Abstract:

Aims Ectomycorrhiza (ECM) was generally considered to have a positive impact on the host plant exposed in contaminated soil and could enhance heavy metal tolerance. However, most researches have focused on single-ECM seedlings in experimental conditions, and the effects of mixed-ECM on the host are inadequately studied. Because woody plants are usually inoculated by mixed-ECM in natural conditions, it is essential to study the differences between single- and mixed-ECM inoculations, especially the dissimilar effects on heavy metal tolerance, which can help us better understand the mechanism of ectomycorrhiza.

Methods After a 4-week growth period, Pinus tabulaeformis seedlings inoculated by Boletus edulis and Xerocomus chrysenteron and the uninoculated control were planted in Cu and Cd contaminated soil. We measured growth and element accumulation 12 weeks later.

Important findings Compared with the uninoculated control, ECM inoculation not only enhanced the host's growth and biomass, but also reduced the concentration of heavy metals and their transportation from root to shoot. Seedlings inoculated by mixed-ECM strains had higher heavy metal tolerance than those inoculated by single-ECM strain. This advantage was especially remarkable at higher concentration. Results showed that in 3 mg·kg^-1 Cd contaminated soil, Cd concentrations in the shoot and root of mixed-ECM seedlings were only 59.1% and 70.7% of the control, 11.3% and 18.1% lower than single-ECM ones. However, the dry weights of mixed-ECM seedlings' shoot and root were 1.14 and 1.20 times than the control vs. 1.18 and 1.17 times for single-ECM. In 400 mg·kg^-1 Cu contaminated soil, the dry weights of mixed-ECM seedlings' shoot and root were 1.01 and 1.09 times than the control, while the Cu concentrations in the shoot and root of mixed-ECM seedlings were only 61.8% and 79.6% of the control, 0.7% and 3.8% lower than single-ECM seedlings.

Key words: ectomycorrhizal fungi, Pinus tabulaeformis, Cu, Cd, accumulation