Abstract
Recent evidence from other workers indicates that NH4+ transport through the symbiosome membrane of soybean (Glycine max (L.) Merr.) nodules may occur via an ion channel; the transport channel was reported to be inhibited by very low concentrations of Ca. Two approaches were used to assess the Ca-sensitivity of N input from nodules; first, by providing up to 12-fold excess Ca in nutrient solutions. Second, strains of Bradyrhizobium japonicum that synthesize or do not synthesize an anionic polysaccharide in the peribacteroid space were compared; the rationale here was that the polysaccharide may bind Ca in quantities sufficient to avoid Ca inhibition of N transport. After 7-9 weeks of plant growth under the nutrient treatments, plant growth, mineral content, and N variables were measured; results from two similar experiments are reported. The concentration of Ca (and other elements) was estimated in situ in infected cells of nodules by using Energy Dispersive X-ray Analysis. The 12-fold increase in Ca supply led to increases in [Ca] in the infected cells of 2- to 3-fold. Increases in [Ca] were correlated with a decline in [K] in nodules containing polysaccharide. Elevation of [Ca] in infected cells depressed N content of shoots by 17–30% depending on the rhizobial strain and experiment. Effects of Ca on acetylene reduction activity was not always statistically significant, but the estimates of nitrogenase activity were consistent with the results for N content of shoots. The overall results support the idea that N transport from bacteroids is sensitive to Ca concentration in the peribacteroid space. There was no significant difference between bacterial strains, indicating that the polysaccharide deposited in the peribacteroid space does not enhance N transport by binding Ca when Ca concentration is high.
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Claims 5
Claim · model-written summary
A 12-fold increase in calcium supply raised calcium concentration in infected cells 2- to 3-fold.
- Taxon
- soybean
Glycine maxt0 - Treatment
- 12-fold increase in Ca supplye0
- Outcome
- [Ca] in the infected cellse0
- Direction
- increasese0
- Value
- 2- to 3-folde0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The 12-fold increase in Ca supply led to increases in [Ca] in the infected cells of 2- to 3-fold”
t0“soybean (Glycine max (L.) Merr.)”
Claim · model-written summary
Calcium concentration increases correlated with a decline in nodule potassium concentration.
- Taxon
- soybeanGlycine maxt0
- Compound
- [Ca]e0
- Outcome
- [K] in nodulese0
- Direction
- declinee0
- Qualifier
- containing polysaccharidee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Increases in [Ca] were correlated with a decline in [K] in nodules containing polysaccharide”
t0“soybean (Glycine max (L.) Merr.)”
Claim · model-written summary
Elevated calcium concentration depressed shoot nitrogen content by 17–30%.
- Taxon
- soybeanGlycine maxt0
- Treatment
- Elevation of [Ca] in infected cellse0
- Outcome
- N content of shootse0
- Direction
- depressede0
- Value
- 17–30%e0
- Qualifier
- depending on the rhizobial strain and experimente0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Elevation of [Ca] in infected cells depressed N content of shoots by 17–30% depending on the rhizobial strain and experiment”
t0“soybean (Glycine max (L.) Merr.)”
Claim · model-written summary
Calcium effects on acetylene reduction activity were not always statistically significant.
- Taxon
- soybeanGlycine maxt0
- Treatment
- Cae0
- Outcome
- acetylene reduction activitye0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Effects of Ca on acetylene reduction activity was not always statistically significant”
t0“soybean (Glycine max (L.) Merr.)”
Claim · model-written summary
The bacterial strains did not differ significantly in nitrogen transport.
- Taxon
- soybeanGlycine maxt0
- Outcome
- difference between bacterial strainse0
- Direction
- no significant differencee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“There was no significant difference between bacterial strains”
t0“soybean (Glycine max (L.) Merr.)”
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