The Fungi

© Hartmann Linge, 

Wikimedia Commons

What comes to mind when you think about fungi? Perhaps it’s mold on a bread slice, a bright red mushroom on the forest floor, or maybe you’re not sure what a fungus is. Regardless, fungi are so much more. Not only are the visible portions of a fungus usually just a small part of a larger organism, but many fungi are difficult to see because they’re under the soil, inside a tree, or microscopic. The truth is fungi are everywhere. 

A fairy ring. The mushrooms mark the outer reaches
of the entire underground fungal growth.

Mushrooms may be easily visible, but they’re only part of a larger system. A mushroom is simply the fruiting body of the larger, unseen mycelial mat. (A mycelial mat is the portion of a fungus not usually seen by human eyes. It’s responsible for uptake of nutrients and water and for most other functions as well.) Mushrooms are responsible for releasing spores into the air. The spores then travel on air currents in the hopes that they land somewhere with the right conditions to allow for growth of a new fungus. While a single mushroom cannot show the true size of the underground mycelium, a group of them might be able to. This is seen in fairy rings where the mushroom ring outlines the entire area of growth.

Walking through a forest you often see fallen trees and other debris rotting on the floor. What causes that debris to rot? Fungi. And it’s a good thing too. If that material didn’t rot and break down the forest floor would slowly accumulate more and more stuff. Eventually the floor would be so full that nothing could grow up through the choking mass of debris. The only things that would survive would be the trees already present, but even they would eventually die. At some point all the trees would die and nothing would be left except a pile of dead logs and accumulated leaf litter.

© Mary and Angus Hogg, Wikimedia Commons

Decomposition (the same thing as rotting just a more technical term) is important for two main reasons. One, as mentioned above, it helps break down debris and keep the ground clear. Two, by breaking down the debris it returns the nutrients in forms that can be reused by other plants. Without this cycling of nutrients plants wouldn’t be able to grow and thrive regardless of the availability of space on the forest floor. Fungi’s roll in decomposition makes it one of the most important players in the plant cycle. Without fungi the cycle would stop.

While decomposition of fallen trees and debris is generally good for still living and future plants, rotting of living tissue is not. Some fungi will infect a tree and start breaking down the inner part of the tree. The tree may look perfectly healthy and then one day fall over. And it won’t be until it’s fallen over on the ground that you can tell it had been rotted from the inside out.

Fungi can also help plants grow and thrive in environments that might normally be inhospitable to a plant. Fungi do this through a mycorrhizal association with the roots of a plant. This association is symbiotic between the plant and the fungus. (Symbiotic relationships are when two or more species form a close working relationship, often for long periods of time. These relationships can take different forms: benefit all; benefit one and hurt another (parasites); and benefit one without hurting the other.) The fungus is able to pull water and nutrients out of the soil that the plant may not be able to get at for a variety of reasons: soil pH, water content, etc. The fungus then transports these to the plant’s roots where the plant exchanges the nutrients for carbohydrates.

A elm tree showing the 

effects of Dutch elm disease.

© Luis Fernández García,

Wikimedia Commons

Not all fungi are helpful though. It’s estimated that more than 80% of all plant diseases are caused by fungi. These diseases cover a broad spectrum of symptoms and effects. Some fungi simply infect a few leaves and don’t hurt the overall health of the plant, but others can start on a leaf and quickly make its way through the whole plant. Destroying the plant host as it goes.

Most plants and fungi in an area have evolved together over time. The fungi come up with a new way to infect, and the tree responds with a new defense. In general this keeps them fairly well matched. Fungi still infect certain specimens, but most are able to fight off the infections. The issue arises with introduced pathogens. Fungi from other continents might present challenges to native species. Diseases like Dutch elm disease and sycamore anthracnose are the result of fungi that were introduced into areas with plant species that had no defenses to them. This has led to the death and disfigurement of large numbers of both elm and sycamore trees.

Next time you’re out walking around I hope this blog helps you understand the role of fungi in your life. Remember that many things in life wouldn’t be possible without them. They help the plants grow and through them help us as well. And while fungi do cause many problems, their positives far outweigh their negatives. And last, but definitely not least, without fungi in the form of yeast we would have neither bread nor beer. Mull about that next time you’re sitting in a brewery/bakery enjoying the fruits of a fungi’s labor.

As always tune in next week for another informative article.

Josh