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<p>Soil salinization is a widespread environmental problem that enhancing plant salt tolerance and increasing plant biomass through agronomic measures is an urgent problem to be addressed. In this study, one-year-old ‘Gui 109’ mulberry (<i>Morus spp</i>.) seedlings, used for forage, were employed as experimental materials in a hydroponic system. The effects of different nitrogen application levels (0, 2, 6, 10, and 16 mmol·L<sup>−1</sup>) on seedling growth, photosynthetic parameters, and physiological traits were investigated under varying salt stress levels (0, 0.1%, and 0.2% NaCl). The results showed that under salt stress, photosynthetic pigments, <i>P</i><sub><i>n</i></sub>, <i>G</i><sub><i>s</i></sub>, and <i>T</i><sub><i>r</i></sub> increased initially and then declined with increasing nitrogen supply, whereas <i>C</i><sub><i>i</i></sub> exhibited the opposite trend.With increasing salinity, these parameters showed a similar biphasic pattern, and inhibition was more pronounced at 0.2% NaCl during later stages.Under control conditions (CK),Na⁺ content decreased with increasing nitrogen at the early stage but displayed a decline–increase pattern later.Under salt stress, Na⁺ content displayed a decreasing–increasing pattern with rising nitrogen levels and increased progressively with higher salinity.The contents of K⁺, Ca<sup>2</sup>⁺, and Mg<sup>2</sup>⁺ in leaves and roots increased initially and then declined with increasing nitrogen supply and prolonged stress duration. Increasing salinity significantly reduced K⁺ and Ca<sup>2</sup>⁺ levels in both tissues.Correlation analysis revealed significant positive relationships among photosynthetic pigments. Net photosynthetic rate was positively correlated with stomatal conductance (0.91) and negatively correlated with intercellular CO₂ concentration (− 0.91). K⁺ was positively associated with photosynthetic performance, whereas Na⁺ showed negative associations. Overall, salt stress suppressed photosynthesis and disturbed ion uptake and transport. Moderate nitrogen improved salt tolerance by enhancing photosynthetic efficiency and ion regulation, whereas excessive nitrogen aggravated salt damage.</p>

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Nitrogen modulates photosynthetic physiology and ion homeostasis in forage mulberry (Morus spp) seedlings under salt stress

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年3月11日

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  • Jie Tian,
  • Chan Du,
  • Xiangting Cao,
  • Yifan Zhang,
  • Jingyan Yang,
  • Yibo Wu,
  • Hongjiao Li

摘要

Soil salinization is a widespread environmental problem that enhancing plant salt tolerance and increasing plant biomass through agronomic measures is an urgent problem to be addressed. In this study, one-year-old ‘Gui 109’ mulberry (Morus spp.) seedlings, used for forage, were employed as experimental materials in a hydroponic system. The effects of different nitrogen application levels (0, 2, 6, 10, and 16 mmol·L−1) on seedling growth, photosynthetic parameters, and physiological traits were investigated under varying salt stress levels (0, 0.1%, and 0.2% NaCl). The results showed that under salt stress, photosynthetic pigments, Pn, Gs, and Tr increased initially and then declined with increasing nitrogen supply, whereas Ci exhibited the opposite trend.With increasing salinity, these parameters showed a similar biphasic pattern, and inhibition was more pronounced at 0.2% NaCl during later stages.Under control conditions (CK),Na⁺ content decreased with increasing nitrogen at the early stage but displayed a decline–increase pattern later.Under salt stress, Na⁺ content displayed a decreasing–increasing pattern with rising nitrogen levels and increased progressively with higher salinity.The contents of K⁺, Ca2⁺, and Mg2⁺ in leaves and roots increased initially and then declined with increasing nitrogen supply and prolonged stress duration. Increasing salinity significantly reduced K⁺ and Ca2⁺ levels in both tissues.Correlation analysis revealed significant positive relationships among photosynthetic pigments. Net photosynthetic rate was positively correlated with stomatal conductance (0.91) and negatively correlated with intercellular CO₂ concentration (− 0.91). K⁺ was positively associated with photosynthetic performance, whereas Na⁺ showed negative associations. Overall, salt stress suppressed photosynthesis and disturbed ion uptake and transport. Moderate nitrogen improved salt tolerance by enhancing photosynthetic efficiency and ion regulation, whereas excessive nitrogen aggravated salt damage.