Abstract
Context Rice is one of the world's most important food crops, and the excessive use of fertilizers to achieve high rice yields has led to global environmental concerns. Therefore, it is critical to reduce nitrogen fertilizer input, a problem for which nano carbon dots (NCD) provide a promising solution. However, few studies have examined the effect of NCD on rice yield formation under reduced nitrogen input conditions. Objectives The aim of this study is to evaluate the effects of NCD on the photosynthetic characteristics, accumulation and translocation of stem assimilates, and yield of rice under reduced nitrogen conditions. Methods A two-year field experiment was conducted on rice using two varieties, Yongyou2640 and Y liangyou2, with five treatments: N1 (270 kg N ha −1 ), N2 (216 kg N ha −1 ), N3 (162 kg N ha −1 ), CN2 (216 kg N ha −1 +foliar application of NCD), and CN3 (162 kg N ha −1 + foliar application of NCD). Leaf photosynthetic enzyme activity, stem and grain starch synthesis-related enzyme activity, sucrose translocation-related enzyme and gene expression, and yield and yield components were measured at five time points from the jointing stage to maturity. Results Under the condition of reducing nitrogen fertilizer by 40 %, the foliar application of NCD could significantly increase rice yield, with average increases of 13.2 % and 12.3 % for both varieties in 2022 and 2023, respectively, reaching the yield achieved with normal nitrogen levels. The foliar application of NCD significantly increased the leaf photosynthetic rate by increasing rubisco enzyme activity, resulting in a 8.5–61.5 % increase in the photosynthetic rate for both varieties at different growth stages across the two years. In addition, the foliar application of NCD prior to heading increased the stem activity of ADP-glucose pyrophosphorylase (AGP) and starch synthase (StS), thereby increasing the accumulation of NSC in the stems before flowering. The average increases for both varieties were 21.2 % and 17.8 % in 2022 and 2023, respectively. After heading, the activities of α-amylase, β-amylase, and sucrose phosphate synthase (SPS) in the stems, as well as the activities of AGP, StS, and cell wall invertase in the grains, were significantly increased. The expression of key genes involved in sucrose phloem loading in the stem, OsSUTs and OsSWEETs, and genes related to sucrose phloem unloading in the grains, OsSUTs , OsSWEETs , and OsCINs, were upregulated, thereby promoting the translocation of assimilates from the stems to the grains, which improved the grain filling percentage and consequently increased the grain yield under conditions of nitrogen deficiency. Conclusion In summary, under conditions of nitrogen deficiency, the foliar application of NCD to rice can increase the activities of photosynthetic enzymes, starch metabolism enzymes in stems and grains, and sucrose translocation-related enzymes; increase sucrose translocation-related gene expression; regulate the accumulation and translocation of assimilates; and improve grain filling and grain yield, and also increase economic profit.
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Claims 15
Claim · model-written summary
Foliar NCD increased rice yield under 40% reduced nitrogen by 13.2% in 2022.
- Taxon
- rice
Oryza sativat0 - Treatment
- foliar application of NCDe0
- Outcome
- rice yielde0
- Direction
- increasee0
- Value
- 13.2 %e0
- Qualifier
- 2022e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Under the condition of reducing nitrogen fertilizer by 40 %, the foliar application of NCD could significantly increase rice yield, with average increases of 13.2 % and 12.3 % for both varieties in 2022 and 2023, respectively”
t0“rice”
Claim · model-written summary
Foliar NCD increased rice yield under 40% reduced nitrogen by 12.3% in 2023.
- Taxon
- riceOryza sativat0
- Treatment
- foliar application of NCDe0
- Outcome
- rice yielde0
- Direction
- increasee0
- Value
- 12.3 %e0
- Qualifier
- 2023e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Under the condition of reducing nitrogen fertilizer by 40 %, the foliar application of NCD could significantly increase rice yield, with average increases of 13.2 % and 12.3 % for both varieties in 2022 and 2023, respectively”
t0“rice”
Claim · model-written summary
Yield with NCD under reduced nitrogen reached the yield under normal nitrogen.
- Taxon
- riceOryza sativat0
- Treatment
- foliar application of NCDe1
- Outcome
- yielde0
- Direction
- reachinge0
- Comparator
- normal nitrogen levelse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“reaching the yield achieved with normal nitrogen levels.”
e1“the foliar application of NCD to rice”
t0“rice”
Claim · model-written summary
NCD increased photosynthetic rate by 8.5–61.5% across growth stages.
- Taxon
- riceOryza sativat0
- Treatment
- foliar application of NCDe0
- Outcome
- leaf photosynthetic ratee0
- Direction
- increasede0
- Value
- 8.5–61.5 %e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The foliar application of NCD significantly increased the leaf photosynthetic rate by increasing rubisco enzyme activity, resulting in a 8.5–61.5 % increase in the photosynthetic rate for both varieties at different growth stages across the two years.”
t0“rice”
Claim · model-written summary
NCD increased rubisco enzyme activity.
- Taxon
- riceOryza sativat0
- Treatment
- foliar application of NCDe0
- Gene
- rubiscoe0
- Outcome
- rubisco enzyme activitye0
- Direction
- increasinge0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The foliar application of NCD significantly increased the leaf photosynthetic rate by increasing rubisco enzyme activity”
t0“rice”
Claim · model-written summary
Before heading, NCD increased stem AGP and StS activities.
- Taxon
- riceOryza sativat0
- Organ / stage
- steme0
- Treatment
- foliar application of NCDe0
- Outcome
- stem activity of ADP-glucose pyrophosphorylase (AGP) and starch synthase (StS)e0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the foliar application of NCD prior to heading increased the stem activity of ADP-glucose pyrophosphorylase (AGP) and starch synthase (StS)”
t0“rice”
Claim · model-written summary
Before flowering, NCD increased stem NSC accumulation by 21.2% in 2022.
- Taxon
- riceOryza sativat0
- Treatment
- foliar application of NCDe1
- Outcome
- accumulation of NSC in the stemse0
- Direction
- increasinge0
- Value
- 21.2 %e0
- Qualifier
- 2022e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“increasing the accumulation of NSC in the stems before flowering. The average increases for both varieties were 21.2 % and 17.8 % in 2022 and 2023, respectively.”
e1“the foliar application of NCD to rice”
t0“rice”
Claim · model-written summary
Before flowering, NCD increased stem NSC accumulation by 17.8% in 2023.
- Taxon
- riceOryza sativat0
- Treatment
- foliar application of NCDe1
- Outcome
- accumulation of NSC in the stemse0
- Direction
- increasinge0
- Value
- 17.8 %e0
- Qualifier
- 2023e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“increasing the accumulation of NSC in the stems before flowering. The average increases for both varieties were 21.2 % and 17.8 % in 2022 and 2023, respectively.”
e1“the foliar application of NCD to rice”
t0“rice”
Claim · model-written summary
After heading, NCD increased stem α-amylase, β-amylase, and SPS activities.
- Taxon
- riceOryza sativat0
- Treatment
- foliar application of NCDe1
- Outcome
- activities of α-amylase, β-amylase, and sucrose phosphate synthase (SPS) in the stemse0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“After heading, the activities of α-amylase, β-amylase, and sucrose phosphate synthase (SPS) in the stems, as well as the activities of AGP, StS, and cell wall invertase in the grains, were significantly increased.”
e1“the foliar application of NCD to rice”
t0“rice”
Claim · model-written summary
After heading, NCD increased grain AGP, StS, and cell wall invertase activities.
- Taxon
- riceOryza sativat0
- Treatment
- foliar application of NCDe1
- Outcome
- activities of AGP, StS, and cell wall invertase in the grainse0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the activities of AGP, StS, and cell wall invertase in the grains, were significantly increased.”
e1“the foliar application of NCD to rice”
t0“rice”
Claim · model-written summary
Stem sucrose-loading genes OsSUTs and OsSWEETs were upregulated.
- Taxon
- riceOryza sativat0
- Treatment
- foliar application of NCDe1
- Gene
- OsSUTs and OsSWEETse0
- Outcome
- expression of key genes involved in sucrose phloem loading in the steme0
- Direction
- upregulatede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The expression of key genes involved in sucrose phloem loading in the stem, OsSUTs and OsSWEETs, and genes related to sucrose phloem unloading in the grains, OsSUTs , OsSWEETs , and OsCINs, were upregulated”
e1“the foliar application of NCD to rice”
t0“rice”
Claim · model-written summary
Grain sucrose-unloading genes OsSUTs, OsSWEETs, and OsCINs were upregulated.
- Taxon
- riceOryza sativat0
- Treatment
- foliar application of NCDe1
- Gene
- OsSUTs , OsSWEETs , and OsCINse0
- Outcome
- genes related to sucrose phloem unloading in the grainse0
- Direction
- upregulatede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“genes related to sucrose phloem unloading in the grains, OsSUTs , OsSWEETs , and OsCINs, were upregulated”
e1“the foliar application of NCD to rice”
t0“rice”
Claim · model-written summary
NCD promoted assimilate transfer from stems to grains.
- Taxon
- riceOryza sativat0
- Treatment
- foliar application of NCDe1
- Outcome
- translocation of assimilates from the stems to the grainse0
- Direction
- promotinge0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“promoting the translocation of assimilates from the stems to the grains”
e1“the foliar application of NCD to rice”
t0“rice”
Claim · model-written summary
NCD improved grain filling percentage under nitrogen deficiency.
- Taxon
- riceOryza sativat0
- Treatment
- foliar application of NCDe1
- Outcome
- grain filling percentagee0
- Direction
- improvede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“improved the grain filling percentage and consequently increased the grain yield under conditions of nitrogen deficiency”
e1“the foliar application of NCD to rice”
t0“rice”
Claim · model-written summary
NCD increased economic profit under nitrogen deficiency.
- Taxon
- riceOryza sativat0
- Treatment
- foliar application of NCDe1
- Outcome
- economic profite0
- Direction
- increasee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“also increase economic profit.”
e1“the foliar application of NCD to rice”
t0“rice”
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