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Background and aims <p><i>Reaumuria soongorica,</i> a perennial halophytic semi-shrub native to arid and saline regions of northwestern China, exhibits remarkable tolerance to drought and salinity. Previous studies showed that salt or drought stress increases salt secretion via salt glands, yet the plant maintains stable tissue water content, suggesting a unique internal water regulation mechanism.</p> Methods <p>Six-week-old seedlings were grown under control (70% FWC), low salt (70% FWC +&#xa0;50&#xa0;mM NaCl), high salt (70% FWC +&#xa0;300&#xa0;mM NaCl), drought (30% FWC), or drought + salt (30% FWC +&#xa0;50&#xa0;mM NaCl). Physiological traits related to water balance and ion distribution were assessed. Three aquaporin genes (<i>RsPIP2;1</i>, <i>RsPIP2;7</i>, and <i>RsTIP1;3</i>) were cloned and analyzed for expression patterns, subcellular localization, and water transport activity.</p> Results <p>Under stress conditions, <i>R. soongorica</i> maintained a distinct water potential gradient (Ψ<sub>root</sub> &gt; Ψ<sub>leaf</sub> &gt;Ψ<sub>stem</sub>). This gradient facilitated water uptake from soil and internal redistribution between tissues, particularly from leaves to stems, sustaining water homeostasis. Exogenous NaCl enhanced osmotic adjustment and stabilized this internal water status without significantly improving dry biomass accumulation under drought. The three aquaporins showed tissue-specific and stress-responsive expression, consistent with roles in transmembrane water movement and maintenance of the water potential gradient.</p> Conclusions <p>These findings highlight a proposed stem-centered water regulation hypothesis integrating ion accumulation, osmotic adjustment, and aquaporin-mediated water transport. These mechanisms contribute to stress tolerance and offer potential targets for improving crop resilience.</p>

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Mechanisms underlying water balance regulation in Reaumuria soongorica under salt and drought conditions

  • 期刊论文

  • 发表日期：

    2026年7月15日

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  • Shan Wang,
  • Jia-Hao Su,
  • Shan Feng,
  • Ai-Ke Bao

摘要

Background and aims

Reaumuria soongorica, a perennial halophytic semi-shrub native to arid and saline regions of northwestern China, exhibits remarkable tolerance to drought and salinity. Previous studies showed that salt or drought stress increases salt secretion via salt glands, yet the plant maintains stable tissue water content, suggesting a unique internal water regulation mechanism.

Methods

Six-week-old seedlings were grown under control (70% FWC), low salt (70% FWC + 50 mM NaCl), high salt (70% FWC + 300 mM NaCl), drought (30% FWC), or drought + salt (30% FWC + 50 mM NaCl). Physiological traits related to water balance and ion distribution were assessed. Three aquaporin genes (RsPIP2;1, RsPIP2;7, and RsTIP1;3) were cloned and analyzed for expression patterns, subcellular localization, and water transport activity.

Results

Under stress conditions, R. soongorica maintained a distinct water potential gradient (Ψroot > Ψleaf >Ψstem). This gradient facilitated water uptake from soil and internal redistribution between tissues, particularly from leaves to stems, sustaining water homeostasis. Exogenous NaCl enhanced osmotic adjustment and stabilized this internal water status without significantly improving dry biomass accumulation under drought. The three aquaporins showed tissue-specific and stress-responsive expression, consistent with roles in transmembrane water movement and maintenance of the water potential gradient.

Conclusions

These findings highlight a proposed stem-centered water regulation hypothesis integrating ion accumulation, osmotic adjustment, and aquaporin-mediated water transport. These mechanisms contribute to stress tolerance and offer potential targets for improving crop resilience.