By Robert Carter reporting for Native Plant News Summer 2025
You have seen fungus before, as mold on your cheese or mushrooms on your pizza. When you eat a mushroom, you are just eating the reproductive structure. Their life is much more complicated than the reproductive structure you see and eat. The majority of the mass of a fungus is tiny, threadlike, and rarely seen. It is underground or growing through wood, food, or sometimes your skin. These threadlike structures are called mycelia (mycelium is singular). Undetected by humans, the mycelium grows in search of food, water, minerals, and possibly a mate.
Some fungi are asexual, but many need to find a mycelium of the same species to reproduce. Whether sexually or asexually, they will produce spores. The mushrooms from the grocery store release spores from the riblike structures under the cap. Nonchalantly check it out the next time you are in the grocery store. If you are not nonchalant, you may get some strange looks.
It is challenging to find a mate while growing through the ground or some other substance. Fungal mycelia send out chemical signals called pheromones that help them detect similar and dissimilar fungi. When mycelia meet, they then need to negotiate a relationship that could be fusion for reproduction, tolerance, or hostility.
Mycelia benefit most plants, and vice versa
When mycelia encounter a plant root, a parasitic or mutualistic relationship can develop. If it is parasitic, the fungi often release chemicals that modify the plant growth to suit the fungus. The majority of plants are involved in fungal mutualisms in which both organisms benefit. Although mutualism may be considered mutual cooperation, it really is more like mutual exploitation. The plants provide the fungus with carbon (C) (sugar) while the mycelia provide the plant with water, phosphorus, nitrogen, and other minerals. Many plants have difficulty surviving without the assistance of mycorrhizae. Likewise, the mycorrhizal fungi rely on the plants for energy.
A plant will signal a need for a phosphorus (P) and the mycelium will deliver the P in exchange for sugar the plant makes through photosynthesis. The more P that is provided by the mycelia, the more sugar it will receive from the plant. Likewise, a plant root delivering lower levels of C will receive less P. It is almost like the fungus and the plant have negotiated a trade deal. The mycorrhizae even can redistribute minerals in the soil from areas of low concentration to high concentration.
The mycelia act somewhat like an extended root system; thus, they are often called mycorrhizae. The ”myco” means fungi while “rhizae” refers to roots. The area around the root is called the rhizosphere. There are two categories of mycorrhizae. Ectomycorrhiza forms a net around small root tips with some mycelia growing into the roots between cells. The mass of fungi growing around the roots is called a Hartig net. Endomycorrhiza, sometimes called arbuscular mycorrhizae (AM) surround some, but some of the mycelia grow into plant root cells.
A communication network for plants
The fungal connections between plants make communications possible. It is like the plants send each other emails. Sometimes plants can detect stressed plants and potentially send needed minerals. A wounded plant can release chemical signals that can cause responses in surrounding plants. This line of communication is something humans don’t yet fully understand.
Fungi can play some unexpected tricks. Many orchids are unable to germinate without fungi. The orchid seeds are tiny and have a small endosperm. Endosperm is the part of the seed that provides the energy for a seed to germinate. When you eat beans, you are primarily consuming endosperm. Mycorrhizae provides the minerals and sugar the orchid seed needs to germinate. If the fungus is not present in the soil, the seed will not successfully germinate. Truffles can trick animals. They send out a chemical signal that mimics pheromones that attract insects and mammals. The animals show up looking for a mate but are just being used to disburse fungal spores. Some fungi are able to attract and capture roundworms for food. Think about that. A fungus hunting an animal. I’m glad I am not on their menu.
We humans are quite proud of our ability to communicate over long distances. The telegraph began in the 1830’s, but fungi beat humans to this achievement by many thousands of years. When you enter a forest, prairie, or field of wildflowers, there is constant communication beneath your feet. I wonder if they can be gossiping about us.
References
Hathaway, M. and W. Arévaloarchive. April 24, 2023. How do fungi communicate? MIT Review. https://www.technologyreview.com/2023/04/24/1071363/fungi-fungus-communication-explainer/
Holewinski, Britt. Underground Networking: The Amazing Connections Beneath Your Feet. https://www.nationalforests.org/blog/underground-mycorrhizal-network
McCutcheon JP, and Lekberg Y. 2019. Symbiosis: Fungi as Shrewd Trade Negotiators. Current Biology 29: R570–R572. https://www.cell.com/current-biology/pdf/S0960-9822(19)30535-4.pdf
Robert Carter grew up exploring the Piedmont of South Carolina. He attended Clemson University (BS, MS) and Auburn University (PhD) to obtain degrees in forestry. His graduate research involved identifying landscape ecosystems using plants, soils, and landform in the mountains of North Carolina and the Longleaf Pine ecosystems of lower Alabama. After a career in academia, he moved back to South Carolina where he is a Forestry and Wildlife Agent for Clemson University Extension and Outdoor Education Specialist with the Catawba Indian Nation.