Effects of arbuscular mycorrhizal inoculation on metallophyte and agricultural plants growing at increasing copper levels

A pot culture experiment was carried out to assay the behavior of different arbuscular mycorrhizal (AM) fungal inocula on plant growth and copper (Cu) uptake using two metallophytes (Oenothera picensis and Imperata condensata) and one agricultural plant (Helianthus annuus) grown at increasing Cu supply levels. Plants were established in a Cu polluted soil spiked with 0, 150, 300 or 450mg Cukg ^-1, and inoculated or not with: (i) Cu-adapted AM fungi (GA) or (ii) the Cu non-adapted strain Glomus claroideum (GC). Differences in plant biomass between inoculated and uninoculated plants were found, which were dependent on the AM fungal inocula used and the Cu level applied. Although the beneficial effect of AM fungi in promoting plant biomass production was not observed in metallophytes plants, a positive interaction between GA and H. annuus increased the shoot growth, especially at higher Cu levels. In addition, the Cu transfer from the roots to the shoots was low, remaining mostly at root level, especially in non-mycorrhizal plants; however AM fungi produced changes in Cu distribution increasing the translocation to the shoots. Differences in AM fungal parameters (root colonization, spore number and glomalin production) were strictly dependent on the Cu level and the AM fungal inoculum, suggesting the existence of certain compatibility, which was dependent on the particular combination AM-plant used. Specifically, the glomalin accumulation and Cu-bound to glomalin were significantly higher in AM colonized H. annuus plants, which could suggest a highly efficient way to reduce the Cu toxicity levels in soil. Therefore the use of H. annuus with AM fungal could promote phytostabilization processes.