Abstract
Techniques of compartmental (efflux) and kinetic influx analyses with the radiotracer 13NH4+ were used to examine the adaptation to hypoxia (15, 35, and 50% O2 saturation) of root N uptake and metabolism in 3-week-old hydroponically grown rice (Oryza sativa L., cv IR72) seedlings. A time-dependence study of NH4+ influx into rice roots after onset of hypoxia (15% O2) revealed an initial increase in the first 1 to 2.5 h after treatment imposition, followed by a decline to less than 50% of influx in control plants by 4 d. Efflux analyses conducted 0, 1, 3, and 5 d after the treatment confirmed this adaptation pattern of NH4+ uptake. Half-lives for NH4+ exchange with subcellular compartments, cytoplasmic NH4+ concentrations, and efflux (as percentage of influx) were unaffected by hypoxia. However, significant differences were observed in the relative amounts of N allocated to NH4+ assimilation and the vacuole versus translocation to the shoot. Kinetic experiments conducted at 100, 50, 35, and 15% O2 saturation showed no significant change in the Km value for NH4+ uptake with varying O2 supply. However, Vmax was 42% higher than controls at 50% O2 saturation, unchanged at 35%, and 10% lower than controls at 15% O2. The significance of these flux adaptations is discussed.
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Claims 9
Claim · model-written summary
Hypoxia (15% O2) initially increased NH4+ influx into rice roots within the first 1 to 2.5 h after treatment.
- Taxon
- rice
Oryza sativat0 - Organ / stage
- rootse1
- Treatment
- hypoxia (15% O2)e1
- Outcome
- NH4+ influxe1
- Direction
- increasee1
- Qualifier
- in the first 1 to 2.5 h after treatment impositione1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Effects of Hypoxia on 13NH4+Fluxes in Rice Roots1”
e1“A time-dependence study of NH4+ influx into rice roots after onset of hypoxia (15% O2) revealed an initial increase in the first 1 to 2.5 h after treatment imposition, followed by a decline to less than 50% of influx in control plants by 4 d”
Claim · model-written summary
Under hypoxia (15% O2), NH4+ influx into rice roots declined to less than 50% of control influx by 4 d.
- Taxon
- riceOryza sativat0
- Organ / stage
- rootse1
- Treatment
- hypoxia (15% O2)e1
- Outcome
- NH4+ influxe1
- Direction
- declinee1
- Value
- less than 50%e1
- Qualifier
- by 4 de1
- Comparator
- control plantse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Effects of Hypoxia on 13NH4+Fluxes in Rice Roots1”
e1“A time-dependence study of NH4+ influx into rice roots after onset of hypoxia (15% O2) revealed an initial increase in the first 1 to 2.5 h after treatment imposition, followed by a decline to less than 50% of influx in control plants by 4 d”
Claim · model-written summary
Efflux analyses at 0, 1, 3 and 5 d after treatment confirmed the adaptation pattern of NH4+ uptake.
- Taxon
- riceOryza sativat0
- Outcome
- adaptation pattern of NH4+ uptakee2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Effects of Hypoxia on 13NH4+Fluxes in Rice Roots1”
e2“Efflux analyses conducted 0, 1, 3, and 5 d after the treatment confirmed this adaptation pattern of NH4+ uptake”
Claim · model-written summary
Hypoxia left the half-lives for NH4+ exchange with subcellular compartments, cytoplasmic NH4+ concentrations and efflux unaffected.
- Taxon
- riceOryza sativat0
- Treatment
- hypoxiae3
- Outcome
- Half-lives for NH4+ exchange with subcellular compartments, cytoplasmic NH4+ concentrations, and effluxe3
- Direction
- unaffectede3
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Effects of Hypoxia on 13NH4+Fluxes in Rice Roots1”
e3“Half-lives for NH4+ exchange with subcellular compartments, cytoplasmic NH4+ concentrations, and efflux (as percentage of influx) were unaffected by hypoxia”
Claim · model-written summary
Significant differences were observed in the relative N allocation to NH4+ assimilation and the vacuole versus translocation to the shoot in rice roots.
- Taxon
- riceOryza sativat0
- Outcome
- relative amounts of N allocated to NH4+ assimilation and the vacuole versus translocation to the shoote4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Effects of Hypoxia on 13NH4+Fluxes in Rice Roots1”
e4“significant differences were observed in the relative amounts of N allocated to NH4+ assimilation and the vacuole versus translocation to the shoot”
Claim · model-written summary
Kinetic experiments at 100, 50, 35, and 15% O2 saturation showed no significant change in the Km for NH4+ uptake.
- Taxon
- riceOryza sativat0
- Treatment
- 100, 50, 35, and 15% O2 saturatione5
- Outcome
- Km value for NH4+ uptakee5
- Direction
- no significant changee5
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Effects of Hypoxia on 13NH4+Fluxes in Rice Roots1”
e5“Kinetic experiments conducted at 100, 50, 35, and 15% O2 saturation showed no significant change in the Km value for NH4+ uptake with varying O2 supply”
Claim · model-written summary
Vmax was 42% higher than controls at 50% O2 saturation.
- Taxon
- riceOryza sativat0
- Treatment
- 50% O2 saturatione6
- Outcome
- Vmaxe6
- Direction
- highere6
- Value
- 42%e6
- Comparator
- controlse6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Effects of Hypoxia on 13NH4+Fluxes in Rice Roots1”
e6“Vmax was 42% higher than controls at 50% O2 saturation, unchanged at 35%, and 10% lower than controls at 15% O2”
Claim · model-written summary
Vmax was unchanged relative to controls at 35% O2 saturation.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Effects of Hypoxia on 13NH4+Fluxes in Rice Roots1”
e6“Vmax was 42% higher than controls at 50% O2 saturation, unchanged at 35%, and 10% lower than controls at 15% O2”
Claim · model-written summary
Vmax was 10% lower than controls at 15% O2.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Effects of Hypoxia on 13NH4+Fluxes in Rice Roots1”
e6“Vmax was 42% higher than controls at 50% O2 saturation, unchanged at 35%, and 10% lower than controls at 15% O2”
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