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<p>Under increasing frequency of extreme climate events, plant adaptation to alternating drought–rewatering stress is critical. <i>Kengyilia hirsuta</i>, a pioneer forage grass in alpine desert ecosystems, relies on rhizosheath formation for drought resistance. This study conducted indoor pot experiments with six water treatments: three drought–rewatering cycles (W1–W3, re‑watered to 10%, 25%, and 40% of field capacity, FC) and three sustained drought levels (W4–W6, maintained at 10%, 25%, and 40% FC). Root architecture, biomass allocation, arbuscular mycorrhizal fungi (AMF) colonization, and rhizosheath formation were examined over three successive 7‑day periods (T1–T3). Results revealed dynamic responses of rhizosheath accumulation to water regimes: maintained 25% FC (W5) significantly promoted rhizosheath biomass, maintained 40% FC (W6) enhanced early‑stage development, and re‑watering to 10% FC (W1) boosted later‑stage formation. AMF colonization increased progressively, with total colonization rising from 41.51% at T1 (day 7) to 61.40% at T3 (day 21). The W5 treatment consistently exhibited the highest vesicle, arbuscule, and hyphal colonization, along with increased soil spore density and hyphal density by T3. Root morphological traits—including tip number, volume, hair length, and hair density—also peaked under W5. Structural equation modelling identified AMF colonization (total effect: –0.90) and root hair traits (total effect: +0.80) as pivotal regulators of rhizosheath formation. This negative total effect of AMF colonization does not indicate overall inhibition, but rather reflects the feedback regulation intensity mediated by microbial competition and the carbon allocation trade-off within the plant-fungal symbiosis under resource-limited conditions. These factors interact through biomass allocation, root architecture, and soil microenvironment, forming a multidimensional adaptive network. These findings elucidate the ecophysiological mechanisms of plant–AMF collaboration in rhizosheath formation under water fluctuation, supporting the selection of stress‑tolerant grasses for restoring desertified grasslands.</p>

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Mechanisms underlying rhizosheath dynamics in Kengyilia hirsuta in response to alternating drought and rewatering

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年4月24日

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  • Yutao Yuan,
  • Li Wu,
  • Jianhong Zhang,
  • Chen Chen,
  • Qingping Zhou,
  • Youjun Chen

摘要

Under increasing frequency of extreme climate events, plant adaptation to alternating drought–rewatering stress is critical. Kengyilia hirsuta, a pioneer forage grass in alpine desert ecosystems, relies on rhizosheath formation for drought resistance. This study conducted indoor pot experiments with six water treatments: three drought–rewatering cycles (W1–W3, re‑watered to 10%, 25%, and 40% of field capacity, FC) and three sustained drought levels (W4–W6, maintained at 10%, 25%, and 40% FC). Root architecture, biomass allocation, arbuscular mycorrhizal fungi (AMF) colonization, and rhizosheath formation were examined over three successive 7‑day periods (T1–T3). Results revealed dynamic responses of rhizosheath accumulation to water regimes: maintained 25% FC (W5) significantly promoted rhizosheath biomass, maintained 40% FC (W6) enhanced early‑stage development, and re‑watering to 10% FC (W1) boosted later‑stage formation. AMF colonization increased progressively, with total colonization rising from 41.51% at T1 (day 7) to 61.40% at T3 (day 21). The W5 treatment consistently exhibited the highest vesicle, arbuscule, and hyphal colonization, along with increased soil spore density and hyphal density by T3. Root morphological traits—including tip number, volume, hair length, and hair density—also peaked under W5. Structural equation modelling identified AMF colonization (total effect: –0.90) and root hair traits (total effect: +0.80) as pivotal regulators of rhizosheath formation. This negative total effect of AMF colonization does not indicate overall inhibition, but rather reflects the feedback regulation intensity mediated by microbial competition and the carbon allocation trade-off within the plant-fungal symbiosis under resource-limited conditions. These factors interact through biomass allocation, root architecture, and soil microenvironment, forming a multidimensional adaptive network. These findings elucidate the ecophysiological mechanisms of plant–AMF collaboration in rhizosheath formation under water fluctuation, supporting the selection of stress‑tolerant grasses for restoring desertified grasslands.