What Are Rhizomorphs and How Do They Affect Plants?

When you think of fungi, you might imagine mushrooms popping up in the forest floor. But there's more to fungi than meets the eye - and some of their most important structures are hidden underground.

The Basics: What Are Rhizomorphs?

Rhizomorphs are specialized structures that certain fungi use to grow through soil, wood, or other substrates. They're like tiny root systems, but instead of absorbing water and nutrients, they help the fungus spread and colonize new areas.

Rhizomorphs are made up of compacted hyphae, which are the thread-like structures that make up a fungus's body. Hyphae grow out from the main fungal body and explore their surroundings, releasing enzymes to break down organic matter and absorb nutrients.

As some hyphae grow and others die off, the fungus may start to form rhizomorphs as a more efficient way of spreading. Rhizomorphs can be several millimeters thick and extend for meters or even kilometers through substrate.

Why Do Fungi Form Rhizomorphs?

Rhizomorphs help fungi overcome some of the challenges of growing underground. For example:

• Competition with other organisms: In soil, fungi must compete with bacteria, other fungi, and plant roots for space and resources. By forming rhizomorphs, fungi can spread further and faster than they could by just growing outwards from a central location.
• Drought conditions: When soil dries out, hyphae can dry out and die. Rhizomorphs are more resistant to desiccation, so fungi that form rhizomorphs can survive in drier soils.
• Access to new resources: Rhizomorphs can grow through hard materials like wood or rock, breaking them down and accessing the nutrients inside. This allows fungi to exploit new ecological niches.

The Impacts of Rhizomorphs on Plants

While rhizomorphs can be beneficial to fungi, they can also have negative impacts on plants. Some ways that rhizomorph-forming fungi affect plants include:

• Root rot: Some fungi that form rhizomorphs can infect plant roots and cause root rot. The rhizomorphs help the fungus spread from one plant to another, making it difficult to control.
• Carbon cycling: When fungi form rhizomorphs in trees, they can break down the wood and release carbon back into the atmosphere. This has implications for global climate change.
• Ecosystem engineering: Some fungi that form rhizomorphs can alter the structure of soil and create more favorable conditions for their own growth. This can change the composition of plant communities over time.

Examples of Rhizomorph-Forming Fungi

Many types of fungi can form rhizomorphs, including some that are edible or used for medicinal purposes. Here are a few examples:

A chanterelle mushroom. Some species of chanterelle-forming fungi can produce rhizomorphs.

Oak wilt disease. The fungus that causes oak wilt can form rhizomorphs to spread between trees.

A medicinal reishi mushroom. Reishi-forming fungi can produce rhizomorphs as they grow through wood.

Rhizomorphs are fascinating structures that allow fungi to spread and thrive in challenging environments. However, they can also have negative impacts on plants and ecosystems. By understanding the role of rhizomorphs in fungal ecology, we can better manage the interactions between fungi and other organisms in our environment.

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