Abstract
We report experiments to quantify the relationships between the relative abundance of ureide-N in root-bleeding sap, vacuum-extracted sap, and hot water extracts of stems and petioles of nodulated soybean (Glycine max [L.] Merrill cv Bragg) and the proportion of plant N derived from nitrogen fixation. Additional experiments examined the effects of plant genotype and strain of rhizobia on these relationships. In each of the five experiments reported, plants of cv Bragg (experiment 1), cv Lincoln (experiments 3, 4, 5), or six cultivars/genotypes (experiment 2) were grown in a sand:vermiculite mixture in large pots in a naturally lit, temperature-controlled glasshouse during summer. Pots were inoculated at sowing with effective Bradyrhizobium japonicum CB1809 (USDA 136) or with one of 21 different strains of rhizobia. The proportions of plant N derived from nitrogen fixation were determined using (15)N dilution. In one experiment with CB1809, plants were supplied throughout growth with either N-free nutrients or with nutrients supplemented with 1, 2, 4, or 8 millimolar (15)N-nitrate and harvested on eight occasions between V6 and R7 for root-bleeding sap, vacuum-extracted sap, stems (including petioles), and whole plant dry matter. Analyses of the saps and stem extracts for ureides (allantoin plus allantoic acid), alpha-amino-N, and nitrate, and of dry matter for N and (15)N, indicated a positive effect of nitrate supply on concentrations of nitrate in saps and extracts and a negative effect on ureides and on the proportion of plant N derived from nitrogen fixation. The relative abundance of ureide-N in root-bleeding sap, vacuum-extracted sap (100 [ureide-N]/[ureide-N+ alpha-amino-N + nitrate-N]) and stem extracts (100 [ureide-N]/[ureide-N + nitrate-N]) and the proportion of plant N, derived from nitrogen fixation between successive samplings were highly correlated (r = 0.97-1.00). For each variable, two standard curves were prepared to account for the shifts in the compositions of N solutes of xylem saps and extracts after flowering which were not related to a change in nitrogen fixation. Relationships between relative ureide-N and the proportion of plant N derived from nitrogen fixation were not affected by plant genotype or by strain of rhizobia. Therefore, assessment of nitrogen fixation by soybean using the ureide technique should now be possible with the standard curves presented, irrespective of genotype or strain of rhizobia occupying the nodules.
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Claims 8
Claim · model-written summary
Nitrate supply increased nitrate concentrations in soybean saps and extracts.
- Taxon
- Soybean
Glycine maxt0 - Treatment
- nitrate supplye0
- Outcome
- concentrations of nitrate in saps and extractse0
- Direction
- positive effecte0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a positive effect of nitrate supply on concentrations of nitrate in saps and extracts”
t0“Nodulated Soybean”
Claim · model-written summary
Nitrate supply decreased ureides in soybean saps and extracts.
- Taxon
- SoybeanGlycine maxt0
- Treatment
- nitrate supplye0
- Outcome
- ureidese0
- Direction
- negative effecte0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a positive effect of nitrate supply on concentrations of nitrate in saps and extracts and a negative effect on ureides and on the proportion of plant N derived from nitrogen fixation”
t0“Nodulated Soybean”
Claim · model-written summary
Nitrate supply decreased the proportion of soybean nitrogen derived from fixation.
- Taxon
- SoybeanGlycine maxt0
- Treatment
- nitrate supplye0
- Outcome
- proportion of plant N derived from nitrogen fixatione0
- Direction
- negative effecte0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a positive effect of nitrate supply on concentrations of nitrate in saps and extracts and a negative effect on ureides and on the proportion of plant N derived from nitrogen fixation”
t0“Nodulated Soybean”
Claim · model-written summary
Relative ureide nitrogen and fixation-derived plant nitrogen were highly correlated.
- Taxon
- SoybeanGlycine maxt0
- Organ / stage
- steme0
- Outcome
- proportion of plant N, derived from nitrogen fixatione0
- Value
- r = 0.97-1.00e0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The relative abundance of ureide-N in root-bleeding sap, vacuum-extracted sap (100 [ureide-N]/[ureide-N+ alpha-amino-N + nitrate-N]) and stem extracts (100 [ureide-N]/[ureide-N + nitrate-N]) and the proportion of plant N, derived from nitrogen fixation between successive samplings were highly correlated (r = 0.97-1.00).”
t0“Nodulated Soybean”
Claim · model-written summary
Two standard curves accounted for postflowering changes in nitrogen solute composition unrelated to fixation.
- Taxon
- SoybeanGlycine maxt0
- Outcome
- shifts in the compositions of N solutese0
- Value
- two standard curvese0
- Qualifier
- after floweringe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“For each variable, two standard curves were prepared to account for the shifts in the compositions of N solutes of xylem saps and extracts after flowering which were not related to a change in nitrogen fixation.”
t0“Nodulated Soybean”
Claim · model-written summary
The ureide-fixation relationship was unaffected by soybean genotype.
- Taxon
- SoybeanGlycine maxt0
- Material
- plant genotypee0
- Outcome
- Relationships between relative ureide-N and the proportion of plant N derived from nitrogen fixatione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Relationships between relative ureide-N and the proportion of plant N derived from nitrogen fixation were not affected by plant genotype or by strain of rhizobia.”
t0“Nodulated Soybean”
Claim · model-written summary
The ureide-fixation relationship was unaffected by rhizobial strain.
- Taxon
- SoybeanGlycine maxt0
- Outcome
- Relationships between relative ureide-N and the proportion of plant N derived from nitrogen fixatione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Relationships between relative ureide-N and the proportion of plant N derived from nitrogen fixation were not affected by plant genotype or by strain of rhizobia.”
t0“Nodulated Soybean”
Claim · model-written summary
The authors conclude that standard curves enable ureide-based fixation assessment across genotypes and rhizobial strains.
- Taxon
- soybeanGlycine maxe0
- Outcome
- assessment of nitrogen fixatione0
- Comparator
- standard curvese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“assessment of nitrogen fixation by soybean using the ureide technique should now be possible with the standard curves presented, irrespective of genotype or strain of rhizobia occupying the nodules.”
t0“Nodulated Soybean”
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