Abstract
Soybeans were grown in a glasshouse in sand-vermiculite medium supplied daily with a mineral nutrient solution essentially free of combined N or containing 5 mM nitrate of known 15N abundance. The natural abundance of 15N in parts of plants and in nitrogen remaining in the medium was determined from 15 days after planting until fruiting. In nodulated plants completely dependent on N2 fixation for growth, the δ15N of plant nitrogen was uniformly negative at 56 days (overall mean: -0.90± 0.17) after adjustment for the effect of seed nitrogen. The δ15N of root nodules increased with time (max. 9.6‰), as that of shoots declined (min. - 1.3 ‰). The δ15N of every mainstem trifoliolate leaf and of the first (unifoliolate) leaf declined from initially positive values (0.5 to 2 ‰) to about - 2‰ with similar time courses, irrespective of the time of initiation. There were no significant losses of N from the plants during growth. There were differences between the δ15N of the total N of root-bleeding xylem sap and of sap extracted by vacuum treatment of stems. These were due to differences between the proportions of ureide-N and amino-N and between the δ15N values of these components. When nodulated plants were supplied daily with 5 mM nitrate (δ15N = 7.68‰) between 21 and 35 days, N2 fixation was reduced to 63% of N assimilated but growth and accumulation of nitrogen were affected little. Following removal of nitrate, there were changes in growth which led to enhanced nodulation and N2 fixation. The δ15N of the total N of trifoliolate leaves which were initiated or expanded before or during the period of nitrate treatment remained positive; those expanded or initiated after the treatment became negative in δ15N, as in the corresponding leaves of untreated nodulated plants. The δ15N of nodules was unaffected by the nitrate treatment. In plants (non-nod. Clark '63) supplied continuously with nitrate, the δ15N of the total N of entire plants rose quickly from values for seeds, but to values significantly higher than in the nitrate. These results are discussed in relation to the effects on the use of 15N natural abundance data for estimating utilisation of atmospheric N2 by nodulated plants.
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Claims 14
Claim · model-written summary
Nodulated plants dependent on fixation had negative nitrogen isotope values at day 56.
- Taxon
- Soybeans
Glycine maxt0 - Outcome
- δ15N of plant nitrogene0
- Value
- -0.90± 0.17e0
- Qualifier
- at 56 dayse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the δ15N of plant nitrogen was uniformly negative at 56 days (overall mean: -0.90± 0.17)”
t0“Soybeans”
Claim · model-written summary
Root nodule δ15N increased over time to 9.6‰.
- Taxon
- SoybeansGlycine maxt0
- Organ / stage
- root nodulese0
- Outcome
- δ15N of root nodulese0
- Direction
- increasede0
- Value
- 9.6‰e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The δ15N of root nodules increased with time (max. 9.6‰)”
t0“Soybeans”
Claim · model-written summary
Shoot δ15N declined over time to −1.3‰.
- Taxon
- SoybeansGlycine maxt0
- Organ / stage
- shootse0
- Outcome
- that of shootse0
- Direction
- declinede0
- Value
- - 1.3 ‰e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“as that of shoots declined (min. - 1.3 ‰)”
t0“Soybeans”
Claim · model-written summary
Leaf δ15N declined from positive values to about −2‰.
- Taxon
- SoybeansGlycine maxt0
- Organ / stage
- mainstem trifoliolate leafe0
- Outcome
- δ15N of every mainstem trifoliolate leaf and of the first (unifoliolate) leafe0
- Direction
- declinede0
- Value
- - 2‰e0
- Qualifier
- 0.5 to 2 ‰e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The δ15N of every mainstem trifoliolate leaf and of the first (unifoliolate) leaf declined from initially positive values (0.5 to 2 ‰) to about - 2‰ with similar time courses”
t0“Soybeans”
Claim · model-written summary
Plants had no significant nitrogen losses during growth.
- Taxon
- SoybeansGlycine maxt0
- Outcome
- losses of Ne0
- Direction
- no significant lossese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“There were no significant losses of N from the plants during growth.”
t0“Soybeans”
Claim · model-written summary
Xylem sap sampling methods yielded different total nitrogen δ15N.
- Taxon
- SoybeansGlycine maxt0
- Outcome
- δ15N of the total N of root-bleeding xylem sape0
- Direction
- differencese0
- Comparator
- sap extracted by vacuum treatment of stemse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“There were differences between the δ15N of the total N of root-bleeding xylem sap and of sap extracted by vacuum treatment of stems.”
t0“Soybeans”
Claim · model-written summary
Differences in sap isotope values arose from ureide and amino nitrogen proportions and isotope values.
- Taxon
- SoybeansGlycine maxt0
- Outcome
- δ15N valuese0
- Qualifier
- differences between the proportions of ureide-N and amino-Ne0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“These were due to differences between the proportions of ureide-N and amino-N and between the δ15N values of these components.”
t0“Soybeans”
Claim · model-written summary
Nitrate supply reduced fixation to 63% of assimilated nitrogen.
- Taxon
- SoybeansGlycine maxt0
- Treatment
- 5 mM nitratee0
- Outcome
- N2 fixatione0
- Direction
- reducede0
- Value
- 63% of N assimilatede0
- Qualifier
- between 21 and 35 dayse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“When nodulated plants were supplied daily with 5 mM nitrate (δ15N = 7.68‰) between 21 and 35 days, N2 fixation was reduced to 63% of N assimilated”
t0“Soybeans”
Claim · model-written summary
Nitrate supply affected growth and nitrogen accumulation little.
- Taxon
- SoybeansGlycine maxt0
- Treatment
- 5 mM nitratee1
- Outcome
- growth and accumulation of nitrogene0
- Direction
- affected littlee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“but growth and accumulation of nitrogen were affected little.”
t0“Soybeans”
e1“When nodulated plants were supplied daily with 5 mM nitrate (δ15N = 7.68‰) between 21 and 35 days, N2 fixation was reduced to 63% of N assimilated”
Claim · model-written summary
Nitrate removal enhanced nodulation and fixation.
- Taxon
- SoybeansGlycine maxt0
- Treatment
- removal of nitratee0
- Outcome
- nodulation and N2 fixatione0
- Direction
- enhancede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Following removal of nitrate, there were changes in growth which led to enhanced nodulation and N2 fixation.”
t0“Soybeans”
Claim · model-written summary
After nitrate treatment, leaves initiated or expanded before or during treatment retained positive δ15N.
- Taxon
- SoybeansGlycine maxt0
- Organ / stage
- trifoliolate leavese0
- Outcome
- δ15N of the total N of trifoliolate leavese0
- Direction
- remained positivee0
- Qualifier
- before or during the period of nitrate treatmente0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The δ15N of the total N of trifoliolate leaves which were initiated or expanded before or during the period of nitrate treatment remained positive”
t0“Soybeans”
Claim · model-written summary
Leaves initiated or expanded after nitrate treatment developed negative δ15N.
- Taxon
- SoybeansGlycine maxt0
- Outcome
- δ15Ne0
- Direction
- became negativee0
- Qualifier
- after the treatmente0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“those expanded or initiated after the treatment became negative in δ15N”
t0“Soybeans”
Claim · model-written summary
Nitrate treatment did not affect nodule δ15N.
- Taxon
- SoybeansGlycine maxt0
- Treatment
- nitrate treatmente0
- Outcome
- δ15N of nodulese0
- Direction
- unaffectede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The δ15N of nodules was unaffected by the nitrate treatment.”
t0“Soybeans”
Claim · model-written summary
Continuously nitrate supplied nonnodulated plants rose above nitrate in δ15N.
- Taxon
- SoybeansGlycine maxt0
- Material
- non-nod. Clark '63e1
- Outcome
- δ15N of the total N of entire plantse0
- Direction
- rosee0
- Comparator
- the nitratee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the δ15N of the total N of entire plants rose quickly from values for seeds, but to values significantly higher than in the nitrate.”
t0“Soybeans”
e1“In plants (non-nod. Clark '63) supplied continuously with nitrate”
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