The Exciting world of Mycorrhizal fungi!

Over 500 million years plants have been evolving alongside other organisms and interacting with them.

In recent years, a form of mutualistic symbiosis has been attracting much attention to the lithosphere surrounding plant roots. This mutualism is between mycorrhizal fungi and plants. The word Mycorrhizae signifies the relationship and role the fungi (Myco) have around plant root systems (Rhizosphere), whereby the fungi can increase the plants access to nutrients and water by creating an additional root system of mycelial growth and making inaccessible nutrients accessible. In doing this, the plant then provides sugar and carbon to the fungi, creating a mutualistic relationship.

Most mycorrhizae fungi can be divided in to two groups, Arbuscular mycorrhiza and Ectomycorrhiza. Arbuscular mycorrhiza will penetrate the plant root tissue using hyphae to tap into the plant directly, whilst Ectomycorrhiza covers the roots in a sheath of mycelium which interacts with the root’s outer cells. By creating this connection, the fungi is able to deliver the nutrients whilst simultaneously feeding.

Nitrogen and Phosphorus are two important macro nutrients associated with plant root growth and vegetative growth. Both can become inaccessible in the soil around roots. Mycorrhizal fungi can branch out further, making these and other nutrients available. Mycorrhizal fungi can also increase drought tolerance in plants, by branching out and increasing the absorption area by up to fifty times. Delivering water which would otherwise be inaccessible in the soil.

However, if these nutrients are already in abundance within the soil and easily accessible to the plant, the Mycorrhizal fungi is unlikely to create a symbiotic colony. It is therefore important to use minimal fertilisers when trying to harness the full benefit of Mycorrhizal fungi mutualistic symbiosis. Some suggest reducing Nitrogen and Phosphorus by over 50% when using fertilisers in conjunction with Mycorrhizal fungi.

The brilliance of this underground connection doesn’t stop there though. Scientists began to realise that these fungi are also connecting to multiple plants simultaneously, creating a network between different organisms. This network allows plants to share nutrients between themselves, and even communicate! When a plant connected to the network is stressed by a pathogen or pest it releases chemicals which are then transferred along the mycelial strands to other plants in the network. These plants can then use defensive measures before coming under attack. This network of Mycorrhizal fungi, alongside other microorganisms within the soil underneath forest floors is now being regarded as The World Wood Web.

Image: Mycorrhizal networks: how trees talk through the wood-wide web | BBC Science Focus Magazine

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