Abstract
Nitrogen mobilization, nitrogen uptake and growth of cuttings obtained from poplar stock plants fertigated with different nitrogen (N) treatments and sprayed with urea in autumn were studied. Stock plants propagated from poplar cuttings were trained to a single shoot and fertigated with 0, 5, 10, 15 or 20 mmol l(-1) N during the first growing season. In October, a subset of stock plants from each N fertigation treatment was sprayed twice with either 3% urea or water, and overwintered outside. In March, total tree biomass and total N concentration and content of stems were estimated for stock plants in each treatment, and cuttings were taken from the middle of each stock plant and stored in plastic bags at 2 degrees C. In mid-April, cuttings were planted in 7.5-l pots containing N-free medium and grown outdoors with a weekly fertigation with nutrient solution containing 0 or 10 mmol l(-1) 15NH4 15NO3. In mid-July, cuttings were harvested, and new shoot (new stems and leaves), shank (old cutting stem) and roots were analyzed for new biomass growth and total N and 15N content. Growth of stock plants was positively related to N supply in the previous growing season. Foliar urea application in autumn had no effect on subsequent stock plant growth even though urea sprays increased both N concentration and content in stem tissues. Biomass growth of cuttings obtained from stock plants was closely related to their N content when the cuttings were grown in an N-free medium regardless of previous treatments applied to the stock plants. When N was supplied in the growth medium, the strength of the relationship between regrowth and N content of cuttings was significantly reduced. Cuttings from stock plants treated with foliar urea and grown in a N-free medium remobilized between 75 and 82% of their total N for new growth, whereas cuttings from plants receiving no urea spray remobilized only between 60 and 69% of their total N for new growth. Current N fertilization of the cuttings reduced the percentage of N remobilized. We conclude that new growth of poplar cuttings in spring was more dependent on currently applied N than on reserve N, and urea N applied as a spray in autumn was more easily remobilized than N taken up by roots during the previous season.
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Claims 10
Claim · model-written summary
Poplar stock-plant growth was positively related to prior nitrogen supply.
- Treatment
- N supply in the previous growing seasone0
- Outcome
- Growth of stock plantse0
- Direction
- positively relatede0
PopulusOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Growth of stock plants was positively related to N supply in the previous growing season.”
e1“poplar stock plants”
Claim · model-written summary
Autumn foliar urea had no effect on subsequent poplar stock-plant growth.
- Treatment
- Foliar urea application in autumne0
- Outcome
- subsequent stock plant growthe0
- Direction
- no effecte0
- Comparator
- watere2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Foliar urea application in autumn had no effect on subsequent stock plant growth”
e1“poplar stock plants”
e2“either 3% urea or water”
Claim · model-written summary
Autumn urea sprays increased stem nitrogen concentration and content in poplar.
- Organ / stage
- stem tissuese0
- Treatment
- urea sprayse0
- Outcome
- N concentration and contente0
- Direction
- increasede0
- Comparator
- watere2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“urea sprays increased both N concentration and content in stem tissues”
e1“poplar stock plants”
e2“either 3% urea or water”
Claim · model-written summary
In nitrogen-free medium, poplar cutting biomass growth was closely related to cutting nitrogen content regardless of prior stock-plant treatments.
- Organ / stage
- cuttingse0
- Outcome
- Biomass growth of cuttingse0
- Direction
- closely relatede0
- Qualifier
- N contente0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Biomass growth of cuttings obtained from stock plants was closely related to their N content when the cuttings were grown in an N-free medium regardless of previous treatments applied to the stock plants.”
t0“from poplar stock plants”
Claim · model-written summary
Nitrogen supplied in growth medium significantly weakened the relation between poplar cutting regrowth and nitrogen content.
- Treatment
- N was supplied in the growth mediume0
- Outcome
- strength of the relationship between regrowth and N content of cuttingse0
- Direction
- reducede0
- Comparator
- N-free mediume2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“When N was supplied in the growth medium, the strength of the relationship between regrowth and N content of cuttings was significantly reduced.”
t0“from poplar stock plants”
e2“when the cuttings were grown in an N-free medium”
Claim · model-written summary
Urea-treated stock-plant cuttings in nitrogen-free medium remobilized 75–82% of their nitrogen for new growth.
- Organ / stage
- Cuttingse0
- Treatment
- foliar ureae0
- Outcome
- total N for new growthe0
- Value
- between 75 and 82%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Cuttings from stock plants treated with foliar urea and grown in a N-free medium remobilized between 75 and 82% of their total N for new growth”
t0“from poplar stock plants”
Claim · model-written summary
Cuttings without stock-plant urea spray remobilized 60–69% of total nitrogen for new growth.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“cuttings from plants receiving no urea spray remobilized only between 60 and 69% of their total N for new growth”
t0“from poplar stock plants”
Claim · model-written summary
Current nitrogen fertilization reduced the percentage of nitrogen remobilized by poplar cuttings.
- Treatment
- Current N fertilizatione0
- Outcome
- percentage of N remobilizede0
- Direction
- reducede0
- Comparator
- 0e2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Current N fertilization of the cuttings reduced the percentage of N remobilized.”
t0“from poplar stock plants”
e2“0 or 10 mmol l(-1) 15NH4 15NO3”
Claim · model-written summary
The authors concluded spring regrowth of poplar cuttings depended more on current nitrogen than reserve nitrogen.
- Outcome
- new growth of poplar cuttings in springe0
- Direction
- more dependente0
- Qualifier
- currently applied Ne0
- Comparator
- reserve Ne0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“new growth of poplar cuttings in spring was more dependent on currently applied N than on reserve N”
Claim · model-written summary
The authors concluded autumn-sprayed urea nitrogen was more readily remobilized than prior-season root-absorbed nitrogen.
- Outcome
- urea N applied as a spray in autumne0
- Direction
- more easily remobilizede0
- Comparator
- N taken up by roots during the previous seasone0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“urea N applied as a spray in autumn was more easily remobilized than N taken up by roots during the previous season”
t0“from poplar stock plants”
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