Abstract
The effects of the application of different nitrogen (N) forms via drip-irrigation on the physiological photosynthetic characteristics of rice and their contributions to yield remain incompletely understood. To address this knowledge gap, a field drip-irrigation experiment was conducted from 2020 to 2022 using a high-NUE cultivar (T-43) and a low-NUE cultivar (LX-3). Using a no-nitrogen treatment (CK) as the control, the effects of three nitrogen fertilizer treatments—urea (Urea), ammonium (NH4+), and nitrate (NO3−)—were compared. The main results are as follows. (1) The application of nitrogen significantly increased the biomass (26.74%–30.71%) and yield (40.35%–84.91%). Compared with Urea and NO3−, NH4+ increased the chlorophyll content (Chl) and N metabolic enzyme activity, decreased the abscisic acid (ABA) content, and improved stomatal conductance (Gs). (2) T-43 presented relatively high levels of indole-3-acetic acid (IAA), Chl a + b, and Gs, and a relatively high photosynthetic rate (Pn), whereas LX-3 presented increased ABA levels and reduced Chl a + b, and Gs. (3) Partial least squares path model revealed that under NH4+, IAA was positively correlated with Chl b, Gs, and Fv/Fm, whereas ABA was negatively correlated with Y(II), and Chl a + b. Conversely, the Chl contents decreased, and the ABA and Chl a/b increased in the Urea and NO3− treatments, thereby increasing the contribution of NH4+ (GoF = 0.714) to yield when compared to the yields in the Urea (0.614) and NO3− (0.594). In summary, NH4+ synergistically enhances Chl content, photochemical efficiency, antioxidant capacity, and regulates hormone balance while increasing source–sink dry matter accumulation and distribution, thereby achieving efficient production of drip-irrigated rice in arid areas.
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Claims 15
Claim · model-written summary
Nitrogen application increased rice biomass by 26.74%–30.71%.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The application of nitrogen significantly increased the biomass (26.74%–30.71%) and yield (40.35%–84.91%).”
t0“rice”
Claim · model-written summary
Nitrogen application increased rice yield by 40.35%–84.91%.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The application of nitrogen significantly increased the biomass (26.74%–30.71%) and yield (40.35%–84.91%).”
t0“rice”
Claim · model-written summary
Ammonium increased chlorophyll content and nitrogen metabolic enzyme activity relative to urea and nitrate.
- Taxon
- rice
Oryza sativat0 - Treatment
- NH4+e0
- Outcome
- chlorophyll content (Chl) and N metabolic enzyme activitye0
- Direction
- increasede0
- Comparator
- Urea and NO3−e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Compared with Urea and NO3−, NH4+ increased the chlorophyll content (Chl) and N metabolic enzyme activity”
t0“rice”
Claim · model-written summary
Ammonium decreased ABA content relative to urea and nitrate.
- Taxon
- riceOryza sativat0
- Treatment
- NH4+e0
- Outcome
- abscisic acid (ABA) contente0
- Direction
- decreasede0
- Comparator
- Urea and NO3−e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Compared with Urea and NO3−, NH4+ increased the chlorophyll content (Chl) and N metabolic enzyme activity, decreased the abscisic acid (ABA) content”
t0“rice”
Claim · model-written summary
Ammonium improved stomatal conductance relative to urea and nitrate.
- Taxon
- riceOryza sativat0
- Treatment
- NH4+e0
- Outcome
- stomatal conductance (Gs)e0
- Direction
- improvede0
- Comparator
- Urea and NO3−e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Compared with Urea and NO3−, NH4+ increased the chlorophyll content (Chl) and N metabolic enzyme activity, decreased the abscisic acid (ABA) content, and improved stomatal conductance (Gs).”
t0“rice”
Claim · model-written summary
T-43 had relatively high IAA, chlorophyll and stomatal conductance.
- Taxon
- riceOryza sativat0
- Material
- T-43e0
- Outcome
- indole-3-acetic acid (IAA), Chl a + b, and Gse0
- Direction
- highe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“T-43 presented relatively high levels of indole-3-acetic acid (IAA), Chl a + b, and Gs”
t0“rice”
Claim · model-written summary
T-43 had a relatively high photosynthetic rate.
- Taxon
- riceOryza sativat0
- Material
- T-43e0
- Outcome
- photosynthetic rate (Pn)e0
- Direction
- highe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“T-43 presented relatively high levels of indole-3-acetic acid (IAA), Chl a + b, and Gs, and a relatively high photosynthetic rate (Pn)”
t0“rice”
Claim · model-written summary
LX-3 had increased ABA levels.
- Taxon
- riceOryza sativat0
- Material
- LX-3e0
- Outcome
- ABA levelse0
- Direction
- increasede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“LX-3 presented increased ABA levels and reduced Chl a + b, and Gs.”
t0“rice”
Claim · model-written summary
LX-3 had reduced chlorophyll and stomatal conductance.
- Taxon
- riceOryza sativat0
- Material
- LX-3e0
- Outcome
- Chl a + b, and Gse0
- Direction
- reducede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“LX-3 presented increased ABA levels and reduced Chl a + b, and Gs.”
t0“rice”
Claim · model-written summary
Under ammonium, IAA correlated positively with Chl b, Gs and Fv/Fm.
- Taxon
- riceOryza sativat0
- Treatment
- NH4+e0
- Compound
- IAAe0
- Outcome
- Chl b, Gs, and Fv/Fme0
- Direction
- positively correlatede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“under NH4+, IAA was positively correlated with Chl b, Gs, and Fv/Fm”
t0“rice”
Claim · model-written summary
Under ammonium, ABA correlated negatively with Y(II) and chlorophyll.
- Taxon
- riceOryza sativat0
- Compound
- ABAe0
- Outcome
- Y(II), and Chl a + be0
- Direction
- negatively correlatede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“ABA was negatively correlated with Y(II), and Chl a + b”
t0“rice”
Claim · model-written summary
Chlorophyll decreased in urea and nitrate treatments.
- Taxon
- riceOryza sativat0
- Treatment
- Urea and NO3− treatmentse0
- Outcome
- Chl contentse0
- Direction
- decreasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The Chl contents decreased, and the ABA and Chl a/b increased in the Urea and NO3− treatments”
t0“rice”
Claim · model-written summary
ABA and chlorophyll a/b increased in urea and nitrate treatments.
- Taxon
- riceOryza sativat0
- Treatment
- Urea and NO3− treatmentse0
- Outcome
- ABA and Chl a/be0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The Chl contents decreased, and the ABA and Chl a/b increased in the Urea and NO3− treatments”
t0“rice”
Claim · model-written summary
The model assigned ammonium a higher yield contribution than urea and nitrate.
- Taxon
- riceOryza sativat0
- Treatment
- NH4+e0
- Outcome
- contribution of NH4+e0
- Direction
- increasinge0
- Value
- 0.714e0
- Qualifier
- 0.614e0
- Comparator
- Ureae0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“increasing the contribution of NH4+ (GoF = 0.714) to yield when compared to the yields in the Urea (0.614) and NO3− (0.594)”
t0“rice”
Claim · model-written summary
The authors conclude ammonium enhances photochemical efficiency and antioxidant capacity.
- Taxon
- riceOryza sativat0
- Treatment
- NH4+e0
- Outcome
- photochemical efficiency, antioxidant capacitye0
- Qualifier
- regulates hormone balancee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“NH4+ synergistically enhances Chl content, photochemical efficiency, antioxidant capacity, and regulates hormone balance”
t0“rice”
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