Abstract
Exposure of nodulated leguminous plants to prolonged periods of continuous darkness has been used as a convenient tool to investigate host plant control on nitrogen fixing systems in legume root nodules. Foliar dark treatment of plants results in a rapid decline in N2-fixation in terms of acetylene reduction activity (ARA) and predisposes the nodules to metabolic and structural senescence. After 2 d of darkness, a significant decrease is seen in nitrogenase (N2-ase) proteins of common bean nodules. The effect of dark treatments on nodule respiration varies with plant species. A variable decrease in nodule carbohydrates is observed in different plant species under dark treatments, but no direct correlation between N2-ase activity and gross levels of carbohydrates present in the nodules has been detected. Usually nodule leghemoglobin (Lb) shows a decrease of variable intensity depending on plant species. The mRNA of Lb, sucrose synthase and glutamine synthetase shows a significant decline within 24 h of complete darkness. Dark-induced acceleration of proteolytic activity and decreased plant growth are reflected in decreased nodule proteins and accumulation of free amino acids following a drop in ARA. Antioxidants such as ascorbic acid and glutathione, along with the enzymes of their oxidation-reduction cycle, show a considerable decrease in their content and activity in nodules from dark-treated plants. Among H2O2 scavengers, nodule catalase activity decreases in most of the plants studied, but peroxidase activity shows an increase. Dark-induced adverse effects on N2-fixation are completely or partially reversible on shifting the plants back to a normal light/dark regime. Significant changes in nodule ultrastructure are induced by dark treatment. Attempts have been made to explain the mechanisms underlying dark-induced changes in nodule functioning.
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Claims 17
Claim · model-written summary
Foliar dark treatment reduced N2-fixation (acetylene reduction activity) in legume nodules.
- Taxon
- legumet0
- Treatment
- Foliar dark treatmente1
- Outcome
- N2-fixation in terms of acetylene reduction activity (ARA)e1
- Direction
- declinee1
Not reportedComparator
Verbatim
t0“legume”
e1“Foliar dark treatment of plants results in a rapid decline in N2-fixation in terms of acetylene reduction activity (ARA) and predisposes the nodules to metabolic and structural senescence”
Claim · model-written summary
Foliar dark treatment predisposed nodules to metabolic and structural senescence.
- Taxon
- legumet0
- Organ / stage
- nodulese1
- Treatment
- Foliar dark treatmente1
- Outcome
- metabolic and structural senescencee1
Not reportedComparatorDirection
Verbatim
t0“legume”
e1“Foliar dark treatment of plants results in a rapid decline in N2-fixation in terms of acetylene reduction activity (ARA) and predisposes the nodules to metabolic and structural senescence”
Claim · model-written summary
After 2 days of darkness, nitrogenase (N2-ase) protein decreased significantly in common bean nodules.
- Taxon
- common bean
Phaseolus vulgarise2 - Organ / stage
- nodulese2
- Treatment
- 2 d of darknesse2
- Gene
- nitrogenase (N2-ase)e2
- Outcome
- nitrogenase (N2-ase) proteinse2
- Direction
- decreasee2
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e2“After 2 d of darkness, a significant decrease is seen in nitrogenase (N2-ase) proteins of common bean nodules”
Claim · model-written summary
The effect of dark treatment on nodule respiration varies with plant species.
- Taxon
- legumet0
- Treatment
- dark treatmentse3
- Outcome
- nodule respiratione3
- Qualifier
- varies with plant speciese3
Not reportedComparatorDirection
Verbatim
t0“legume”
e3“The effect of dark treatments on nodule respiration varies with plant species”
Claim · model-written summary
Dark treatment decreased nodule carbohydrates in different plant species, with variable magnitude.
- Taxon
- legumet0
- Treatment
- dark treatmentse4
- Outcome
- nodule carbohydratese4
- Direction
- decreasee4
- Qualifier
- variablee4
Not reportedComparator
Verbatim
t0“legume”
e4“A variable decrease in nodule carbohydrates is observed in different plant species under dark treatments”
Claim · model-written summary
No direct correlation was detected between N2-ase activity and gross nodule carbohydrate levels.
Verbatim
t0“legume”
e5“no direct correlation between N2-ase activity and gross levels of carbohydrates present in the nodules has been detected”
Claim · model-written summary
Nodule leghemoglobin shows a decrease of variable intensity depending on plant species.
Verbatim
t0“legume”
e6“Usually nodule leghemoglobin (Lb) shows a decrease of variable intensity depending on plant species”
Claim · model-written summary
The mRNA of Lb, sucrose synthase and glutamine synthetase declined significantly within 24 h of complete darkness.
- Taxon
- legumet0
- Treatment
- complete darknesse7
- Gene
- Lb, sucrose synthase and glutamine synthetasee7
- Outcome
- mRNA of Lb, sucrose synthase and glutamine synthetasee7
- Direction
- declinee7
- Qualifier
- within 24 he7
Not reportedComparator
Verbatim
t0“legume”
e7“The mRNA of Lb, sucrose synthase and glutamine synthetase shows a significant decline within 24 h of complete darkness”
Claim · model-written summary
Dark induced an acceleration of proteolytic activity in nodules.
Not reportedComparator
Verbatim
t0“legume”
e0“Dark-induced acceleration of proteolytic activity and decreased plant growth are reflected in decreased nodule proteins and accumulation of free amino acids following a drop in ARA”
Claim · model-written summary
Dark decreased plant growth.
Not reportedComparator
Verbatim
t0“legume”
e0“Dark-induced acceleration of proteolytic activity and decreased plant growth are reflected in decreased nodule proteins and accumulation of free amino acids following a drop in ARA”
Claim · model-written summary
Dark decreased nodule proteins.
- Taxon
- legumet0
- Organ / stage
- nodulee0
- Treatment
- Dark-inducede0
- Outcome
- nodule proteinse0
- Direction
- decreasede0
Not reportedComparator
Verbatim
t0“legume”
e0“Dark-induced acceleration of proteolytic activity and decreased plant growth are reflected in decreased nodule proteins and accumulation of free amino acids following a drop in ARA”
Claim · model-written summary
Dark led to accumulation of free amino acids in nodules following a drop in ARA.
- Taxon
- legumet0
- Treatment
- Dark-inducede0
- Compound
- free amino acidse0
- Outcome
- accumulation of free amino acidse0
- Direction
- increaseinferrede0
Not reportedComparator
Verbatim
t0“legume”
e0“Dark-induced acceleration of proteolytic activity and decreased plant growth are reflected in decreased nodule proteins and accumulation of free amino acids following a drop in ARA”
Claim · model-written summary
Dark treatment decreased the content and activity of ascorbic acid, glutathione and their redox-cycle enzymes in nodules.
- Taxon
- legumet0
- Organ / stage
- nodulese0
- Treatment
- dark-treatede0
- Compound
- ascorbic acid and glutathionee0
- Outcome
- content and activitye0
- Direction
- decreasee0
Not reportedComparator
Verbatim
t0“legume”
e0“Antioxidants such as ascorbic acid and glutathione, along with the enzymes of their oxidation-reduction cycle, show a considerable decrease in their content and activity in nodules from dark-treated plants”
Claim · model-written summary
Nodule catalase activity decreased in most of the legume plants studied.
Verbatim
t0“legume”
e0“Among H2O2 scavengers, nodule catalase activity decreases in most of the plants studied, but peroxidase activity shows an increase”
Claim · model-written summary
Nodule peroxidase activity increased in the legume plants studied.
Verbatim
t0“legume”
e0“Among H2O2 scavengers, nodule catalase activity decreases in most of the plants studied, but peroxidase activity shows an increase”
Claim · model-written summary
Dark-induced adverse effects on N2-fixation were completely or partially reversible when plants returned to a normal light/dark regime.
- Taxon
- legumet0
- Treatment
- shifting the plants back to a normal light/dark regimee0
- Outcome
- N2-fixatione0
- Direction
- reversiblee0
Not reportedComparator
Verbatim
t0“legume”
e0“Dark-induced adverse effects on N2-fixation are completely or partially reversible on shifting the plants back to a normal light/dark regime”
Claim · model-written summary
Dark treatment induced significant changes in nodule ultrastructure.
Not reportedComparatorDirection
Verbatim
t0“legume”
e0“Significant changes in nodule ultrastructure are induced by dark treatment”
The same questions in other papers
light · symbiosis · Phaseolus vulgaris (common bean)Positive and negative results
1 paper in the same direction as this paper · 1 in the opposite direction
- negative
- positive
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.