The current view on heavy metal remediation: The relevance of the plant interaction with arbuscular mycorrhizal fungi

In the last years, heavy metal (HM) pollution has spread across natural and anthropic ecosystems posing inevitable, serious health risks. Commitments to resolve this issue resulted in tightening regulations and calls to action. The use of plants and their symbionts for remediation enjoys support. Nonetheless, keystones between mycorrhizal research and their application have still to be identified. The aim of this work was to provide an updated outlook on the current HM remediation contexts, with particular focus on the relevance of arbuscular mycorrhizal (AM) symbiosis as part of the plant-soil system. The AM potential implication in enhancing plant survival and performance in presence of HM stress could translate into efficient mitigation of environmental and health risks associated with increasing contamination of natural and human-managed ecosystems. Dust lift-up and leaching of HMs are the main routes of exposure and spread of pollution. The plant-soil system can reduce these risks. Moreover, the plants growing on HM-contaminated lands display decreased chlorophyll level as common toxicity symptom. Therefore, changes occurring in the chlorophyll content and/or in chlorophyllassociated parameters can be used as indicators revealing plant survival and physiological performance in phytoremediation contexts. Available scientific information suggests that plant inoculation with arbuscular mycorrhizal fungi (AMF) increases chlorophyll levels in most cases. Such response most likely occurs as the burden of HM stress is sustained by the symbiotic partners together, so that each partner has a role in mitigating the HM negative effects. Contaminated agricultural land and urban land come with their particular challenges. Feasibility in decontaminating them strictly relies on the achievement of long-term desired outcomes. Hence, perennial energy crops that establish successful AM symbiosis represent the best candidate plant species for further research on phytoremediation approaches.