Abstract
Compared with sole nitrate (NO3−) or sole ammonium (NH4+) supply, mixed nitrogen (N) supply may promote growth of maize seedlings. Previous study suggested that mixed N supply not only increased photosynthesis rate, but also enhanced leaf growth by increasing auxin synthesis to build a large sink for C and N utilization. However, whether this process depends on N absorption is unknown. Here, maize seedlings were grown hydroponically with three N forms (NO3− only, 75/25 NO3−/NH4+ and NH4+ only). The study results suggested that maize growth rate and N content of shoots under mixed N supply was little different to that under sole NO3− supply at 0–3 d, but was higher than under sole NO3− supply at 6–9 d. 15N influx rate under mixed N supply was greater than under sole NO3− or NH4+ supply at 6–9 d, although NO3− and NH4+ influx under mixed N supply were reduced compared to sole NO3− and NH4+ supply, respectively. qRT-PCR determination suggested that the increased N absorption under mixed N supply may be related to the higher expression of NO3− transporters in roots, such as ZmNRT1.1A, ZmNRT1.1B, ZmNRT1.1C, ZmNRT1.2 and ZmNRT1.3, or NH4+ absorption transporters, such as ZmAMT1.1A, especially the latter. Furthermore, plants had higher nitrate reductase (NR) glutamine synthase (GS) activity and amino acid content under mixed N supply than when under sole NO3− supply. The experiments with inhibitors of NR reductase and GS synthase further confirmed that N assimilation ability under mixed N supply was necessary to promote maize growth, especially for the reduction of NO3− by NR reductase. This research suggested that the increased processes of NO3− and NH4+ assimilation by improving N-absorption ability of roots under mixed N supply may be the main driving force to increase maize growth.
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Claims 10
Claim · model-written summary
Mixed nitrogen produced little difference in maize growth rate and shoot nitrogen content versus nitrate alone at days 0–3.
- Treatment
- mixed N supplye0
- Outcome
- growth rate and N content of shootse0
- Direction
- little differente0
- Qualifier
- 0–3 de0
- Comparator
- sole NO3− supplye0
Zea maysOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“maize growth rate and N content of shoots under mixed N supply was little different to that under sole NO3− supply at 0–3 d”
Claim · model-written summary
Mixed nitrogen increased maize growth rate and shoot nitrogen content versus nitrate alone at days 6–9.
- Treatment
- mixed N supplye0
- Outcome
- growth rate and N content of shootse0
- Direction
- highere0
- Qualifier
- 6–9 de0
- Comparator
- sole NO3− supplye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“maize growth rate and N content of shoots under mixed N supply was little different to that under sole NO3− supply at 0–3 d, but was higher than under sole NO3− supply at 6–9 d”
Claim · model-written summary
Mixed nitrogen increased 15N influx versus sole nitrate or ammonium at days 6–9.
- Treatment
- mixed N supplye0
- Outcome
- 15N influx ratee0
- Direction
- greatere0
- Qualifier
- 6–9 de0
- Comparator
- sole NO3− or NH4+ supplye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“15N influx rate under mixed N supply was greater than under sole NO3− or NH4+ supply at 6–9 d”
t0“maize”
Claim · model-written summary
Nitrate influx under mixed nitrogen decreased versus sole nitrate.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“NO3− and NH4+ influx under mixed N supply were reduced compared to sole NO3− and NH4+ supply, respectively.”
t0“maize”
Claim · model-written summary
Ammonium influx under mixed nitrogen decreased versus sole ammonium.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“NO3− and NH4+ influx under mixed N supply were reduced compared to sole NO3− and NH4+ supply, respectively.”
t0“maize”
Claim · model-written summary
Mixed nitrogen increased root nitrate transporter expression.
- Treatment
- mixed N supplye1
- Gene
- ZmNRT1.1A, ZmNRT1.1B, ZmNRT1.1C, ZmNRT1.2 and ZmNRT1.3e0
- Outcome
- expression of NO3− transporterse0
- Direction
- highere0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“higher expression of NO3− transporters in roots, such as ZmNRT1.1A, ZmNRT1.1B, ZmNRT1.1C, ZmNRT1.2 and ZmNRT1.3”
e1“absorption under mixed N supply”
t0“maize”
Claim · model-written summary
Mixed nitrogen increased ZmAMT1.1A expression.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“higher expression of NO3− transporters in roots, such as ZmNRT1.1A, ZmNRT1.1B, ZmNRT1.1C, ZmNRT1.2 and ZmNRT1.3, or NH4+ absorption transporters, such as ZmAMT1.1A”
e1“absorption under mixed N supply”
t0“maize”
Claim · model-written summary
Mixed nitrogen increased nitrate reductase and glutamine synthase activity over nitrate alone.
- Treatment
- mixed N supplye0
- Outcome
- nitrate reductase (NR) glutamine synthase (GS) activitye0
- Direction
- highere0
- Comparator
- sole NO3− supplye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“plants had higher nitrate reductase (NR) glutamine synthase (GS) activity and amino acid content under mixed N supply than when under sole NO3− supply.”
t0“maize”
Claim · model-written summary
Mixed nitrogen increased amino acid content over nitrate alone.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“plants had higher nitrate reductase (NR) glutamine synthase (GS) activity and amino acid content under mixed N supply than when under sole NO3− supply.”
t0“maize”
Claim · model-written summary
Inhibitor experiments indicated nitrogen assimilation was necessary for mixed-nitrogen growth promotion.
- Treatment
- inhibitors of NR reductase and GS synthasee0
- Outcome
- maize growthe0
- Qualifier
- N assimilation ability under mixed N supplye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The experiments with inhibitors of NR reductase and GS synthase further confirmed that N assimilation ability under mixed N supply was necessary to promote maize growth, especially for the reduction of NO3− by NR reductase.”
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