Abstract
SummaryFoliar-applied urea and ABA, respectively, were evaluated as management tools for apple nursery plants to 1) increase reserve N for plants in low N and 2) enhance growth cessation, leaf senescence and abscission, and cold acclimation for those with high N. Container-grown apple plants (Malm domestica Borkh. ‘Gala’), grafted on M.26 rootstocks, were fertigated weekly with 150 mg l–1 N, from mid-May until 21 August, 18 September and 9 October, to represent relatively early-, mid- and late-N cut-off treatments, respectively. In early October, 3% urea was sprayed twice, at six-day intervals, on some of the early-N plants. In addition, 1000 mg –1 ABA was sprayed twice (at five-day intervals) on some of the mid- or late-N plants in early or mid-October, respectively. Leaf-N concentrations increased linearly with longer periods of N fertigation (2.5, 2.9, and 3.2% in the early-, mid-, and late-N plants, respectively). Growth cessation, leaf senescence and abscission, and stem cold acclimation were delayed when the N cut-off time was postponed. Foliar urea applications to the early-N plants effectively increase reserve N (expressed as total N or soluble protein concentrations) in dormant stem bark, wood, and roots. However, this treatment decreased the concentrations of total non-structural carbohydrates (soluble sugars and starch) in all dormant tissue types. Stem cold hardiness also was reduced by about 2 and 3 K in late fall and mid-winter, respectively. Foliar ABA applications to plants grown under mid- or late-N conditions were effective in enhancing leaf senescence and abscission. This led to improved efficiency of N withdrawal from the leaves into woody tissues, especially under late N cut-off conditions. ABA had no effect on growth cessation and cold acclimation. The increases in reserve N levels, as promoted by urea or ABA, resulted in improved regrowth the following spring.
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Claims 10
Claim · model-written summary
Longer nitrogen fertigation increased leaf nitrogen from 2.5% to 3.2%.
Verbatim
e0“Leaf-N concentrations increased linearly with longer periods of N fertigation (2.5, 2.9, and 3.2% in the early-, mid-, and late-N plants, respectively)”
t0“apple nursery plants”
Claim · model-written summary
Postponing nitrogen cut-off delayed growth cessation, leaf senescence and abscission, and cold acclimation.
- Taxon
- apple nursery plantst0
- Treatment
- N cut-off time was postponede0
- Outcome
- Growth cessation, leaf senescence and abscission, and stem cold acclimatione0
- Direction
- delayede0
Not reportedComparator
Verbatim
e0“Growth cessation, leaf senescence and abscission, and stem cold acclimation were delayed when the N cut-off time was postponed”
t0“apple nursery plants”
Claim · model-written summary
Foliar urea increased reserve nitrogen in dormant stem bark, wood and roots.
- Taxon
- apple nursery plantst0
- Organ / stage
- dormant stem bark, wood, and rootse0
- Treatment
- Foliar urea applicationse0
- Outcome
- reserve N (expressed as total N or soluble protein concentrations)e0
- Direction
- increasee0
Not reportedComparator
Verbatim
e0“Foliar urea applications to the early-N plants effectively increase reserve N (expressed as total N or soluble protein concentrations) in dormant stem bark, wood, and roots”
t0“apple nursery plants”
Claim · model-written summary
Foliar urea decreased nonstructural carbohydrates in dormant tissues.
- Taxon
- apple nursery plantst0
- Organ / stage
- dormant tissue typese0
- Treatment
- this treatmente0
- Outcome
- concentrations of total non-structural carbohydrates (soluble sugars and starch)e0
- Direction
- decreasede0
Not reportedComparator
Verbatim
e0“this treatment decreased the concentrations of total non-structural carbohydrates (soluble sugars and starch) in all dormant tissue types”
t0“apple nursery plants”
Claim · model-written summary
Foliar urea reduced stem cold hardiness by about 2 K in late fall.
- Taxon
- apple nursery plantst0
- Treatment
- Foliar applications of ureat0
- Outcome
- Stem cold hardinesse0
- Direction
- reducede0
- Value
- about 2e0
- Qualifier
- late falle0
Not reportedComparator
Verbatim
e0“Stem cold hardiness also was reduced by about 2 and 3 K in late fall and mid-winter, respectively”
t0“Foliar applications of urea or ABA affect growth cessation, leaf senescence and abscission, cold acclimation and levels of reserve nitrogen and carbohydrates in nitrogen-treated apple nursery plants”
Claim · model-written summary
Foliar urea reduced stem cold hardiness by about 3 K in midwinter.
- Taxon
- apple nursery plantst0
- Treatment
- Foliar applications of ureat0
- Outcome
- Stem cold hardinesse0
- Direction
- reducede0
- Value
- 3 Ke0
- Qualifier
- mid-wintere0
Not reportedComparator
Verbatim
e0“Stem cold hardiness also was reduced by about 2 and 3 K in late fall and mid-winter, respectively”
t0“Foliar applications of urea or ABA affect growth cessation, leaf senescence and abscission, cold acclimation and levels of reserve nitrogen and carbohydrates in nitrogen-treated apple nursery plants”
Claim · model-written summary
Foliar ABA enhanced leaf senescence and abscission.
- Taxon
- apple nursery plantst0
- Treatment
- Foliar ABA applicationse0
- Outcome
- leaf senescence and abscissione0
- Direction
- enhancinge0
Not reportedComparator
Verbatim
e0“Foliar ABA applications to plants grown under mid- or late-N conditions were effective in enhancing leaf senescence and abscission”
t0“apple nursery plants”
Claim · model-written summary
ABA improved nitrogen withdrawal from leaves into woody tissues.
- Taxon
- apple nursery plantst0
- Treatment
- ABAt0
- Outcome
- efficiency of N withdrawal from the leaves into woody tissuese0
- Direction
- improvede0
- Qualifier
- late N cut-off conditionse0
Not reportedComparator
Verbatim
e0“This led to improved efficiency of N withdrawal from the leaves into woody tissues, especially under late N cut-off conditions”
t0“ABA affect growth cessation, leaf senescence and abscission, cold acclimation and levels of reserve nitrogen and carbohydrates in nitrogen-treated apple nursery plants”
Claim · model-written summary
ABA had no effect on growth cessation and cold acclimation.
- Taxon
- apple nursery plantst0
- Treatment
- ABAe0
- Outcome
- growth cessation and cold acclimatione0
- Direction
- no effecte0
Not reportedComparator
Verbatim
e0“ABA had no effect on growth cessation and cold acclimation”
t0“apple nursery plants”
Claim · model-written summary
Higher reserve nitrogen promoted by urea or ABA improved regrowth the next spring.
Verbatim
e0“The increases in reserve N levels, as promoted by urea or ABA, resulted in improved regrowth the following spring”
t0“apple nursery plants”
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