Abstract
The effect of short- and long-term changes in shoot carbon-exchange rate (CER) on soybean (Glycine max [L.] Merr.) root nodule activity was assessed to determine whether increases in photosynthate production produce a direct enhancement of symbiotic N(2) fixation. Shoot CER, root + nodule respiration, and apparent N(2) fixation (acetylene reduction) were measured on intact soybean plants grown at 700 microeinsteins per meter per second, with constant root temperature and a 14/10-hour light/dark cycle. There was no diurnal variation of root + nodule respiration or apparent N(2) fixation in plants assayed weekly from 14 to 43 days after planting. However, if plants remained in darkness following their normal dark period, a significant decline in apparent N(2) fixation was measured within 4 hours, and decreasing CO(2) concentration from 320 to 90 microliters CO(2) per liter produced diurnal changes in root nodule activity. Increasing shoot CER by 87, 84, and 76% in 2-, 3-, and 4-week-old plants, respectively, by raising the CO(2) concentration around the shoot from 320 to 1,000 microliters CO(2) per liter, had no effect on root + nodule respiration or acetylene-reduction rates during the first 10 hours of the increased CER treatment. When the CO(2)-enrichment treatment was extended in 3-week-old plants, the only measured parameter that differed significantly after 3 days was shoot CER. After 5 days of continuous CO(2) enrichment, root + nodule respiration and acetylene reduction increased, but such changes reflected an increase in root nodule mass rather than greater specific root nodule activity. The results show that on a 24-hour basis the process of symbiotic N(2) fixation in soybean plants grown under controlled environmental conditions functioned at maximum capacity and was not limited by shoot CER. Whether N(2)-fixation capacity was limited by photosynthate movement to root nodules or by saturation of metabolic processes in root nodules is not known.
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Claims 8
Claim · model-written summary
No diurnal variation of root plus nodule respiration or apparent N2 fixation occurred in soybean plants assayed weekly from 14 to 43 days after planting.
- Taxon
- Soybean
Glycine maxt0 - Outcome
- diurnal variation of root + nodule respiration or apparent N(2) fixatione1
- Direction
- no diurnal variatione1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Soybean Root Nodule Activity”
e1“There was no diurnal variation of root + nodule respiration or apparent N(2) fixation in plants assayed weekly from 14 to 43 days after planting”
Claim · model-written summary
When soybean plants stayed in darkness after their normal dark period, apparent N2 fixation declined significantly within 4 hours.
- Taxon
- SoybeanGlycine maxt0
- Treatment
- darkness following their normal dark periode1
- Outcome
- apparent N(2) fixatione1
- Direction
- declinee1
- Qualifier
- within 4 hourse1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Soybean Root Nodule Activity”
e1“if plants remained in darkness following their normal dark period, a significant decline in apparent N(2) fixation was measured within 4 hours”
Claim · model-written summary
Decreasing CO2 concentration from 320 to 90 microliters per liter produced diurnal changes in soybean root nodule activity.
- Taxon
- SoybeanGlycine maxt0
- Treatment
- decreasing CO(2) concentration from 320 to 90 microliters CO(2) per litere1
- Outcome
- diurnal changes in root nodule activitye1
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Soybean Root Nodule Activity”
e1“decreasing CO(2) concentration from 320 to 90 microliters CO(2) per liter produced diurnal changes in root nodule activity”
Claim · model-written summary
Raising shoot CER by 87, 84 and 76% in 2-, 3- and 4-week-old plants through CO2 enrichment (320 to 1,000 microliters per liter) had no effect on root plus nodule respiration or acetylene-reduction rates during the first 10 hours.
- Taxon
- SoybeanGlycine maxt0
- Treatment
- raising the CO(2) concentration around the shoot from 320 to 1,000 microliters CO(2) per litere1
- Outcome
- root + nodule respiration or acetylene-reduction ratese1
- Direction
- no effecte1
- Qualifier
- during the first 10 hours of the increased CER treatmente1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Soybean Root Nodule Activity”
e1“Increasing shoot CER by 87, 84, and 76% in 2-, 3-, and 4-week-old plants, respectively, by raising the CO(2) concentration around the shoot from 320 to 1,000 microliters CO(2) per liter, had no effect on root + nodule respiration or acetylene-reduction rates during the first 10 hours of the increased CER treatment”
Claim · model-written summary
When CO2 enrichment was extended in 3-week-old plants, shoot CER was the only measured parameter that differed significantly after 3 days.
- Taxon
- SoybeanGlycine maxt0
- Treatment
- CO(2)-enrichment treatmente1
- Outcome
- shoot CERe1
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Soybean Root Nodule Activity”
e1“When the CO(2)-enrichment treatment was extended in 3-week-old plants, the only measured parameter that differed significantly after 3 days was shoot CER”
Claim · model-written summary
After 5 days of continuous CO2 enrichment, root plus nodule respiration and acetylene reduction increased.
- Taxon
- SoybeanGlycine maxt0
- Treatment
- continuous CO(2) enrichmente1
- Outcome
- root + nodule respiration and acetylene reductione1
- Direction
- increasede1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Soybean Root Nodule Activity”
e1“After 5 days of continuous CO(2) enrichment, root + nodule respiration and acetylene reduction increased”
Claim · model-written summary
The increases in respiration and acetylene reduction after 5 days reflected greater root nodule mass rather than greater specific nodule activity.
- Taxon
- SoybeanGlycine maxt0
- Outcome
- root + nodule respiration and acetylene reductione1
- Qualifier
- reflected an increase in root nodule mass rather than greater specific root nodule activitye1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Soybean Root Nodule Activity”
e1“root + nodule respiration and acetylene reduction increased, but such changes reflected an increase in root nodule mass rather than greater specific root nodule activity”
Claim · model-written summary
On a 24-hour basis, symbiotic N2 fixation in soybean grown under controlled conditions functioned at maximum capacity and was not limited by shoot CER.
- Taxon
- SoybeanGlycine maxt0
- Outcome
- symbiotic N(2) fixatione1
- Qualifier
- functioned at maximum capacity and was not limited by shoot CERe1
- Setting
- controlled environmental conditionse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Soybean Root Nodule Activity”
e1“the process of symbiotic N(2) fixation in soybean plants grown under controlled environmental conditions functioned at maximum capacity and was not limited by shoot CER”
The same questions in other papers
light · symbiosis · Glycine max (soybean)Results differ
7 papers in the same direction as this paper · 7 in the opposite direction
- positive
- negative
- negative
11 papers more in this group
See all 15 papers →co2 · physiology: respiration · Glycine max (soybean)Positive and negative results
2 papers in the same direction as this paper · 1 in the opposite direction
- positive
- no effect
- negative
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.