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Background <p>Under global climate change, prolonged rainfall intervals and intensified single rainfall events in karst rocky desertification areas, together with increased karst fissure thickness, significantly affect plant seedling growth and physiology. This study used a two-factor block experiment to explore the effects of different rainfall intervals and karst habitats on the photosynthetic physiology of two-year-old <i>Fraxinus malacophylla</i> seedlings.</p> Results <p>The results showed that under the same rainfall interval, the carbon (C), nitrogen (N), phosphorus (P) content, photosynthetic pigment content, fluorescence parameters, and photosynthetic gas parameters of <i>F. malacophylla</i> seedlings showed a trend of first increasing and then decreasing with the increase of karst fissures. Under the I<sub>6d</sub>S<sub>1/2</sub> treatment, the maximum net photosynthetic rate, light saturation point, and light compensation point reached 8.143, 1408.190, and 71.474 µmol·m⁻²·s⁻¹, respectively, with a maximum CO₂ saturation point of 1571.580 µmol·m⁻²·s⁻¹. Biomass allocation followed the order of stem &gt; leaf &gt; root in the S<sub>0</sub> habitat, whereas it showed the order of root &gt; stem &gt; leaf in the S<sub>1/2</sub> and S<sub>3/4</sub> habitats. At I<sub>3d</sub> and I<sub>6d</sub> rainfall intervals, SOD, POD, and SPC activities rose with increasing karst thickness, while an opposite pattern was found at I<sub>9d</sub>. Specifically, the prolonged rainfall interval (I<sub>9d</sub>) inhibits the growth of <i>F. malacophylla</i> seedlings, mainly because the long-term water deficit exceeds the osmotic regulation limit of the seedlings and causes an imbalance in the antioxidant system, rather than a single collapse of the antioxidant system.</p> Conclusions <p>In summary, the <i>F. malacophylla</i> seedlings grew best under I<sub>6d</sub>S<sub>1/2</sub> treatment, and prolonged rainfall intervals inhibited the growth of <i>F. malacophylla</i> seedlings. This study suggests that shallow-soil karst rocky desertification areas can serve as suitable habitats for <i>F. malacophylla</i> seedlings, thereby providing a theoretical basis and technical support for vegetation restoration, the cultivation of <i>F. malacophylla</i> seedlings, and the maintenance of ecosystem stability in karst rocky desertification regions.</p> Graphical Abstract <p></p>

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Strategies of photosynthetic physiology in response to karst habitats and rainfall allocation have maintained the morphology and function of Fraxinus malacophylla seedlings

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年7月1日

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  • Shaojie Zheng,
  • Lehao Li,
  • Qize Zhao,
  • Tao Zhang,
  • Rongxin Gou,
  • Lin Wang,
  • Yuanyou Wang,
  • Shunrou Shi,
  • Yaoyi Chen,
  • Chengmeng Zhang,
  • Qiong Dong

摘要

Background

Under global climate change, prolonged rainfall intervals and intensified single rainfall events in karst rocky desertification areas, together with increased karst fissure thickness, significantly affect plant seedling growth and physiology. This study used a two-factor block experiment to explore the effects of different rainfall intervals and karst habitats on the photosynthetic physiology of two-year-old Fraxinus malacophylla seedlings.

Results

The results showed that under the same rainfall interval, the carbon (C), nitrogen (N), phosphorus (P) content, photosynthetic pigment content, fluorescence parameters, and photosynthetic gas parameters of F. malacophylla seedlings showed a trend of first increasing and then decreasing with the increase of karst fissures. Under the I6dS1/2 treatment, the maximum net photosynthetic rate, light saturation point, and light compensation point reached 8.143, 1408.190, and 71.474 µmol·m⁻²·s⁻¹, respectively, with a maximum CO₂ saturation point of 1571.580 µmol·m⁻²·s⁻¹. Biomass allocation followed the order of stem > leaf > root in the S0 habitat, whereas it showed the order of root > stem > leaf in the S1/2 and S3/4 habitats. At I3d and I6d rainfall intervals, SOD, POD, and SPC activities rose with increasing karst thickness, while an opposite pattern was found at I9d. Specifically, the prolonged rainfall interval (I9d) inhibits the growth of F. malacophylla seedlings, mainly because the long-term water deficit exceeds the osmotic regulation limit of the seedlings and causes an imbalance in the antioxidant system, rather than a single collapse of the antioxidant system.

Conclusions

In summary, the F. malacophylla seedlings grew best under I6dS1/2 treatment, and prolonged rainfall intervals inhibited the growth of F. malacophylla seedlings. This study suggests that shallow-soil karst rocky desertification areas can serve as suitable habitats for F. malacophylla seedlings, thereby providing a theoretical basis and technical support for vegetation restoration, the cultivation of F. malacophylla seedlings, and the maintenance of ecosystem stability in karst rocky desertification regions.

Graphical Abstract