Mycorrhizal fungi

The soil is packed with fungi fulfilling a range of functions in the soil but one group, mycorrhizal fungi are especially important.

Fungi perform a number of roles in the soil. They degrade organic matter, bind soil particles, can be plant pathogens and are a food source for some fauna. However, one group of fungi perform another role – they provide plants with nutrients.

Mycorrhizal fungi form mutualistic relationships with plant roots, that is a relationship where both partners benefit. The name mycorrhiza comes from the Greek mykes meaning fungus and rhiza meaning root. They are incredibly common, approximately 95 % of plant species have mycorrhizal fungi.

A mutualistic relationship

A mutualistic relationship is one in which both partners benefit. For plants, the main benefit is access to nutrients.

Mycorrhizae are much finer than plant roots so are able to penetrate into the soil. In a single gram of soil you might get up to 20 m of fungal hyphae.

This means they can exploit that gram of soil to a much greater extent than a single large root. Mycorrhizae can also gain access to nutrients that plants can’t get to on their own. One of the ways they do this is to access soil phosphorus the plant can’t get to.

Phosphorus is an important nutrient for plant growth. Mycorrhizae can produce enzymes and other substances which contribute to the breakdown of soils providing the plant with a lot better access to phosphorus. Some mycorrhizae can also produce enzymes that help to convert nitrogen in organic matter into forms that the plant can take up providing much quicker access to nutrients.

For mycorrhizae the main benefits are access to carbon. Plants are able to produce carbon directly through the process of photosynthesis (the process by which green plants use sunlight to synthesize sugars from carbon dioxide and water) which mycorrhizal fungi are not able to do. Between 10 and 30% of the sugars produced by photosynthesis go to the mycorrhizal fungi.

Types of mycorrhizal fungi

There are three main types of mycorrhizal fungi:

• arbuscular mycorrhizae
• ectomycorrhizae
• ericoid mycorrhizae

These different types all have different ways of linking to plants and partner with different species.

If this is something that you are interested in you can learn about the different mycorrhizal types