Ectomycorrhizal fungi may not act as a barrier inhibiting host plant absorption of heavy metals while enhancing successful vegetation restoration on heavy-metal tailings

Yahua Chena,b,c, L. Shia, Y.Z. Tanga, B.H.Liua and Z.G. Shena,b,c

aCollege of Life Sciences, Nanjing Agricultural University, China

bJiangsu Collaborative Innovation Center for Solid Organic Waste Resource, Nanjing Agricultural University, China

cNational Joint Local Engineering Research Center for Rural Land Resources Use and Consolidation, Nanjing Agricultural University, Nanjing 210095, China

yahuachen@njau.edu.cn

Whether the huge external hyphal system of ectomycorrhizae that promotes host plants' acquisition ofwater and nutrients can selectively inhibit their transport of heavy metals at the same time remainsunclear.In the root-bag test, external hyphae took the initiative into the Cu/Cd-contaminated bulk soil, absorband transport Cu and Cd to the rhizosphere soils and further transport it to the shoots of the host plants.Inoculation with ectomycorrhizal fungi (EMF) also promoted the uptake of nutrients by host plants, thereby increasing theirbiomass and improving Cu/Cd tolerance compared with non-inoculated plants. Inoculation with EMFspecies with higher Cu or Cd tolerance generated more phytostabilization and phytoextraction of Cu orCd by host plants. Therefore, we concluded that EMF do not act asa barrier inhibiting the absorption of heavy metals by host plants, but rather promote this absorption. On the other hand, vegetation reconstruction on heavy-metal tailings dumps is a very difficult process. The survivorship of non-mycorrhizal (NM) seedlings after 6 months was only 56%. The survivorships of Laccarialaccata and Hebeloma vinosophyllum seedlings were 89% and 100%, respectively. Inoculation with EMF significantly promoted the absorption of nutrients, such as Pi, by host pine seedlings. Pine seedlings increased the numbers of soil bacterial communities and the activities of soil urease and acid phosphatase. H. vinosophyllum seedlings had the greatest effect among all of these soil indicator parameters. Mycorrhizal pine seedlings significantly reduced the availability of heavy metals in the soil and increased the amount of heavy metals transferred to host plant tissues. Cd-tolerant EMF were especially efficient promoters of these activities. Thus, the cultivation of ectomycorrhizal pine trees can improve soil quality in mining wastelands and increase the chances of successful vegetation restoration.

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