Abstract
To some extent, the photosynthetic traits of developing leaves of maize are regulated systemically by water and nitrogen. However, it remains unclear whether photosynthesis is systematically regulated via water and nitrogen when maize crops are grown under close (high density) planting conditions. To address this, a field experiment that had a split-split plot arrangement of treatments was designed. Two irrigation levels on local traditional irrigation level (high, I2, 4,050 m 3 ha −1 ) and reduced by 20% (low, I1, 3,240 m 3 ha −1 ) formed the main plots; two levels of nitrogen fertilizer at a local traditional nitrogen level (high, N2, 360 kg ha −1 ) and reduced by 25% (low, N1, 270 kg ha −1 ) formed the split plots; three planting densities of low (D1, 7.5 plants m −2 ), medium (D2, 9.75 plants m −2 ), and high (D3, 12 plants m −2 ) formed the split-split plots. The grain yield, gas exchange, and chlorophyll a fluorescence of the closely planted maize crops were assessed. The results showed that water–nitrogen coupling regulated their net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), quantum yield of non-regulated non-photochemical energy loss [Y(NO)], actual photochemical efficiency of PSII [Y(II)], and quantum yield of regulated non-photochemical energy loss [Y(NPQ)]. When maize plants were grown at low irrigation with traditional nitrogen and at a medium density (i.e., I1N2D2), they had Pn, Gs, and Tr higher than those of grown under traditional treatment conditions (i.e., I2N2D1). Moreover, the increased photosynthesis in the leaves of maize in the I1N2D2 treatment was mainly caused by decreased Y(NO), and increased Y(II) and Y(NPQ). The coupling of 20%-reduced irrigation with the traditional nitrogen application boosted the grain yield of medium density-planted maize, whose Pn, Gs, Tr, Y(II), and Y(NPQ) were enhanced, and its Y(NO) was reduced. Redundancy analysis revealed that both Y(II) and SPAD were the most important physiological factors affecting maize yield performance, followed by Y(NPQ) and NPQ. Using the 20% reduction in irrigation and traditional nitrogen application at a medium density of planting (I1N2D2) could thus be considered as feasible management practices, which could provide technical guidance for further exploring high yields of closely planted maize plants in arid irrigation regions.
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Claims 10
Claim · model-written summary
Water–nitrogen coupling regulated net photosynthetic rate, stomatal conductance and transpiration rate.
- Treatment
- water–nitrogen couplinge0
- Outcome
- net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr)e0
Zea maysOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“water–nitrogen coupling regulated their net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr)”
e1“in the leaves of maize in the I1N2D2 treatment”
Claim · model-written summary
Water–nitrogen coupling regulated three chlorophyll fluorescence energy loss and efficiency measures.
- Treatment
- water–nitrogen couplinge1
- Outcome
- quantum yield of non-regulated non-photochemical energy loss [Y(NO)], actual photochemical efficiency of PSII [Y(II)], and quantum yield of regulated non-photochemical energy loss [Y(NPQ)]e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“quantum yield of non-regulated non-photochemical energy loss [Y(NO)], actual photochemical efficiency of PSII [Y(II)], and quantum yield of regulated non-photochemical energy loss [Y(NPQ)]”
e1“water–nitrogen coupling regulated”
e2“in the leaves of maize in the I1N2D2 treatment”
Claim · model-written summary
Low irrigation, traditional nitrogen and medium density raised Pn, Gs and Tr relative to traditional conditions.
- Treatment
- low irrigation with traditional nitrogen and at a medium density (i.e., I1N2D2)e0
- Outcome
- Pn, Gs, and Tre0
- Direction
- highere0
- Comparator
- traditional treatment conditions (i.e., I2N2D1)e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“When maize plants were grown at low irrigation with traditional nitrogen and at a medium density (i.e., I1N2D2), they had Pn, Gs, and Tr higher than those of grown under traditional treatment conditions (i.e., I2N2D1).”
Claim · model-written summary
Increased maize leaf photosynthesis under I1N2D2 was mainly attributed to lower Y(NO) and higher Y(II) and Y(NPQ).
- Treatment
- I1N2D2 treatmente0
- Outcome
- increased photosynthesise0
- Qualifier
- decreased Y(NO), and increased Y(II) and Y(NPQ)e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the increased photosynthesis in the leaves of maize in the I1N2D2 treatment was mainly caused by decreased Y(NO), and increased Y(II) and Y(NPQ)”
Claim · model-written summary
Reduced irrigation with traditional nitrogen boosted grain yield at medium planting density.
- Treatment
- 20%-reduced irrigation with the traditional nitrogen applicatione0
- Outcome
- grain yielde0
- Direction
- boostede0
- Qualifier
- medium density-plantede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The coupling of 20%-reduced irrigation with the traditional nitrogen application boosted the grain yield of medium density-planted maize”
Claim · model-written summary
The yield boosting treatment enhanced Pn, Gs and Tr.
- Treatment
- 20%-reduced irrigation with the traditional nitrogen applicatione0
- Outcome
- Pn, Gs, Tre0
- Direction
- enhancede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The coupling of 20%-reduced irrigation with the traditional nitrogen application boosted the grain yield of medium density-planted maize, whose Pn, Gs, Tr, Y(II), and Y(NPQ) were enhanced, and its Y(NO) was reduced.”
Claim · model-written summary
The yield boosting treatment enhanced Y(II) and Y(NPQ).
- Treatment
- 20%-reduced irrigation with the traditional nitrogen applicatione0
- Outcome
- Y(II), and Y(NPQ)e0
- Direction
- enhancede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The coupling of 20%-reduced irrigation with the traditional nitrogen application boosted the grain yield of medium density-planted maize, whose Pn, Gs, Tr, Y(II), and Y(NPQ) were enhanced, and its Y(NO) was reduced.”
Claim · model-written summary
The yield boosting treatment reduced Y(NO).
- Treatment
- 20%-reduced irrigation with the traditional nitrogen applicatione0
- Outcome
- Y(NO)e0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The coupling of 20%-reduced irrigation with the traditional nitrogen application boosted the grain yield of medium density-planted maize, whose Pn, Gs, Tr, Y(II), and Y(NPQ) were enhanced, and its Y(NO) was reduced.”
Claim · model-written summary
Y(II) and SPAD were the most important physiological factors associated with maize yield performance, followed by Y(NPQ) and NPQ.
- Outcome
- maize yield performancee0
- Qualifier
- most important physiological factorse0
- Comparator
- Y(NPQ) and NPQe0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“both Y(II) and SPAD were the most important physiological factors affecting maize yield performance, followed by Y(NPQ) and NPQ”
Claim · model-written summary
The authors recommend I1N2D2 as feasible management for high yields of closely planted maize in arid irrigation regions.
- Treatment
- 20% reduction in irrigation and traditional nitrogen application at a medium density of planting (I1N2D2)e0
- Outcome
- feasible management practicese0
- Setting
- arid irrigation regionse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Using the 20% reduction in irrigation and traditional nitrogen application at a medium density of planting (I1N2D2) could thus be considered as feasible management practices, which could provide technical guidance for further exploring high yields of closely planted maize plants in arid irrigation regions.”
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