Abstract
Soybean (Glycine max cv Hodgson) nitrogenase activity (C(2)H(2) reduction) in the presence or absence of nitrate was studied at various external O(2) tensions. Nitrogenase activity increased with oxygen partial pressure up to 30 kilopascals, which appeared to be the optimum. A parallel increase in ATP/ADP ratios indicated a limitation of respiration rate by low O(2) tensions in the nodule, and the values found for adenine nucleotide ratios suggested that the nitrogenase activity was limited by the rate of ATP regeneration. In the presence of nitrate, the nitrogenase activity was low and less stimulated by increased pO(2), although the nitrite content per gram of nodules decreased from 0.05 to 0.02 micromole when pO(2) increased from 10 to 30 kilopascals. Therefore, the accumulation of nitrite inside the nodule was probably not the major cause of the inhibition. Instead, inhibition by nitrate could be due to competition for reducing power between nitrate reduction and bacteroid or mitochondrial respiration inside the nodule. This is supported by the observation of decrease in ATP/ADP ratios from 1.65, in absence of nitrate, to 0.93 in the presence of this anion at 30 kilopascals O(2). Furthermore, the inhibition was suppressed by the addition, to the plant nutrient solution, of 15 millimolar l-malate, a carbon substrate that is considered to be the major source of reductant for the bacteroids in the symbiosis.
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Claims 10
Claim · model-written summary
Nodule nitrogenase activity rose with oxygen pressure up to an apparent optimum of 30 kilopascals.
- Taxon
- Soybean
Glycine maxt0 - Treatment
- oxygen partial pressuree0
- Outcome
- Nitrogenase activitye0
- Direction
- increasede0
- Value
- 30 kilopascalse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Nitrogenase activity increased with oxygen partial pressure up to 30 kilopascals, which appeared to be the optimum.”
t0“Soybean”
Claim · model-written summary
ATP/ADP ratios increased in parallel with oxygen pressure.
- Taxon
- SoybeanGlycine maxt0
- Treatment
- low O(2) tensionse0
- Outcome
- ATP/ADP ratiose0
- Direction
- increasee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“A parallel increase in ATP/ADP ratios indicated a limitation of respiration rate by low O(2) tensions in the nodule, and the values found for adenine nucleotide ratios suggested that the nitrogenase activity was limited by the rate of ATP regeneration.”
t0“Soybean”
Claim · model-written summary
The authors inferred that low nodule oxygen limited respiration rate.
- Taxon
- SoybeanGlycine maxt0
- Outcome
- limitation of respiration ratee0
- Qualifier
- low O(2) tensions in the nodulee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“A parallel increase in ATP/ADP ratios indicated a limitation of respiration rate by low O(2) tensions in the nodule, and the values found for adenine nucleotide ratios suggested that the nitrogenase activity was limited by the rate of ATP regeneration.”
t0“Soybean”
Claim · model-written summary
The authors inferred that ATP regeneration rate limited nitrogenase activity.
- Taxon
- SoybeanGlycine maxt0
- Outcome
- nitrogenase activity was limitede0
- Qualifier
- rate of ATP regeneratione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“A parallel increase in ATP/ADP ratios indicated a limitation of respiration rate by low O(2) tensions in the nodule, and the values found for adenine nucleotide ratios suggested that the nitrogenase activity was limited by the rate of ATP regeneration.”
t0“Soybean”
Claim · model-written summary
With nitrate, nitrogenase activity was low and less stimulated by increased oxygen pressure.
- Taxon
- SoybeanGlycine maxt0
- Treatment
- presence of nitratee0
- Outcome
- nitrogenase activitye0
- Direction
- less stimulatede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In the presence of nitrate, the nitrogenase activity was low and less stimulated by increased pO(2), although the nitrite content per gram of nodules decreased from 0.05 to 0.02 micromole when pO(2) increased from 10 to 30 kilopascals.”
t0“Soybean”
Claim · model-written summary
Nodule nitrite content fell from 0.05 to 0.02 micromole as oxygen pressure increased from 10 to 30 kilopascals.
- Taxon
- SoybeanGlycine maxt0
- Treatment
- pO(2) increased from 10 to 30 kilopascalse0
- Outcome
- nitrite content per gram of nodulese0
- Direction
- decreasede0
- Value
- 0.05 to 0.02 micromolee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In the presence of nitrate, the nitrogenase activity was low and less stimulated by increased pO(2), although the nitrite content per gram of nodules decreased from 0.05 to 0.02 micromole when pO(2) increased from 10 to 30 kilopascals.”
t0“Soybean”
Claim · model-written summary
The authors judged nodule nitrite accumulation probably not to be the main cause of nitrogenase inhibition.
- Taxon
- SoybeanGlycine maxt0
- Outcome
- inhibitione0
- Qualifier
- accumulation of nitrite inside the nodulee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Therefore, the accumulation of nitrite inside the nodule was probably not the major cause of the inhibition.”
t0“Soybean”
Claim · model-written summary
The authors proposed competition for reducing power as a possible cause of nitrate inhibition.
- Taxon
- SoybeanGlycine maxt0
- Outcome
- inhibition by nitratee0
- Qualifier
- competition for reducing power between nitrate reduction and bacteroid or mitochondrial respiration inside the nodulee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Instead, inhibition by nitrate could be due to competition for reducing power between nitrate reduction and bacteroid or mitochondrial respiration inside the nodule.”
t0“Soybean”
Claim · model-written summary
ATP/ADP ratio decreased from 1.65 without nitrate to 0.93 with nitrate at 30 kilopascals oxygen.
- Taxon
- SoybeanGlycine maxt0
- Treatment
- presence of this anione0
- Outcome
- ATP/ADP ratiose0
- Direction
- decreasee0
- Value
- 1.65e0
- Qualifier
- 0.93e0
- Comparator
- absence of nitratee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“This is supported by the observation of decrease in ATP/ADP ratios from 1.65, in absence of nitrate, to 0.93 in the presence of this anion at 30 kilopascals O(2).”
t0“Soybean”
Claim · model-written summary
Adding 15 millimolar l-malate suppressed nitrate inhibition.
- Taxon
- SoybeanGlycine maxt0
- Treatment
- 15 millimolar l-malatee0
- Outcome
- inhibitione0
- Direction
- suppressede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Furthermore, the inhibition was suppressed by the addition, to the plant nutrient solution, of 15 millimolar l-malate, a carbon substrate that is considered to be the major source of reductant for the bacteroids in the symbiosis.”
t0“Soybean”
The same questions in other papers
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- positive
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See all 27 papers →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.