Abstract
Two successive lettuce crops were grown in spring 2005 in a completely closed hydroponic system. The ratio of ammonium to total nitrogen ( N r ) in the fresh nutrient solution (FNS) introduced into the closed system to compensate for plant uptake was 0, 0.1, 0.2 and 0.3 on a molar basis. In all N r treatments, the concentrations of total N, K, Ca, Mg, P, and micronutrients in the FNS were identical, but that of SO 4 2– increased as N r increased, to compensate electrochemically for the enhanced NH 4 + and decreased NO 3 – supply. The highest fresh and dry weights per plant were attained with the highest ammonium supply ( N r = 0.3) but, even when no NH 4 + was included in the FNS as an N source, the plants were healthy without apparent nutritional disorders. The ammonium concentration in the drainage solution dropped to nearly zero in all treatments some days after the initiation of recycling, which implies a preferential uptake of NH 4 -N over NO 3 -N. The root zone pH, as indicated by the values measured in the drainage solution, decreased slightly as N r increased, and ranged from 6.5 to 8.0 in all treatments. The leaf K, Ca, Mg, and Fe concentrations were not influenced, whereas those of P, Mn, Zn, and Cu were enhanced by the increasing NH 4 + supply. The increased ammonium supply did not enhance the utilization of N in plant metabolism, although it reduced the nitrate concentration of the internal leaves in the early spring experiment. The leaf micronutrient concentrations were clearly more than critical levels even when NO 3 – was the sole N source for lettuce, whereas the P concentration approached the lowest critical level when N r was 0 or 0.1. The stimulation of lettuce growth as N r was increased to 0.3 may be a consequence of enhanced P uptake resulting from better control of pH in the root zone.
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Claims 13
Claim · model-written summary
The highest ammonium supply yielded the highest fresh and dry weights per lettuce plant.
- Taxon
- lettuce
Lactuca sativat0 - Treatment
- highest ammonium supply ( N r = 0.3)e0
- Outcome
- fresh and dry weights per plante0
- Direction
- higheste0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The highest fresh and dry weights per plant were attained with the highest ammonium supply ( N r = 0.3)”
t0“Lettuce”
Claim · model-written summary
Lettuce remained healthy without apparent nutritional disorders when no ammonium was supplied.
- Taxon
- lettuceLactuca sativat0
- Treatment
- no NH 4 + was included in the FNS as an N sourcee0
- Outcome
- healthy without apparent nutritional disorderse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“even when no NH 4 + was included in the FNS as an N source, the plants were healthy without apparent nutritional disorders”
t0“Lettuce”
Claim · model-written summary
Ammonium in the drainage solution dropped to nearly zero in all treatments after recycling began.
- Taxon
- lettuceLactuca sativat0
- Outcome
- ammonium concentration in the drainage solutione0
- Direction
- dropped to nearly zeroe0
- Qualifier
- some days after the initiation of recyclinge0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The ammonium concentration in the drainage solution dropped to nearly zero in all treatments some days after the initiation of recycling”
t0“Lettuce”
Claim · model-written summary
The drainage result implies preferential ammonium nitrogen uptake over nitrate nitrogen uptake.
- Taxon
- lettuceLactuca sativat0
- Outcome
- preferential uptake of NH 4 -N over NO 3 -Ne0
Not reportedQualifier
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“which implies a preferential uptake of NH 4 -N over NO 3 -N”
t0“Lettuce”
Claim · model-written summary
Root zone pH decreased slightly as the ammonium ratio increased.
- Taxon
- lettuceLactuca sativat0
- Treatment
- N r increasede0
- Outcome
- root zone pHe0
- Direction
- decreased slightlye0
- Value
- 6.5 to 8.0e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The root zone pH, as indicated by the values measured in the drainage solution, decreased slightly as N r increased, and ranged from 6.5 to 8.0 in all treatments”
t0“Lettuce”
Claim · model-written summary
Increasing ammonium supply did not influence leaf potassium, calcium, magnesium or iron concentrations.
- Taxon
- lettuceLactuca sativat0
- Treatment
- increasing NH 4 + supplye1
- Outcome
- leaf K, Ca, Mg, and Fe concentrationse0
- Direction
- not influencede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The leaf K, Ca, Mg, and Fe concentrations were not influenced”
t0“Lettuce”
e1“increasing NH 4 + supply”
Claim · model-written summary
Increasing ammonium supply enhanced leaf phosphorus, manganese and zinc concentrations.
- Taxon
- lettuceLactuca sativat0
- Treatment
- increasing NH 4 + supplye0
- Outcome
- P, Mn, Zne0
- Direction
- enhancede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“those of P, Mn, Zn, and Cu were enhanced by the increasing NH 4 + supply”
t0“Lettuce”
Claim · model-written summary
Increasing ammonium supply enhanced leaf copper concentration.
- Taxon
- lettuceLactuca sativat0
- Treatment
- increasing NH 4 + supplye0
- Outcome
- Cue0
- Direction
- enhancede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“those of P, Mn, Zn, and Cu were enhanced by the increasing NH 4 + supply”
t0“Lettuce”
Claim · model-written summary
Increased ammonium supply did not enhance nitrogen utilization in lettuce metabolism.
- Taxon
- lettuceLactuca sativat0
- Treatment
- increased ammonium supplye0
- Outcome
- utilization of N in plant metabolisme0
- Direction
- did not enhancee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The increased ammonium supply did not enhance the utilization of N in plant metabolism”
t0“Lettuce”
Claim · model-written summary
Increased ammonium supply reduced nitrate concentration in internal leaves in the early spring experiment.
- Taxon
- lettuceLactuca sativat0
- Organ / stage
- internal leavese0
- Treatment
- increased ammonium supplye1
- Outcome
- nitrate concentratione0
- Direction
- reducede0
- Qualifier
- early spring experimente0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“it reduced the nitrate concentration of the internal leaves in the early spring experiment”
t0“Lettuce”
e1“The increased ammonium supply”
Claim · model-written summary
Leaf micronutrient concentrations exceeded critical levels even with nitrate as the sole nitrogen source.
- Taxon
- lettuceLactuca sativae0
- Treatment
- NO 3 – was the sole N sourcee0
- Outcome
- leaf micronutrient concentrationse0
- Direction
- more than critical levelse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The leaf micronutrient concentrations were clearly more than critical levels even when NO 3 – was the sole N source for lettuce”
Claim · model-written summary
Leaf phosphorus approached the lowest critical level at ammonium ratios of zero or 0.1.
- Taxon
- lettuceLactuca sativat0
- Treatment
- N r was 0 or 0.1e0
- Outcome
- P concentratione0
- Direction
- approached the lowest critical levele0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the P concentration approached the lowest critical level when N r was 0 or 0.1”
t0“Lettuce”
Claim · model-written summary
The authors suggest that better root-zone pH control and enhanced phosphorus uptake may explain growth stimulation at an ammonium ratio of 0.3.
- Taxon
- lettuceLactuca sativae0
- Treatment
- N r was increased to 0.3e0
- Outcome
- stimulation of lettuce growthe0
- Qualifier
- may be a consequence of enhanced P uptake resulting from better control of pH in the root zonee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The stimulation of lettuce growth as N r was increased to 0.3 may be a consequence of enhanced P uptake resulting from better control of pH in the root zone”
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