Abstract
Ammonium and nitrate nitrogen are the two main forms of inorganic nitrogen (N) available to crops. However, it is not clear how mixtures of ammonium and nitrate N affect N uptake and partitioning in major rice cultivars in southern China. This study investigated the effects of different ammonium nitrogen and nitrate nitrogen mixture treatments (100:0, 75:25, 50:50, 25:75, and 0:100) on the growth, photosynthetic characteristics, nitrogen uptake, gene expression, and yield of different rice cultivars (Mei Xiang Zhan NO. 2: MXZ2; Nan Jing Xiang Zhan: NJXZ). Rice root biomass, tiller number, and yield were increased by 69.5%, 42.5%, and 46.8%, respectively, in the 75:25 ammonium-nitrate mixed treatment compared to the 100:0 ammonium-nitrate mixed treatment. The nitrogen content in rice roots, stems, leaves, and grains increased by 69.5%, 64.0%, 65.5%, and 17.5%, respectively. In addition, compared with MXZ2, NJXZ had a greater proportion of N allocated to leaves and grains. Analysis of root enzyme activities revealed that the 75:25 ammonium-nitrate mixed nutrient treatment increased rice root glutamine synthetase activity by an average of 35.0% and glutamate synthetase activity by an average of 52.0%. Transcriptome analysis revealed that the 75:25 mixed ammonium-nitrate nutrient treatment upregulated the expression of genes related to the nitrogen metabolism transporter pathway. Weighted correlation network analysis revealed that some differentially expressed genes (HISX and RPAB5) regulated the activities of nitrogen-metabolizing enzymes in rice and some (SAT2, CYSKP, SYIM, CHI1, and XIP1) modulated amino acid synthesis; greater expression of these genes was detected in the 75:25 ammonium-nitrate mixed nutrient treatment. The expression characteristics of the above genes were further confirmed by RT‒qPCR. Interestingly, the expression levels of the above genes were significantly correlated with the glutamate synthase activity, photosynthetic rate, and root volume. It is noteworthy that increasing the expression of the aforementioned genes coupled with nitrogen uptake was observed in the three main rice cultivars. These results suggest that the 75:25 ammonium-nitrate mixture may have increased nitrogen-metabolizing enzyme activities and promoted nitrogen uptake through the upregulated expression of nitrogen metabolism-related genes, thereby increasing tiller number and improving rice yield.
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Claims 18
Claim · model-written summary
The 75:25 mixture increased rice root biomass by 69.5% over 100:0.
- Taxon
- Rice
Oryza sativae0e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Rice root biomass, tiller number, and yield were increased by 69.5%, 42.5%, and 46.8%, respectively, in the 75:25 ammonium-nitrate mixed treatment compared to the 100:0 ammonium-nitrate mixed treatment.”
e1“in the 75:25 ammonium-nitrate mixed treatment compared to the 100:0 ammonium-nitrate mixed treatment.”
Claim · model-written summary
The 75:25 mixture increased tiller number by 42.5%.
- Taxon
- RiceOryza sativae0e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Rice root biomass, tiller number, and yield were increased by 69.5%, 42.5%, and 46.8%, respectively, in the 75:25 ammonium-nitrate mixed treatment compared to the 100:0 ammonium-nitrate mixed treatment.”
e1“in the 75:25 ammonium-nitrate mixed treatment compared to the 100:0 ammonium-nitrate mixed treatment.”
Claim · model-written summary
The 75:25 mixture increased yield by 46.8%.
- Taxon
- RiceOryza sativae0e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Rice root biomass, tiller number, and yield were increased by 69.5%, 42.5%, and 46.8%, respectively, in the 75:25 ammonium-nitrate mixed treatment compared to the 100:0 ammonium-nitrate mixed treatment.”
e1“in the 75:25 ammonium-nitrate mixed treatment compared to the 100:0 ammonium-nitrate mixed treatment.”
Claim · model-written summary
Rice root nitrogen content increased by 69.5%.
- Taxon
- riceOryza sativae0e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The nitrogen content in rice roots, stems, leaves, and grains increased by 69.5%, 64.0%, 65.5%, and 17.5%, respectively.”
e1“in the 75:25 ammonium-nitrate mixed treatment compared to the 100:0 ammonium-nitrate mixed treatment.”
Claim · model-written summary
Rice stem nitrogen content increased by 64.0%.
- Taxon
- riceOryza sativae0e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The nitrogen content in rice roots, stems, leaves, and grains increased by 69.5%, 64.0%, 65.5%, and 17.5%, respectively.”
e1“in the 75:25 ammonium-nitrate mixed treatment compared to the 100:0 ammonium-nitrate mixed treatment.”
Claim · model-written summary
Rice leaf nitrogen content increased by 65.5%.
- Taxon
- riceOryza sativae0e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The nitrogen content in rice roots, stems, leaves, and grains increased by 69.5%, 64.0%, 65.5%, and 17.5%, respectively.”
e1“in the 75:25 ammonium-nitrate mixed treatment compared to the 100:0 ammonium-nitrate mixed treatment.”
Claim · model-written summary
Rice grain nitrogen content increased by 17.5%.
- Taxon
- riceOryza sativae0e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The nitrogen content in rice roots, stems, leaves, and grains increased by 69.5%, 64.0%, 65.5%, and 17.5%, respectively.”
e1“in the 75:25 ammonium-nitrate mixed treatment compared to the 100:0 ammonium-nitrate mixed treatment.”
Claim · model-written summary
NJXZ allocated a greater proportion of nitrogen to leaves and grains than MXZ2.
- Taxon
- RiceOryza sativat0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“compared with MXZ2, NJXZ had a greater proportion of N allocated to leaves and grains.”
e1“in the 75:25 ammonium-nitrate mixed treatment compared to the 100:0 ammonium-nitrate mixed treatment.”
t0“Rice”
Claim · model-written summary
The 75:25 mixture increased root glutamine synthetase activity by an average of 35.0%.
- Taxon
- riceOryza sativae0e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the 75:25 ammonium-nitrate mixed nutrient treatment increased rice root glutamine synthetase activity by an average of 35.0% and glutamate synthetase activity by an average of 52.0%.”
e1“in the 75:25 ammonium-nitrate mixed treatment compared to the 100:0 ammonium-nitrate mixed treatment.”
Claim · model-written summary
The 75:25 mixture increased root glutamate synthetase activity by an average of 52.0%.
- Taxon
- riceOryza sativae0e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the 75:25 ammonium-nitrate mixed nutrient treatment increased rice root glutamine synthetase activity by an average of 35.0% and glutamate synthetase activity by an average of 52.0%.”
e1“in the 75:25 ammonium-nitrate mixed treatment compared to the 100:0 ammonium-nitrate mixed treatment.”
Claim · model-written summary
The 75:25 mixture upregulated genes in the nitrogen metabolism transporter pathway.
- Taxon
- RiceOryza sativat0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the 75:25 mixed ammonium-nitrate nutrient treatment upregulated the expression of genes related to the nitrogen metabolism transporter pathway.”
e1“in the 75:25 ammonium-nitrate mixed treatment compared to the 100:0 ammonium-nitrate mixed treatment.”
t0“Rice”
Claim · model-written summary
HISX and RPAB5 were inferred to regulate nitrogen-metabolizing enzyme activities.
- Taxon
- riceOryza sativae0e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“some differentially expressed genes (HISX and RPAB5) regulated the activities of nitrogen-metabolizing enzymes in rice”
e1“in the 75:25 ammonium-nitrate mixed treatment compared to the 100:0 ammonium-nitrate mixed treatment.”
Claim · model-written summary
SAT2, CYSKP, SYIM, CHI1, and XIP1 were inferred to modulate amino acid synthesis.
- Taxon
- RiceOryza sativat0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“some (SAT2, CYSKP, SYIM, CHI1, and XIP1) modulated amino acid synthesis”
e1“in the 75:25 ammonium-nitrate mixed treatment compared to the 100:0 ammonium-nitrate mixed treatment.”
t0“Rice”
Claim · model-written summary
The named genes had greater expression under the 75:25 mixture.
- Taxon
- RiceOryza sativat0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“greater expression of these genes was detected in the 75:25 ammonium-nitrate mixed nutrient treatment.”
e1“in the 75:25 ammonium-nitrate mixed treatment compared to the 100:0 ammonium-nitrate mixed treatment.”
t0“Rice”
Claim · model-written summary
RT-qPCR confirmed the expression characteristics of the named genes.
- Taxon
- RiceOryza sativat0
Not reportedValue
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The expression characteristics of the above genes were further confirmed by RT‒qPCR.”
e1“in the 75:25 ammonium-nitrate mixed treatment compared to the 100:0 ammonium-nitrate mixed treatment.”
t0“Rice”
Claim · model-written summary
Expression levels of the named genes correlated significantly with glutamate synthase activity, photosynthetic rate, and root volume.
- Taxon
- RiceOryza sativat0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the expression levels of the above genes were significantly correlated with the glutamate synthase activity, photosynthetic rate, and root volume.”
e1“in the 75:25 ammonium-nitrate mixed treatment compared to the 100:0 ammonium-nitrate mixed treatment.”
t0“Rice”
Claim · model-written summary
Increased expression of the named genes accompanied nitrogen uptake in three main rice cultivars.
- Taxon
- riceOryza sativae0e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“increasing the expression of the aforementioned genes coupled with nitrogen uptake was observed in the three main rice cultivars.”
e1“in the 75:25 ammonium-nitrate mixed treatment compared to the 100:0 ammonium-nitrate mixed treatment.”
Claim · model-written summary
The authors infer that the 75:25 mixture promotes nitrogen uptake through upregulated nitrogen-metabolism genes and increased enzyme activity, contributing to more tillers and yield.
- Taxon
- riceOryza sativae0e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the 75:25 ammonium-nitrate mixture may have increased nitrogen-metabolizing enzyme activities and promoted nitrogen uptake through the upregulated expression of nitrogen metabolism-related genes, thereby increasing tiller number and improving rice yield.”
e1“in the 75:25 ammonium-nitrate mixed treatment compared to the 100:0 ammonium-nitrate mixed treatment.”
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