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<p>Nitrogen (N) is an important nutrient used to enhance crop productivity; however, its excessive use leads to a significant increase in nitrous oxide (N₂O) emissions. Melatonin (MT) is acknowledged as important player to mitigate the toxic impacts of abiotic stress.&#xa0;However, its impact on crop production and N₂O is rarely studied. Therefore, this study investigated the impacts of MT on photosynthetic efficiency, assimilate accumulation, rice productivity, and N₂O emissions under different levels of N supply. This two-year study was conducted with following treatments; N1: 150 kg N ha−1, N2: 120 kg N ha−1, N3: 90 kg N ha−1, MT: foliar spray of MT (100 µmol L−1), N1 + MT: 150 kg N ha−1 + foliar spray of MT (100 µmol L−1), N2 + MT: 120 kg N ha−1 + foliar spray of MT (100 µmol L−1), N3 + MT: 90 kg N ha−1 + foliar spray of MT (100 µmol L−1). Foliar supply of MT significantly decreased the N₂O emissions under 150 kg ha−1 N (49.51%), 120 kg ha−1 N (61.84%) and 90 kg ha−1 N (73%) compared to sole N application without MT application during both years. The results showed that foliar spray of MT significantly enhanced the rice grain yield under different N supply levels. Melatonin supply significantly increased the leaf photosynthetic rate and decreased the intercellular CO2 concentration, leading to better assimilate production and grain yield. The foliar MT supply under reduced N application (N2 and N3) treatments also enhanced the activities of stem and grain ADP-glucose pyrophosphorylase (AGP), starch synthase (StS), α-amylase, β-amylase, resulting in better grain yield in 2023 (29.17% and 21.61%) and 2024 (31.48% and 23.33%) as compared to treatments without MT application. Melatonin spray under reduced N supply also significantly increased the expression of stem and grain genes (OsSUT1, OsSUT2, OsSWEET4, and OsSWEET11) linked with sucrose phloem unloading in the stem and grains, leading to better grain yield under reduced N supply. Furthermore, N1 + MT and N2 + MT treatments produced same yield during both years indicating that 20% N can be saved by adopting this practice. Therefore, foliar spray of MT under reduced N can increase rice productivity and decrease N₂O emissions by enhancing photosynthetic efficiency, starch metabolism enzymes, gene expression, and dry matter production.</p>

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Melatonin with Reduced Nitrogen Enhances Rice Productivity and Lowers Nitrous Oxide Emissions by Stimulating Carbon Assimilation

  • 期刊论文

  • 发表日期：

    2026年5月8日

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  • Daji Li,
  • Muhammad Naeem Sattar,
  • Abdul Ghafoor

摘要

Nitrogen (N) is an important nutrient used to enhance crop productivity; however, its excessive use leads to a significant increase in nitrous oxide (N₂O) emissions. Melatonin (MT) is acknowledged as important player to mitigate the toxic impacts of abiotic stress. However, its impact on crop production and N₂O is rarely studied. Therefore, this study investigated the impacts of MT on photosynthetic efficiency, assimilate accumulation, rice productivity, and N₂O emissions under different levels of N supply. This two-year study was conducted with following treatments; N1: 150 kg N ha−1, N2: 120 kg N ha−1, N3: 90 kg N ha−1, MT: foliar spray of MT (100 µmol L−1), N1 + MT: 150 kg N ha−1 + foliar spray of MT (100 µmol L−1), N2 + MT: 120 kg N ha−1 + foliar spray of MT (100 µmol L−1), N3 + MT: 90 kg N ha−1 + foliar spray of MT (100 µmol L−1). Foliar supply of MT significantly decreased the N₂O emissions under 150 kg ha−1 N (49.51%), 120 kg ha−1 N (61.84%) and 90 kg ha−1 N (73%) compared to sole N application without MT application during both years. The results showed that foliar spray of MT significantly enhanced the rice grain yield under different N supply levels. Melatonin supply significantly increased the leaf photosynthetic rate and decreased the intercellular CO2 concentration, leading to better assimilate production and grain yield. The foliar MT supply under reduced N application (N2 and N3) treatments also enhanced the activities of stem and grain ADP-glucose pyrophosphorylase (AGP), starch synthase (StS), α-amylase, β-amylase, resulting in better grain yield in 2023 (29.17% and 21.61%) and 2024 (31.48% and 23.33%) as compared to treatments without MT application. Melatonin spray under reduced N supply also significantly increased the expression of stem and grain genes (OsSUT1, OsSUT2, OsSWEET4, and OsSWEET11) linked with sucrose phloem unloading in the stem and grains, leading to better grain yield under reduced N supply. Furthermore, N1 + MT and N2 + MT treatments produced same yield during both years indicating that 20% N can be saved by adopting this practice. Therefore, foliar spray of MT under reduced N can increase rice productivity and decrease N₂O emissions by enhancing photosynthetic efficiency, starch metabolism enzymes, gene expression, and dry matter production.