Abstract
Seedlings of Italian ryegrass (Lolium multiflorum Lam. cv. RVP) and clonal stolon cuttings of white clover (Trifolium repens L. cv. Blanca) were grown for 19 d in flowing solution culture, with N supplied as either 250 mmol m−3 NO3− or NH3+ .Rates of net uptake, influx and translocation of NO3− and NH4+ were then determined using 15N and 13N labelling techniques: between 3–5 h into the photoperiod following 8 h darkness for white clover (CL), and for ryegrass plants that were either entire (IL) or with shoots excised 90 min prior to 13N influx (IC); and 75 min into the photoperiod following 37–39 h darkness for ryegrass (ID). Rates of net uptake, influx and efflux of NH4+ exceeded those of NO3− in IL and IC ryegrass plants: the opposite occurred in white clover (CL). The decrease in net uptake following defoliation of ryegrass was greater for NH4+ (62%) than NO3− (40%). For NH4+ this was associated with a large decrease in influx from 11·0 to 6.0μmol h−1 g−1 root fr. wt; but for NO3−, influx only decreased from 4·2 to 3·7 μmol h−1 g−1. Prolonged exposure to darkness (ID plants) also lowered net uptake of NO3− and NH4+ by, respectively, 86% and 95% of IL levels. For NH4+ this was characterized by a large decrease in influx and a small decrease in efflux; whilst for NO3− the effect of a large decrease in influx was reinforced by a smaller increase in efflux. The data were used to estimate the translocatory fluxes of NO3− (0·3–2·0μmol h−1 g−1) and NH4+ (0·03–0.4μmol h−1 g−1), assimilation in the roots of NO3−(0·2–2 6μmol h−1 g−1) and NH+4 (0·5–8·9 μmol h−1 g−1), and the concentrations of NO3− (9–15 mol m−3) in the cytoplasmic compartment of the roots. The relevance of variable influx and efflux to models for the regulation of N uptake is discussed.
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Claims 16
Claim · model-written summary
In entire and decapitated ryegrass plants, rates of net uptake, influx and efflux of NH4+ exceeded those of NO3−.
LoliumOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“Rates of net uptake, influx and efflux of NH4+ exceeded those of NO3− in IL and IC ryegrass plants”
Claim · model-written summary
In white clover the opposite occurred: rates of net uptake, influx and efflux of NO3− exceeded those of NH4+.
- Taxon
- white clover
Trifolium repense1 - Outcome
- Rates of net uptake, influx and efflux of NH4+e1
- Direction
- the opposite occurrede1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“Rates of net uptake, influx and efflux of NH4+ exceeded those of NO3− in IL and IC ryegrass plants: the opposite occurred in white clover (CL)”
Claim · model-written summary
Defoliation of ryegrass decreased net uptake of NH4+ by 62%, a greater decrease than for NO3−.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“The decrease in net uptake following defoliation of ryegrass was greater for NH4+ (62%) than NO3− (40%)”
Claim · model-written summary
Defoliation of ryegrass decreased net uptake of NO3− by 40%.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“The decrease in net uptake following defoliation of ryegrass was greater for NH4+ (62%) than NO3− (40%)”
Claim · model-written summary
After defoliation of ryegrass, NH4+ influx decreased from 11.0 to 6.0 umol per h per g root fresh weight.
- Treatment
- defoliatione2
- Compound
- NH4+e1
- Outcome
- influxe1
- Direction
- decreasee1
- Value
- 11·0 to 6.0μmol h−1 g−1 root fr. wte1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“For NH4+ this was associated with a large decrease in influx from 11·0 to 6.0μmol h−1 g−1 root fr. wt”
e2“defoliation of ryegrass”
Claim · model-written summary
After defoliation of ryegrass, NO3− influx only decreased from 4.2 to 3.7 umol per h per g.
- Treatment
- defoliatione2
- Compound
- NO3−e1
- Outcome
- influxe1
- Direction
- decreasede1
- Value
- 4·2 to 3·7 μmol h−1 g−1e1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“for NO3−, influx only decreased from 4·2 to 3·7 μmol h−1 g−1”
e2“defoliation of ryegrass”
Claim · model-written summary
Prolonged darkness lowered net uptake of NO3− by 86% of IL levels in ryegrass.
- Taxon
- Italian Ryegrass
Lolium multiflorumt0 - Treatment
- Prolonged exposure to darknesse1
- Compound
- NO3−e1
- Outcome
- net uptakee1
- Direction
- lowerede1
- Value
- 86%e1
- Comparator
- IL levelse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“Prolonged exposure to darkness (ID plants) also lowered net uptake of NO3− and NH4+ by, respectively, 86% and 95% of IL levels”
t0“Italian Ryegrass”
Claim · model-written summary
Prolonged darkness lowered net uptake of NH4+ by 95% of IL levels in ryegrass.
- Taxon
- Italian RyegrassLolium multiflorumt0
- Treatment
- Prolonged exposure to darknesse1
- Compound
- NH4+e1
- Outcome
- net uptakee1
- Direction
- lowerede1
- Value
- 95%e1
- Comparator
- IL levelse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“Prolonged exposure to darkness (ID plants) also lowered net uptake of NO3− and NH4+ by, respectively, 86% and 95% of IL levels”
t0“Italian Ryegrass”
Claim · model-written summary
For NH4+, prolonged darkness was characterized by a large decrease in influx and a small decrease in efflux.
- Taxon
- Italian RyegrassLolium multiflorumt0
- Treatment
- Prolonged exposure to darknesse2
- Compound
- NH4+e1
- Outcome
- decrease in influx and a small decrease in effluxe1
- Direction
- decreasee1
- Qualifier
- large decrease in influx and a small decrease in effluxe1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“For NH4+ this was characterized by a large decrease in influx and a small decrease in efflux”
e2“Prolonged exposure to darkness”
t0“Italian Ryegrass”
Claim · model-written summary
For NO3−, prolonged darkness caused a large decrease in influx.
- Taxon
- Italian RyegrassLolium multiflorumt0
- Treatment
- Prolonged exposure to darknesse2
- Compound
- NO3−e1
- Outcome
- influxe1
- Direction
- decreasee1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“for NO3− the effect of a large decrease in influx was reinforced by a smaller increase in efflux”
e2“Prolonged exposure to darkness”
t0“Italian Ryegrass”
Claim · model-written summary
For NO3−, prolonged darkness caused a smaller increase in efflux.
- Taxon
- Italian RyegrassLolium multiflorumt0
- Treatment
- Prolonged exposure to darknesse2
- Compound
- NO3−e1
- Outcome
- effluxe1
- Direction
- increasee1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“for NO3− the effect of a large decrease in influx was reinforced by a smaller increase in efflux”
e2“Prolonged exposure to darkness”
t0“Italian Ryegrass”
Claim · model-written summary
Estimated translocatory flux of NO3− was 0.3-2.0 umol per h per g.
Not reportedTaxon
Verbatim
e1“translocatory fluxes of NO3− (0·3–2·0μmol h−1 g−1)”
Claim · model-written summary
Estimated translocatory flux of NH4+ was 0.03-0.4 umol per h per g.
Not reportedTaxon
Verbatim
e1“translocatory fluxes of NO3− (0·3–2·0μmol h−1 g−1) and NH4+ (0·03–0.4μmol h−1 g−1)”
Claim · model-written summary
Estimated root assimilation of NO3− was 0.2-2.6 umol per h per g.
Not reportedTaxon
Verbatim
e1“assimilation in the roots of NO3−(0·2–2 6μmol h−1 g−1) and NH+4 (0·5–8·9 μmol h−1 g−1)”
Claim · model-written summary
Estimated root assimilation of NH4+ was 0.5-8.9 umol per h per g.
Not reportedTaxon
Verbatim
e1“assimilation in the roots of NO3−(0·2–2 6μmol h−1 g−1) and NH+4 (0·5–8·9 μmol h−1 g−1)”
Claim · model-written summary
Estimated NO3− concentration in the cytoplasmic compartment of the roots was 9-15 mol per m3.
- Organ / stage
- cytoplasmic compartment of the rootse1
- Outcome
- concentrations of NO3−e1
- Value
- 9–15 mol m−3e1
Not reportedTaxon
Verbatim
e1“the concentrations of NO3− (9–15 mol m−3) in the cytoplasmic compartment of the roots”