Bryophyte tolerance to potentially toxic elements: implications for environmental monitoring and remediation

Pollution caused by potentially toxic elements (PTEs) is a serious global threat to the environment. In this context, sensitive and suitable tools for environmental assessment are necessary. As early diverging land plants with simple morphology and direct exposure to the atmosphere, bryophytes have emerged as powerful bioindicators and biomonitors of PTEs stress. This review focuses on current knowledge available regarding ecological relevance, sensitivity, physiological and molecular mechanistic basis underlying bryophytes in response to PTEs stress. Earlier studies indicate that bryophytes possess effective mechanism to tolerate PTEs, including metal uptake regulation, cell wall binding, vacuolar compartmentalization, antioxidant defence, phytochelatin synthesis, and metabolic reprogramming. The effects of PTEs on bryophyte growth, development, photosynthesis, oxidative balance, and nitrogen metabolism have been critically evaluated and it was identified that responses vary greatly between species and with different metals. Recent advances in ultrastructural, molecular and metabolomic approaches further highlight the value of bryophytes as model systems for understanding both conserved and lineage-specific stress-tolerance mechanisms in land plants.