Metal soil contamination, metallophytes and arbuscular mycorrhizal fungi from South America

BECERRA, ALEJANDRA G.; MENOYO, EUGENIA; CORNEJO PABLO; CABELLO M

Mycorrhizal Fungi in South America: Biodiversity, Conservation, and Sustainable Food Production

SPRINGER

Año: 2022; p. 219 - 236

Soils are the most valuable ecosystem in the world (Pepper et al. 2009) because they provide ecosystem services needed for life on the earth (FAO and ITPS 2015). However, soil, water, and air pollution represent severe environmental problems that can affect quality and human health (FAO and UNEP 2021).Soil contamination has frequently been used as a synonym for soil pollution. Soil pollution is defined as the presence of a chemical or substance (heavy metals, pesticides, etc.) out of place with a higher than normal concentration with adverse effects on nontargeted organisms (FAO and ITPS 2015). Human activities release pollutants to the environment (Swartjes 2011) affecting various species and ecosystems on the planet.Heavy metals (HM) are a group of metals and metalloids with a relatively high atomic mass (>4.5 g/cm3) such as Pb, Cd, Cu, Hg, Sn, and Zn that cause toxicity problems. These elements naturally occur at low concentrations in soils, and many are essential for plants, animals, and humans. High HM concentrations may cause phytotoxicity, which accumulate in tissues and living organisms. The main anthropogenic sources of HM are industrial areas, mine tailings, disposal of metal wastes, leaded gasoline and paints, fertilizers, pesticides, coal combustion residues, etc. (Alloway 2013). Among the HM, Zn, Ni, Co, and Cu are more toxic to plants; meanwhile, As, Cd, Pb, Cr, and Hg are more toxic to higher animals (McBride 1994).Remediating polluted soils requires advanced technologies. Researchers and remediation companies are investing in technologies that enable environmentally and sustainable remediation (Duarte et al. 2018). A promising biological method proposed for cleanup of contaminated environments is phytoremediation (Sessitsch et al. 2013; Thijs et al. 2017). Phytoremediation uses plants and their associated microorganisms to remove, reduce, transform, mineralize, degrade, volatilize, or stabilize contaminants through their metabolic activities (Kelley et al. 2000; Miretzky et al. 2004; Cherian and Oliveira 2006; Cho et al. 2008). Depending on the type of pollutant, different strategies for phytoremediation are recognized: phytoextraction, phytodegradation, rhizofiltration phytostabilization, and phytovolatilization (Ashraf et al. 2019). Briefly, (1) phytoextraction is the uptake of HM by the harvestable parts of plant, (2) phytodegradation is the decomposition of pollutants by plants and microbes, (3) rhizofiltration is the absorption of metals from polluted waters, (4) phytostabilization produces a decreased mobility and immobilization of pollutants in soil by plant roots and microbes, and (5) phytovolatilization is the volatilization of pollutant into the atmosphere by plant roots (Chaudhry et al. 1998; Khan et al. 2000). A wide diversity of plant species has been identified, due to their great capacity to accumulate HM, which are called metal hyperaccumulating plants.In phytoremediation, soil microorganisms must include the mycorrhizal fungi in soil restoration programs (Haselwandter and Bowen 1996). Arbuscular mycorrhizal (AM) associations enhance soil phytoremediation processes since they improve plant growth-promoting, pollutant-degrading, and/or detoxification capacities (Chen et al. 2018; Begum et al. 2019). Arbuscular mycorrhizal fungi (AMF) are ubiquitous in soil being present on the roots of plants growing on HM-contaminated soils playing an important role in metal accumulation and tolerance (Gaur and Adholeya 2004; Khade and Adholeya 2009; Miransari 2011). When polluted soil is treated with AM-colonized plants, an important point to be considered is the selection of appropriate AMF species since they are most efficient and have the ability to survive under metal stress conditions being more efficient that other AMF species (Miransari 2011; Meier et al. 2012b).The objective of this chapter is to show a list of metallophyte/hyperaccumulator plant species registered for South America with their mycorrhizal status. Specifically, we focused on the relationship between AMF symbiosis with metallophytes in soils contaminated with Cu from Chile and soils contaminated with Pb from Central of Argentina.