Adaptation Mechanisms of Polytrichales to Abiotic Stress: A Review

Abstract

Polytrichales are ecologically important mosses that inhabit diverse terrestrial environments and frequently experience dehydration, oxidative stress, temperature fluctuations, and high light intensity. Their ability to withstand substantial water loss and rapidly recover after rehydration makes them valuable models for understanding plant stress tolerance. This review aims to synthesize current knowledge of the structural, physiological, biochemical, and molecular mechanisms underlying abiotic-stress tolerance in Polytrichales, with particular emphasis on desiccation tolerance, and to identify key research gaps and future directions. Specialized leaf structures and lamellae help regulate water balance, while metabolic adjustments and preservation of photosynthetic machinery support cellular survival during dehydration. Antioxidant enzymes, including superoxide dismutase, catalase, and peroxidases, regulate reactive oxygen species and limit oxidative damage. The accumulation of soluble sugars, compatible solutes, protective proteins, and other metabolites further stabilizes membranes and cellular macromolecules. Upon rehydration, photoprotective, repair, and stress-signaling mechanisms promote rapid recovery of photosynthesis and cellular function. Studies of Polytrichum formosum indicate that chloroplasts and mitochondria can remain relatively well-preserved during dehydration, facilitating recovery. However, species-specific information remains limited, particularly regarding responses to combined and fluctuating stresses. Future research integrating physiological, transcriptomic, proteomic, metabolomic, and ultrastructural approaches will help clarify the mechanisms and ecological significance of stress tolerance in Polytrichales. Overall, Polytrichales provide valuable models for understanding plant resilience, desiccation tolerance, and adaptation to increasingly variable environments.