Abstract
Recent studies suggest that alfalfa ( Medicago sativa L.) root carbohydrate concentrations are not correlated closely with shoot regrowth, and that root N reserves may influence shoot regrowth after harvest. The objectives of this greenhouse study were to (i) determine the effects of supplemental N on alfalfa regrowth and N uptake, (ii) quantify N remobilization from roots to regrowing shoots, and (iii) determine if certain root N pools, including vegetative storage proteins (VSPs), were utilized preferentially as N sources during early shoot regrowth. Four cultivars with contrasting fall dormancy reaction were defoliated and supplied with 85 mg N (kg soil) −1 as 15 N‐enriched (NH 4 ) 2 SO 4 or KNO 3 . Samples were taken immediately and once weekly for 28 d. After 28 d, plants were again defoliated and shoots, crowns, and roots of one‐half of the plants sampled immediately. Intact crowns and roots of remaining plants were transplanted into sand, and shoots, crowns, and roots sampled 10 d after transplanting. Taproot N from these samples was partitioned into four specific pools. Nitrate‐N uptake was greater than NH 4 ‐N uptake at 7 and 28 d after N application. Ten days after transplanting, 25% of crown and root total N and 35% of crown and root 15 N was remobilized to regrowing shoots. Fifty‐five percent of total root N was soluble in phosphate buffer. The buffer‐soluble N pool was fractionated into a low molecular weight N pool (≈30% of total root N), a non‐VSP protein N pool (≈20% of total root N), and a VSP‐enriched protein N pool (≈5% of total root N). The low molecular weight N and VSP‐enriched protein N pools in roots were utilized preferentially as N sources for regrowing shoots 10 d after transplanting. Accumulation of these root N pools may be important for rapid early shoot regrowth after defoliation.
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Claims 10
Claim · model-written summary
Nitrate nitrogen uptake exceeded ammonium nitrogen uptake at 7 and 28 days.
- Taxon
- alfalfa
Medicago sativae1 - Treatment
- Nitrate‐Ne0
- Outcome
- uptakee0
- Direction
- greatere0
- Qualifier
- at 7 and 28 d after N applicatione0
- Comparator
- NH 4 ‐Ne0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Nitrate‐N uptake was greater than NH 4 ‐N uptake at 7 and 28 d after N application.”
e1“alfalfa ( Medicago sativa L.)”
Claim · model-written summary
A quarter of crown and root total nitrogen was remobilized to regrowing shoots after transplanting.
- Taxon
- alfalfaMedicago sativae1
- Organ / stage
- regrowing shootse0
- Outcome
- crown and root total Ne0
- Value
- 25%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Ten days after transplanting, 25% of crown and root total N and 35% of crown and root 15 N was remobilized to regrowing shoots.”
e1“alfalfa ( Medicago sativa L.)”
Claim · model-written summary
Thirty-five percent of crown and root labeled nitrogen was remobilized after transplanting.
- Taxon
- alfalfaMedicago sativae1
- Organ / stage
- regrowing shootse0
- Outcome
- crown and root 15 Ne0
- Value
- 35%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Ten days after transplanting, 25% of crown and root total N and 35% of crown and root 15 N was remobilized to regrowing shoots.”
e1“alfalfa ( Medicago sativa L.)”
Claim · model-written summary
Fifty-five percent of root nitrogen was phosphate-buffer soluble.
- Taxon
- alfalfaMedicago sativae1
- Organ / stage
- roote0
- Outcome
- total root N was soluble in phosphate buffere0
- Value
- Fifty‐five percente0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Fifty‐five percent of total root N was soluble in phosphate buffer.”
e1“alfalfa ( Medicago sativa L.)”
Claim · model-written summary
The low molecular weight pool represented about 30% of total root nitrogen.
- Taxon
- alfalfaMedicago sativae1
- Outcome
- low molecular weight N poole0
- Value
- ≈30% of total root Ne0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a low molecular weight N pool (≈30% of total root N)”
e1“alfalfa ( Medicago sativa L.)”
Claim · model-written summary
The non-VSP protein pool represented about 20% of total root nitrogen.
- Taxon
- alfalfaMedicago sativae1
- Outcome
- non‐VSP protein N poole0
- Value
- ≈20% of total root Ne0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a non‐VSP protein N pool (≈20% of total root N)”
e1“alfalfa ( Medicago sativa L.)”
Claim · model-written summary
The VSP enriched pool represented about 5% of total root nitrogen.
- Taxon
- alfalfaMedicago sativae1
- Outcome
- VSP‐enriched protein N poole0
- Value
- ≈5% of total root Ne0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a VSP‐enriched protein N pool (≈5% of total root N)”
e1“alfalfa ( Medicago sativa L.)”
Claim · model-written summary
Low molecular weight root nitrogen was preferentially used for regrowing shoots.
- Taxon
- alfalfaMedicago sativae1
- Organ / stage
- regrowing shootse0
- Outcome
- low molecular weight Ne0
- Qualifier
- 10 d after transplantinge0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The low molecular weight N and VSP‐enriched protein N pools in roots were utilized preferentially as N sources for regrowing shoots 10 d after transplanting.”
e1“alfalfa ( Medicago sativa L.)”
Claim · model-written summary
The VSP enriched root protein pool was preferentially used for regrowing shoots.
- Taxon
- alfalfaMedicago sativae1
- Organ / stage
- regrowing shootse0
- Outcome
- VSP‐enriched protein N poolse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The low molecular weight N and VSP‐enriched protein N pools in roots were utilized preferentially as N sources for regrowing shoots 10 d after transplanting.”
e1“alfalfa ( Medicago sativa L.)”
Claim · model-written summary
Accumulation of these root nitrogen pools may support rapid early shoot regrowth.
- Taxon
- alfalfaMedicago sativae1
- Outcome
- rapid early shoot regrowthe0
- Qualifier
- Accumulation of these root N poolse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Accumulation of these root N pools may be important for rapid early shoot regrowth after defoliation.”
e1“alfalfa ( Medicago sativa L.)”
The same questions in other papers
nitrogen · nutrient: content · Medicago sativa (alfalfa)Positive and negative results
17 papers in the same direction as this paper · 4 in the opposite direction
- no effect
- no effect
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18 papers more in this group
See all 22 papers →Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.