatment
- CO2e0
- Outcome
- root growthe0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the effects of CO2 on root growth were not significant”
t0“Pisum sativum”
Claim · model-written summary
Elevated CO2 alleviated nitrate inhibition of nitrogen fixation.
- Taxon
- Pisum sativumLathyrus oleraceust0
- Treatment
- Elevated CO2e0
- Outcome
- N2 fixatione0
- Direction
- alleviatede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Elevated CO2 alleviated the inhibitory effect of soil NO3(-) on nodulation and N2 fixation”
t0“Pisum sativum”
Claim · model-written summary
Elevated CO2 is expected to increase total nitrogen content in future pea environments.
Verbatim
e0“is likely to lead to greater total N content of field pea growing under future elevated CO2 environments.”
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