Abstract
Nodule formation was inhibited by exposing soybean plants to nitrate in plastic growth pouches. Exposure to 15 millimolar nitrate resulted in a 2.5-fold decrease in the number of nodules formed in the region of the primary root above the mark made at the time of inoculation to indicate the position of the root tip. Serial section analysis of Bradyrhizobium infections in this region revealed that infection initiation was inhibited approximately 3-fold by exposure to nitrate. Both initial cortical cell divisions and infection thread formation were inhibited. If exposure to nitrate was delayed for 18 hours after the time of inoculation, inhibition was much reduced. This indicates that most of the nitrate-sensitive events of infection were functionally complete within less than 18 hours. Exposure to nitrate for periods of 4 to 24 hours after inoculation, followed by transfer to no-nitrate conditions for the remainder of the time, did not result in substantial inhibition of nodule number. This indicates that the effects of nitrate on infection initiation can be almost entirely reversible. Split towel pouches were used to physically separate portions of the primary root exposed to nitrate and portions of the root exposed to rhizobia. In experiments where nitrate was applied either below or above the inoculated region of the primary root, the degree of inhibition of nodulation was not correlated with either the external concentration of nitrate in contact with root cells undergoing infection or with the internal concentration of nitrate in the infectible region of the root. These results indicate that nitrate itself may not directly inhibit infection initiation or induce host regulatory responses.
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Claims 9
Claim · model-written summary
Nitrate exposure inhibited soybean nodule formation.
- Taxon
- soybean
Glycine maxe0 - Treatment
- nitratee0
- Outcome
- Nodule formatione0
- Direction
- inhibitede0
Not reportedInteractorComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Nodule formation was inhibited by exposing soybean plants to nitrate in plastic growth pouches”
Claim · model-written summary
15 mM nitrate reduced nodule number 2.5-fold.
- Taxon
- SoybeanGlycine maxt0
- Organ / stage
- primary roote0
- Treatment
- 15 millimolar nitratee0
- Outcome
- number of nodulese0
- Direction
- decreasee0
- Value
- 2.5-folde0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Exposure to 15 millimolar nitrate resulted in a 2.5-fold decrease in the number of nodules formed in the region of the primary root”
t0“Soybean”
Claim · model-written summary
Nitrate inhibited Bradyrhizobium infection initiation about threefold.
- Taxon
- SoybeanGlycine maxt0
- Treatment
- nitratee0
- Interactor
- Bradyrhizobium
Bradyrhizobiume0symbiont - Outcome
- Bradyrhizobium infectionse0
- Direction
- inhibitede0
- Value
- approximately 3-folde0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Bradyrhizobium infections in this region revealed that infection initiation was inhibited approximately 3-fold by exposure to nitrate”
t0“Soybean”
Claim · model-written summary
Nitrate inhibited initial cortical cell divisions and infection thread formation.
- Taxon
- SoybeanGlycine maxt0
- Outcome
- initial cortical cell divisions and infection thread formatione0
- Direction
- inhibitede0
Not reportedTreatmentComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Both initial cortical cell divisions and infection thread formation were inhibited”
t0“Soybean”
Claim · model-written summary
Delaying nitrate exposure 18 hours greatly reduced inhibition.
- Taxon
- SoybeanGlycine maxt0
- Treatment
- exposure to nitrate was delayed for 18 hourse0
- Outcome
- inhibitione0
- Direction
- much reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“If exposure to nitrate was delayed for 18 hours after the time of inoculation, inhibition was much reduced”
t0“Soybean”
Claim · model-written summary
A 4 to 24 hour nitrate pulse did not substantially inhibit nodule number after removal.
- Taxon
- SoybeanGlycine maxt0
- Treatment
- Exposure to nitrate for periods of 4 to 24 hours after inoculatione0
- Outcome
- nodule numbere0
- Direction
- did not result in substantial inhibitione0
- Comparator
- no-nitrate conditionse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Exposure to nitrate for periods of 4 to 24 hours after inoculation, followed by transfer to no-nitrate conditions for the remainder of the time, did not result in substantial inhibition of nodule number”
t0“Soybean”
Claim · model-written summary
Local external nitrate concentration did not correlate with nodulation inhibition.
- Taxon
- SoybeanGlycine maxt0
- Compound
- nitratee0
- Outcome
- degree of inhibition of nodulatione0
- Direction
- not correlatede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the degree of inhibition of nodulation was not correlated with either the external concentration of nitrate in contact with root cells undergoing infection or with the internal concentration of nitrate in the infectible region of the root”
t0“Soybean”
Claim · model-written summary
Internal nitrate concentration did not correlate with nodulation inhibition.
- Taxon
- SoybeanGlycine maxt0
- Organ / stage
- roote0
- Outcome
- degree of inhibition of nodulatione0
- Direction
- not correlatede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the degree of inhibition of nodulation was not correlated with either the external concentration of nitrate in contact with root cells undergoing infection or with the internal concentration of nitrate in the infectible region of the root”
t0“Soybean”
Claim · model-written summary
Authors infer nitrate may not directly inhibit infection initiation or induce host regulation.
- Taxon
- SoybeanGlycine maxt0
- Compound
- nitratee0
- Outcome
- infection initiation or induce host regulatory responsese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“nitrate itself may not directly inhibit infection initiation or induce host regulatory responses”
t0“Soybean”
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