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<p>Nitrogen plays crucial roles in photosynthesis and crop yields. In 2024, a field experiment was conducted with various nitrogen treatments (N0, N60, N120, N150, N180, N240, and N300) to evaluate the impact on photosystem activity, dry matter accumulation (DMA), and taproot development in sugar beet. The results show that nitrogen fertilization significantly reduced the fluorescence at the K-, J-, and I-steps, compared to controls, while enhancing absorption per active reaction center, trapped energy flux per active reaction center, and electron transport per active reaction center. In addition, maximum photochemical efficiency (<i>φ</i>Po), photochemical energy conversion efficiency (<i>φ</i>Eo), and the probability of captured excitation energy being transferred to the electron transport chain (<i>ψ</i>o) showed a single-peak pattern with increasing nitrogen, with a maximum value of <i>ψ</i>o with the N180 treatment on July 22. During the growth stage, DMA and the rate thereof followed a single-peak trend, accompanied by increased root/shoot ratios and reduced source–sink activity. As nitrogen levels increased, DMA and the rate thereof increased during the early to mid-growth stages, while total and aboveground DMA rates peaked and subsequently declined during the sugar accumulation stage. Relative to N0, nitrogen application accelerated the rapid taproot DMA onset and the timing of the maximum accumulation rate, which is increased significantly. The N180 treatment resulted in the highest accumulation rate, with an increase of 43.48% relative to that without treatment. Increased nitrogen also increased the yields by 8.9–48.5%; the highest sugar yield, with the N180 treatment, surpassed those of other treatments by 5.55–40.94%. Optimal nitrogen application (N180) enhanced the PSII reaction center activity, improved the electron transport efficiency and reduced the non-photochemical energy dissipation. This increased the total DMA, optimized the source–sink balance, and effectively regulated the key parameters of taproot DMA, ultimately leading to increased sugar beet yields.</p>

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Effects of Optimized Nitrogen Fertilizer Application on Chlorophyll Fluorescence Characteristics and Dry Matter Accumulation in Sugar Beet

  • 期刊论文

  • 发表日期：

    2025年6月9日

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  • Shi-Feng Dong,
  • Lei Wei,
  • Xing-Bo Tong,
  • Yi-Na Zhang,
  • Rong-Li Jia,
  • Xu-Ming Xing,
  • Shu-De Shi

摘要

Nitrogen plays crucial roles in photosynthesis and crop yields. In 2024, a field experiment was conducted with various nitrogen treatments (N0, N60, N120, N150, N180, N240, and N300) to evaluate the impact on photosystem activity, dry matter accumulation (DMA), and taproot development in sugar beet. The results show that nitrogen fertilization significantly reduced the fluorescence at the K-, J-, and I-steps, compared to controls, while enhancing absorption per active reaction center, trapped energy flux per active reaction center, and electron transport per active reaction center. In addition, maximum photochemical efficiency (φPo), photochemical energy conversion efficiency (φEo), and the probability of captured excitation energy being transferred to the electron transport chain (ψo) showed a single-peak pattern with increasing nitrogen, with a maximum value of ψo with the N180 treatment on July 22. During the growth stage, DMA and the rate thereof followed a single-peak trend, accompanied by increased root/shoot ratios and reduced source–sink activity. As nitrogen levels increased, DMA and the rate thereof increased during the early to mid-growth stages, while total and aboveground DMA rates peaked and subsequently declined during the sugar accumulation stage. Relative to N0, nitrogen application accelerated the rapid taproot DMA onset and the timing of the maximum accumulation rate, which is increased significantly. The N180 treatment resulted in the highest accumulation rate, with an increase of 43.48% relative to that without treatment. Increased nitrogen also increased the yields by 8.9–48.5%; the highest sugar yield, with the N180 treatment, surpassed those of other treatments by 5.55–40.94%. Optimal nitrogen application (N180) enhanced the PSII reaction center activity, improved the electron transport efficiency and reduced the non-photochemical energy dissipation. This increased the total DMA, optimized the source–sink balance, and effectively regulated the key parameters of taproot DMA, ultimately leading to increased sugar beet yields.