Heavy metal binding by mycorrhizal fungi

Abstract

Ecto‐ and endomycorrhizal symbiosis can play a crucial role in protecting plant roots from heavy metals (HMs). The efficiency of protection, however, differs between distinct isolates of mycorrhizal fungi and different HMs. Fungal ecotypes from HM‐contaminated sites seem to be more tolerant to HMs than reference strains from non‐contaminated sites. The abundance of the extramatrical mycelium was shown to he important for HM binding by the fungus. Most of the HMs were demonstrated to be bound to cell wall components like chitin, cellulose. cellulose derivatives and mela‐nins. The chemical nature of HM‐binding substances in the fungal cells is not clear. Polyphosphate granules, which were proposed to have this function, seem to be artifacts of specimen preparation. The high N and S concentrations associated with the polyphosphate granules rather indicate the occurrence of HM‐thiolate hinding by metallothionein‐like peptides.

Uptake of cadmium from an experimentally contaminated calcareous soil by arbuscular mycorrhizal maize ( Zea mays L.)

“…Alleviation of heavy metal phytotoxicity by arbuscular mycorrhiza has been indicated in several studies (Schüepp et al 1987;Heggo et al 1990;Zhu et al 2001;Chen et al 2003). The AM fungi may act indirectly, for example by enhancing plant P nutrition and increasing plant growth with a resulting dilution effect of the metal in the host plant, or directly by binding of the metal to the fungal mycelium and immobilization in the rhizosphere or the roots (Galli et al 1994;Joner et al 2000;Chen et al 2001). Nonmycorrhizal metal hyperaccumulators may thus be suitable for phytoremediation of contaminated sites while mycorrhizal colonizers may be more useful for phytostabilization of heavy metals in the field.…”

Mycorrhizal Fungi Increase Chromium Uptake by Sunflower Plants: Influence on Tissue Mineral Concentration, Growth, and Gas Exchange

“…[4] Mycorrhizal fungi have greatest impact on elements with narrow diffusion zones around plant roots, including heavy metals and phosporus (P). [5,6] Mycorrhiza enhance the uptake of Cu, [7] Zn, [5,8,9] nickel (Ni), [10] Cd, [11,12] Pb, [13] and other metals. [9] Mycorrhiza increase nutrient and water uptake, alleviate cultural and environmental stresses, and enhance disease resistance and plant health.…”

“…[5,6] Mycorrhiza enhance the uptake of Cu, [7] Zn, [5,8,9] nickel (Ni), [10] Cd, [11,12] Pb, [13] and other metals. [9] Mycorrhiza increase nutrient and water uptake, alleviate cultural and environmental stresses, and enhance disease resistance and plant health. [14][15][16][17][18][19] An important arbuscular mycorrhizal genus is Glomus, which colonize a variety of host species, [6] including sunflower.…”

Fungos micorrízicos arbusculares em solos de área poluída com metais pesados

“…Esses resultados evidenciam que os FMAs podem adquirir tolerância aos metais pesados, dependendo do grau de poluição do solo e da ocorrência de plantas hospedeiras (Galli et al, 1993), visto que tais fungos são biotróficos obrigatórios na natureza.…”