User:Tjx2/Ectomycorrhizal extramatrical mycelium

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The presence of long-distance extramatrical hyphae may affect forest health via the formation of common mycelial networks, in which hyphal connections form between plant hosts, located between the root cells of the host, and can facilitate the transfer of carbon and nutrients between hosts. While common mycelial networks (CMNs) allow for interplant carbon exchange primarily between photosynthetic plants, a number of non-photosynthetic plants have also adapted to participate in carbon transfer via CMNs. The extensive reach of the network beyond the roots of a plant enables the fungal hyphae to provide mineral nutrients to its host plant in exchange for carbon.[26]

Beyond facilitating nutrient transfer, CMNs have several other functions including compound signaling and plant-plant communication.[35] CMNs transfer warning signs of pathogen attacks between plants and allow newly developed roots to quickly become colonized by a fully functioning fungal mycelium.[36] CMNs connect many plants and stress-induced signals are transferred from the stress-inflicted plant to others, activating defense-related responses. These warning signals originate from the plant itself and proceed to the roots of the plant. From the roots, the signals enter the mycorrhizal fungi and travel through the network to relay warnings to other plants connected to the network. Mycelial networks may also be responsible for facilitating the transport of allelopathic chemicals from the supplying plant directly to the rhizosphere of other plants. Ectomycorrhizal fungi increase primary production in host plants, with multi trophic effects. In this way, extramatrical mycelium is important to the maintenance of soil food webs, supplying a significant nutritive source to invertebrates and microorganisms as well as overall plant competition and diversity.

While CMNs enable mutually beneficial connections between plants via nutrient transfer and defense warnings, these networks can also lead to unequal relationships between plants in which one benefits at the expense of the other. In a CMN shared between two plants, it is possible that one plant receives more nutrients from the network or supplies an unequal amount of carbon to mutual fungal hyphae, resulting in that plant species exploiting the network and gaining more than the other. Consequently, the other plant will be worse off due to the CMN connecting it to the exploitative plant.[26]

There are two types of mycorrhizal networks. Most plants are associated with arbuscular mycorrhizal fungi (AMF). AMF are able to form symbioses with several plant species and connect to roots of different hosts, allowing CMN. Mycelium networks function through signals that are first produced in plants, then move to the roots and then migrate to AMF. Then, signals go through the plant surface where they can be transported to leaves or other organs. Cells respond to these signals by forming a tube-like structure in preparation for the fungal hyphae.[37] Mycelia of AMF can link many plants across large areas.

The second type is ectomycorrhizal networks (ECMs). ECM fungi are extremely diverse, resulting in varied behaviors towards their plant hosts. Compared to AMFs, ECM are more diverse and form mainly in trees. ECMs mediate plant and tree nutrients by interrupting the sylvigenetic cycle during maturity. Because ECMs vary by tree, tree cutting and logging has shown a reduction in the ECM fungal community. Thus, creating imitations of ECMs in artificial ecosystems could be a solution for designing urban green spaces.[38]