Abstract
Pigeon peas [Cajanus cajan (L.) Millsp.] were grown in soil columns containing (15)N-enriched organic matter. Seasonal N(2) fixation activity was determined by periodically assaying plants for reduction of C(2)H(2). N(2) fixation rose sharply from the first assay period at 51 days after planting to a peak of activity between floral initiation and fruit set. N(2) fixation (acetylene reduction) activity dropped concomitantly with pod maturation but recovered after pod harvests. Analysis of (15)N content of plant shoots revealed that approximately 91 to 94% of plant N was derived from N(2) fixation. The effect of inoculation with hydrogenase-positive and hydrogenase-negative rhizobia was examined. Pigeon peas inoculated with strain P132 (hydrogenase-positive) yielded significantly more total shoot N than other inoculated or uninoculated treatments. However, two other hydrogenase-positive strains did not yield significantly more total shoot N than a hydrogenase-negative strain. The extent of nodulation by inoculum strains compared to indigenous rhizobia was determined by typing nodules according to intrinsic antibiotic resistance of the inoculum strains. The inoculum strains were detected in almost all typed nodules of inoculated plants.Gas samples were taken from soil columns several times during the growth cycle of the plants. H(2) was never detected, even in columns containing pigeon peas inoculated with hydrogenase-negative rhizobia. This was attributed to H(2) consumption by soil bacteria. Estimation of N(2) fixation by acetylene reduction activity was closest to the direct (15)N method when ethylene concentrations in the gas headspace (between the column lid and soil surface) were extrapolated to include the soil pore space as opposed solely to measurement in the headspace. There was an 8-fold difference between the two acetylene reduction assay methods of estimation. Based on a planting density of 15,000 plants per hectare, the direct (15)N fixation rates ranged from 67 (noninoculated) to 134 kilograms per hectare, while grain yields ranged from 540 to 825 kilograms per hectare. Grain yields were not increased with N fertilizer.
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Claims 14
Claim · model-written summary
N2 fixation rose sharply from the first assay at 51 days after planting to a peak of activity between floral initiation and fruit set in pigeon pea.
- Taxon
- Cajanus cajan
Cajanus cajant0 - Outcome
- N(2) fixatione1
- Direction
- rose sharplye1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Cajanus cajan”
e1“N(2) fixation rose sharply from the first assay period at 51 days after planting to a peak of activity between floral initiation and fruit set”
Claim · model-written summary
N2 fixation (acetylene reduction) activity dropped concomitantly with pod maturation.
- Taxon
- Cajanus cajanCajanus cajant0
- Outcome
- N(2) fixation (acetylene reduction) activitye1
- Direction
- droppede1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Cajanus cajan”
e1“N(2) fixation (acetylene reduction) activity dropped concomitantly with pod maturation but recovered after pod harvests”
Claim · model-written summary
N2 fixation (acetylene reduction) activity recovered after pod harvests.
- Taxon
- Cajanus cajanCajanus cajant0
- Outcome
- N(2) fixation (acetylene reduction) activitye1
- Direction
- recoverede1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Cajanus cajan”
e1“N(2) fixation (acetylene reduction) activity dropped concomitantly with pod maturation but recovered after pod harvests”
Claim · model-written summary
Approximately 91 to 94% of plant N was derived from N2 fixation, from the (15)N content of shoots.
- Taxon
- Cajanus cajanCajanus cajant0
- Organ / stage
- plant shootse1
- Outcome
- plant N was derived from N(2) fixatione1
- Value
- 91 to 94%e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Cajanus cajan”
e1“Analysis of (15)N content of plant shoots revealed that approximately 91 to 94% of plant N was derived from N(2) fixation”
Claim · model-written summary
Pigeon peas inoculated with the hydrogenase-positive strain P132 yielded significantly more total shoot N than other inoculated or uninoculated treatments.
- Taxon
- Pigeon peasCajanus cajane1
- Treatment
- inoculated with strain P132 (hydrogenase-positive)e1
- Interactor
- strain P132e1symbiont
- Outcome
- total shoot Ne1
- Direction
- moree1
- Comparator
- other inoculated or uninoculated treatmentse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“Pigeon peas inoculated with strain P132 (hydrogenase-positive) yielded significantly more total shoot N than other inoculated or uninoculated treatments”
Claim · model-written summary
Two other hydrogenase-positive strains did not yield significantly more total shoot N than a hydrogenase-negative strain.
- Taxon
- Cajanus cajanCajanus cajant0
- Treatment
- two other hydrogenase-positive strainse1
- Interactor
- hydrogenase-positive strainse1symbiont
- Outcome
- total shoot Ne1
- Direction
- no_changeinferrede1
- Comparator
- a hydrogenase-negative straine1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Cajanus cajan”
e1“two other hydrogenase-positive strains did not yield significantly more total shoot N than a hydrogenase-negative strain”
Claim · model-written summary
The inoculum strains were detected in almost all typed nodules of inoculated plants.
- Taxon
- Cajanus cajanCajanus cajant0
- Organ / stage
- nodulese1
- Interactor
- inoculum strainse1symbiont
- Outcome
- inoculum strains were detected in almost all typed nodulese1
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Cajanus cajan”
e1“The inoculum strains were detected in almost all typed nodules of inoculated plants”
Claim · model-written summary
H2 was never detected in soil column gas samples, even in columns with pigeon peas inoculated with hydrogenase-negative rhizobia.
- Taxon
- pigeon peasCajanus cajane1
- Interactor
- hydrogenase-negative rhizobiae1symbiont
- Outcome
- H(2) was never detectede1
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“H(2) was never detected, even in columns containing pigeon peas inoculated with hydrogenase-negative rhizobia”
Claim · model-written summary
The authors attribute the absence of H2 to H2 consumption by soil bacteria.
- Taxon
- Cajanus cajanCajanus cajant0
- Interactor
- soil bacteriae1other
- Outcome
- H(2) consumptione1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Cajanus cajan”
e1“This was attributed to H(2) consumption by soil bacteria”
Claim · model-written summary
Estimation of N2 fixation by acetylene reduction was closest to the direct (15)N method when ethylene concentrations were extrapolated to include the soil pore space rather than only the headspace.
- Taxon
- Cajanus cajanCajanus cajant0
- Outcome
- Estimation of N(2) fixation by acetylene reduction activitye1
- Direction
- closeste1
- Comparator
- direct (15)N methode1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Cajanus cajan”
e1“Estimation of N(2) fixation by acetylene reduction activity was closest to the direct (15)N method when ethylene concentrations in the gas headspace (between the column lid and soil surface) were extrapolated to include the soil pore space as opposed solely to measurement in the headspace”
Claim · model-written summary
There was an 8-fold difference between the two acetylene reduction assay methods of estimation.
- Taxon
- Cajanus cajanCajanus cajant0
- Outcome
- difference between the two acetylene reduction assay methods of estimatione1
- Value
- 8-folde1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Cajanus cajan”
e1“There was an 8-fold difference between the two acetylene reduction assay methods of estimation”
Claim · model-written summary
Direct (15)N fixation rates ranged from 67 kg per hectare (noninoculated) to 134 kg per hectare.
- Taxon
- Cajanus cajanCajanus cajant0
- Outcome
- direct (15)N fixation ratese1
- Value
- 67 (noninoculated) to 134 kilograms per hectaree1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Cajanus cajan”
e1“the direct (15)N fixation rates ranged from 67 (noninoculated) to 134 kilograms per hectare”
Claim · model-written summary
Grain yields ranged from 540 to 825 kilograms per hectare.
- Taxon
- Cajanus cajanCajanus cajant0
- Outcome
- grain yieldse1
- Value
- 540 to 825 kilograms per hectaree1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Cajanus cajan”
e1“grain yields ranged from 540 to 825 kilograms per hectare”
Claim · model-written summary
Grain yields were not increased with N fertilizer.
- Taxon
- Cajanus cajanCajanus cajant0
- Treatment
- N fertilizere1
- Outcome
- Grain yieldse1
- Direction
- not increasede1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Cajanus cajan”
e1“Grain yields were not increased with N fertilizer”
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