19 August 2022

Mycelium: Exploring the hidden dimension

Discover the incredible networks of fungi living right beneath our feet.

By Eddie Johnston

A family walk through a blue woven tunnel structure in a glade

When you think of fungi, the first image that pops into your head is probably a mushroom.

But there’s so much more to fungi, and it’s hidden beneath our feet.

Under the fruiting bodies we know as mushrooms, lies a hidden part of the fungus: the mycelium.

Inspired by Malgorzata Lisiecka’s ‘Hidden Dimension’ artwork that's part of Nourish at Wakehurst this summer, we’re unearthing the secrets of this underground network.

Immersive willow and textile sculptures, which mirror the thread-like networks of fungi beneath our feet.
Hidden Dimension installation at Nourish, Jim Holden © RBG Kew

Putting down ‘roots’

You might have seen mycelium before as a fuzzy, white, green or even black mass growing on mouldy food.

But out in the wild, mycelium is more than just the sign of an out-of-date sandwich: it’s a whole network of thin strands called hyphae.

The mycelium has a similar function in fungi to the roots of plants. They secrete digestive enzymes onto their food source, often dead organic materials, to break them down into smaller parts.

The hyphae can then absorb these smaller parts to feed the fungus as a whole.

Green and brown stripes with blue threads growing around them
Micrograph image of Epichloë scottii hyphae (in blue) on the surface of a stem of wood melick (Melica uniflora), Yvonne Becker, Julius Kühn Institute – Federal Research Centre for Cultivated Plants, Braunschweig, Germany CC BY SA 4.0
A red mass of growing tendrils
Fungal hyphae stained with dye, Ajay Kumar Chaurasiya on Wikimedia Commons CC BY SA 4.0

In fact, this process of breaking down organic matter is critical in maintaining healthy soil, providing food for the vast array of bacteria and animals that call soil home.

Mycelial networks can be both large and small. Some are almost microscopic, only affecting tiny areas around them.

But they can grow to colossal sizes as well. In the United States, an Armillaria ostoyae growing under the Malhuer Nation Forest in Oregon is estimated to have an area of almost 10 square kilometres, making it one of the largest single organisms in the world!

A brown cluster of mushrooms growing in a green forest dell
Armillaria ostoyae growing in southern Germany, Holger Krisp on Wikimedia Commons CC BY SA 3.0

Making the connection

The mycelium also plays a crucial role in fungal reproduction.

Many fungi reproduce using spores — these are tiny, seed-like structures that are carried away from the fruiting body of a fungi by the wind or by animals.

When they land on the ground, they begin growing into a new mycelium.

Fungi can also split their mycelium off into smaller fragments, which then go on to form independent mycelium networks.

A semi-transparent image of a spore
A spore from a Laccaria fungus, © Natalia Vargas

But some fungi can reproduce in another way, and the mycelium plays a crucial role in it.

It’s possible for the mycelium network of two compatible fungi to fuse together, allowing the cells of each fungi to combine and their DNA to mix.

It’s essentially how fungi have sex (although not all of them have it, and those that do, only do when the environmental conditions are just right).

After fusing, the cells then eventually end up in new spores held inside the fungal body (like truffles) or exposed to the outside world (such as toadstools), which can spread the fungi far and wide.

Countless white threads growing organically on a black background
Mycelium, made up of hyphae, Rob Hille on Wikimedia Commons CC BY SA 3.0

The Wood Wide Web

But it’s not just other hyphae that fungi create networks with.

Mycelium can actually fuse with the root systems of plants and trees, creating a cross-kingdom web known as the mycorrhizal (meaning 'fungus root') network.

This network benefits everyone involved. Through photosynthesis, trees and other plants produce sugars, vitamins and in some cases fats, which via their roots, the fungi can absorb. In turn, the fungi help the trees and plants absorb water and minerals from the soil, beyond the reach of their roots and root hairs.

Playing matchmaker

Some plants actually require very specific fungi to sprout, and as a result, have been heavily effected by land use and climate change. The Lady Slipper orchid is now so rare in the UK, that just one plant remains in the wild and it’s protected in a top-secret location. But Kew is working to save the species, by identifying which specific species of fungus is its perfect match.

Discover more

In fact, there is a small group of plant species that relies exclusively on mycelium networks for energy, as they are unable to generate their own sugars and vitamins from photosynthesis due to a lack of chlorophyll. 

Plants also use the mycorrhizal networks as a way of sharing messages with their plant neighbours.

It’s been known for some time that plants use chemical messages to ‘communicate’ with each other, sending warnings of predators and even toxic hormones that can slow down the growth of other plants.

But recent scientific studies found that mycorrhizal networks can help these messages travel further, helping plants to remain connected over longer distances, so long as they have the same fungi connected to their roots.

Mycorrhizal fungi also work in symbiosis with plant roots to play a crucial role in removing carbon from the atmosphere. As part of our Nature Unlocked research project, Kew Scientists are measuring fungal diversity and carbon storage below ground, with aim to scale it up to habitats UK-wide.

It was even found that tomato plants infected with the disease early blight (Alternaria solani) would send signals to their healthy neighbours, who in response produce defensive enzymes to help protect against potential infection.

Dark grey blotches growing on green leaves
Early blight (Alternaria solani) growing on potato leaves, Linnea Stridh on Wikimedia Commons CC BY-SA 4.0

So the next time you go for a walk in a woodland, a garden or even a park, as peaceful as it may be, remember that underground, out of sight, the fungi are always chatting!

A colourful illustration of food crops

Nourish

Join us this summer for Nourish at Wakehurst, Kew’s wild botanic garden in Sussex, and embark on a journey through spectacular, immersive artworks inspired by Kew’s world-leading international science projects.

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