Science Saturday - Mycorrhiza: A Fungus Among Us

Welcome to Science Saturday! There is a huge amount of science that goes into what we do and we want you to know about it. This is the third post in our series. In future posts we'll discuss topics like soil health, organic certifications, how your body uses the plant nutrients you eat, and more so stay tuned!

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Avalow Science Saturday

Let’s dive right into one of the most important components of plant growth: mycorrhiza. The word itself is a bit of a mouthful; it’s pronounced “mike-ah-rice-ah”. Go ahead, give it a try…mike-ah-rice-ah. Good!

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Simply put, mycorrhiza are fungi that have a symbiotic relationship (they work as a team) with plant roots to scavenge for moisture and nutrients. “Mykos” is the Greek word for fungus and “rhiza” for root. The name literally means “fungus root”. Funny name, but mycorrhiza are serious business as they make survival of most of the world’s plants possible and likely allowed early land plants to quickly take over large swaths of the Earth’s surface about 450 million years ago.

Today, 90% of plants live in tandem with mycorrhizal fungi. And, please remember, these two organisms come from totally different “kingdoms,” the highest level we use to differentiate the various living things on our Planet Earth. Plants and fungi are as distinct as animals and fungi! These fungi live inside plant roots (endomycorrhizal) or on the surface of plant roots (ectomycorrhizal), their tissues connected to allow fluids and nutrients to flow from one to another. Let’s just say it’s a very close relationship.

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But what is the purpose of these two very different organisms living together? It comes down to a “you scratch my back, I’ll scratch yours” partnership. Plants are really efficient at producing carbohydrates (see: photosynthesis) but not particularly good at scavenging for critical growth nutrients like phosphorus and nitrogen. Mycorrhiza fill that need for plants. They are heterotrophic, meaning they get their nutrients from their environment. Their fungal structure easily absorbs nutrients, most notably nitrogen and phosphorus. These are absorbed and passed to the host plant in exchange for carbohydrates. The fungal structure (hyphae) has massive surface area, giving the host plant a much larger effective root system than it would have without the fungus partner.

Pretty cool stuff, I think. But there’s one catch: non-mycorrhizal plants. Yes, there are plants that have evolved a “resistance” to being colonized by fungal friends. The reason is a bit beyond the scope of this article. Suffice it to say that one of the family of resistant plants is the Brassicaceae family, including cabbage, cauliflower, and broccoli. Nature sure has many twists and turns!

At Avalow, the custom garden soil mix is formulated from a number of components and is devoid of mycorrhizal fungus. The mix is high in nutrients needed by plants for growth, flowering, and fruit set and we focus on ensuring the overall microbial health is balanced. Combined with easy access to water via their sub-irrigation system, the environment is ideal for plants to uptake nutrients and water without requiring fungal partners.

I hope this installment of Science Saturday has helped you envision the micro-activities going on in your garden. Important garden science is often too small to see with the naked eye or hidden below the soil surface, away from the heat, sun, and cold. This is certainly the case with the symbiotic work of plants and mycorrhizal fungi.