Abstract
Abstract The cowpea, ( Vigna unguiculata (L.) Walp.), is considered a drought‐tolerant legume. The N fixation process, however, is sensitive to water stress. This study was conducted to describe the development of nodulation and N fixation of field‐grown Californian cowpeas as influenced by stage of growth and drought. California No. 5 blackeyes were evaluated for nodulation and N fixation (as measured by acetylene reduction assay) utilizing four strains of Rhizobium sp. applied as seed inoculum. Two water regimes were utilized in this study: 1) the well‐watered regime was irrigated when the soil matric potential reached ‐0.6 bars at a depth of 20 cm, 2) the droughted regime received sufficient irrigation to allow good seed emergence, followed by a 42‐day period free of rain or irrigation. Maximum nodulation of 175 mg/plant was observed at flowering in the well‐watered plots versus 15 mg/plant in the droughted plants. Following this development stage, there was no significant difference in nodulation between water regimes. Maximum total nitrogenase activity was 22.5 and 18.8 µmoles of ethylene/plant/hour, respectively at flowering and pod‐fill in the well‐watered plants. The dry regime by contrast achieved a maximum nitrogenase activity of 5.3 and 4.5 µmoles ethylene/plant/hour at pod‐fill and pod yellowing stages of maturity, respectively. Consequently, there was a significant reduction in total nitrogenase activity (mmoles of ethylene/plant/growing season) averaged over four Rhizobium strains from 14.5 in the well‐watered to 3.7 in the droughted regime. This decrease in N fixation capacity did not decrease seed yields of droughted plants below those of well‐watered plants.
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Claims 6
Claim · model-written summary
Nodulation was lower in droughted cowpea plants (15 mg/plant at flowering) than in well-watered plots (175 mg/plant at flowering).
- Taxon
- cowpea
Vigna unguiculatae0 - Treatment
- droughted plantse1
- Outcome
- nodulatione1
- Direction
- lowerinferrede1
- Value
- 15 mg/plante1
- Qualifier
- at floweringe1
- Comparator
- well‐watered plotse1
- Setting
- fieldt0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The cowpea, ( Vigna unguiculata (L.) Walp.), is considered a drought‐tolerant legume”
e1“Maximum nodulation of 175 mg/plant was observed at flowering in the well‐watered plots versus 15 mg/plant in the droughted plants”
t0“Field‐Grown California Cowpeas”
Claim · model-written summary
Nodulation did not differ significantly between water regimes after the flowering stage.
- Taxon
- cowpeaVigna unguiculatae0
- Treatment
- water regimese2
- Outcome
- nodulatione2
- Direction
- no_changeinferrede2
- Qualifier
- Following this development stagee2
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The cowpea, ( Vigna unguiculata (L.) Walp.), is considered a drought‐tolerant legume”
e2“Following this development stage, there was no significant difference in nodulation between water regimes”
Claim · model-written summary
Maximum total nitrogenase activity of well-watered cowpea plants was 22.5 and 18.8 µmoles of ethylene per plant per hour at flowering and pod-fill.
- Taxon
- cowpeaVigna unguiculatae0
- Treatment
- well‐watered plantse3
- Outcome
- total nitrogenase activitye3
- Value
- 22.5 and 18.8 µmoles of ethylene/plant/houre3
- Qualifier
- at flowering and pod‐fille3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The cowpea, ( Vigna unguiculata (L.) Walp.), is considered a drought‐tolerant legume”
e3“Maximum total nitrogenase activity was 22.5 and 18.8 µmoles of ethylene/plant/hour, respectively at flowering and pod‐fill in the well‐watered plants”
Claim · model-written summary
Under the dry regime, maximum nitrogenase activity of cowpea was 5.3 and 4.5 µmoles of ethylene per plant per hour at pod-fill and pod yellowing.
- Taxon
- cowpeaVigna unguiculatae0
- Treatment
- dry regimee4
- Outcome
- nitrogenase activitye4
- Value
- 5.3 and 4.5 µmoles ethylene/plant/houre4
- Qualifier
- at pod‐fill and pod yellowing stages of maturitye4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The cowpea, ( Vigna unguiculata (L.) Walp.), is considered a drought‐tolerant legume”
e4“The dry regime by contrast achieved a maximum nitrogenase activity of 5.3 and 4.5 µmoles ethylene/plant/hour at pod‐fill and pod yellowing stages of maturity, respectively”
Claim · model-written summary
Total nitrogenase activity of cowpea averaged over four Rhizobium strains was significantly reduced under drought, from 14.5 to 3.7 mmoles of ethylene per plant per growing season.
- Taxon
- cowpeaVigna unguiculatae0
- Treatment
- droughted regimee5
- Outcome
- total nitrogenase activitye5
- Direction
- reductione5
- Value
- 3.7e5
- Qualifier
- mmoles of ethylene/plant/growing seasone5
- Comparator
- well‐waterede5
RhizobiumOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The cowpea, ( Vigna unguiculata (L.) Walp.), is considered a drought‐tolerant legume”
e5“Consequently, there was a significant reduction in total nitrogenase activity (mmoles of ethylene/plant/growing season) averaged over four Rhizobium strains from 14.5 in the well‐watered to 3.7 in the droughted regime”
Claim · model-written summary
Seed yields of droughted cowpea plants did not decrease below those of well-watered plants despite lower nitrogen fixation capacity.
- Taxon
- cowpeaVigna unguiculatae0
- Treatment
- droughted plantse6
- Outcome
- seed yieldse6
- Direction
- did not decreasee6
- Comparator
- well‐watered plantse6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The cowpea, ( Vigna unguiculata (L.) Walp.), is considered a drought‐tolerant legume”
e6“This decrease in N fixation capacity did not decrease seed yields of droughted plants below those of well‐watered plants”
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