Limited Benefits of Funneliformis mosseae for Hordeum jubatum Under Cold Stress: An Anatomical Perspective

Plants in high latitude regions frequently experience cold stress, which strongly constrains plant growth and development. Although arbuscular mycorrhizal fungi (AMF) can form beneficial symbiotic relationships with plants, their role in mediating anatomical adaptations under different temperature regimes remains insufficiently understood. In this study, we investigated how inoculation with the AMF Funneliformis mosseae influences anatomical responses in Hordeum jubatum under contrasting temperature conditions using detailed microscopic analysis. Under normal temperature conditions, AMF inoculation promoted significant improvements in plant anatomical structures. Stomatal dimensions including length, width and area showed marked increases alongside elevated stomatal density. Leaf tissues exhibited enhanced development, particularly in vascular and epidermal components, while root systems displayed an expanded radius, greater cortical thickness and larger metaxylem area. These coordinated modifications demonstrated a comprehensive optimization throughout the root-leaf continuum. In contrast, under cold stress conditions, the positive effects of fungal inoculation were substantially diminished. Although a few traits, such as abaxial epidermal thickness and root cortical cell area, showed partial improvement, most anatomical parameters exhibited minimal responses to fungal treatments at low temperatures. This pronounced contrast between temperature regimes highlights the limited capacity of this single fungal strain to support anatomical adaptations under cold stress. These findings provide important insights into plant-microbe interactions under challenging environmental conditions and demonstrate that AMF-mediated benefits are strongly temperature dependent. Our work advances the understanding of the contextual nature of plant-AMF relationships and offers valuable anatomical perspectives for developing improved strategies to enhance plant resilience in cold-climate ecosystems.