Mycorrhizae Adsorb and Bioaccumulate Heavy and Radioactive Metals

Abstract

Mycorrhizae are mutual symbiosis (associations) between plant roots and a wide group of soil-inhabiting, filamentous fungi. Both partners exchange essential nutrients required for their growth and survival. The fungal partner acquires nitrogen, phosphorus, and other nutrients from the soil environment and exchanges them with the plant partner for photosynthetically derived carbon compounds that are essential for its metabolism. Primary function of mycorrhizal fungi is nutrient exchange. In light of growing urbanization, industrialization, and greater environmental disturbances, much effort is being directed toward friendly interaction of man and the environment. As such, considering the new technological and biotechnological advances in the field of ecology and environmental studies, from a management perspective, the genetic potential to mediate virtually any biogeochemical reaction and the habitat needed to support it exist in most soils which with developing specialized capabilities could be investigated further. When mycorrhizae are present in the soil, even under suboptimal conditions, the rhizosphere is more metabolically active. Fungal metabolic activities produce organic acids that percolate with rainwater down through the soil profile and contribute to accelerated weathering of mineral of the soil, and this provides an opportunity for mycorrhizal propagules to adsorb and/or to interact with metal ions under proper matrix potential of the soil. Recent studies have shown that ecosystems are constantly contaminated through wet and dry deposition of atmospheric pollutants such as gases, heavy metals, and radioactive isotopes. Mycorrrhizal fungi have been used as biotracers, bioaccumulators, and biodegraders of toxic compounds. For example, adsorption of radioactive isotopes and heavy metals has been demonstrated in Caspian (Hyrcanian) deciduous forests of Iran. Spore surface and ornamentation contributed to metal adsorption capability of AM fungal spores, with larger and highly ornamented spores demonstrating the highest adsorption readings of many cations. However, adsorbing range of heavy and radioactive metals may be species specific and within a certain range of tolerance.