Mycorrhizal Relationships

Though mycorrhizae are incredibly common (and functionally important) to land plants, they are in rapid decline. We are farming in ways that destroy these fungal interactions, and we are now farming on half of the world’s land.

Read on below about plant mycorrhizal relationships and why they are important in organic farming systems:

A hand holds plant roots pulled from the ground. They have small white nodes on them. The roots store nitrogen in the ground and have a relationship with the fungi in the soil to access nutrients..

“Our hands imbibe like roots, so I place them on what is beautiful in this world.” – Francis of Assisi

Dear Friend,

The interactions between plant roots and fungi (aka mycorrhizae relationships) are quite intimate.

As the mycologist Merlin Sheldrake puts it: It’s not sex (there’s no genetic exchange), nonetheless, the intimacy of the partnership is sexy!

Changes to both the root cells and the fungus begin to occur before they even touch:

Root exudates lure compatible fungal threads while simultaneously deterring others that are not well matched.
The fungal threads have a special organ, the spitzenkorper, that guides the tip toward the chemical stimulus from the roots.

The mechanisms underlying plant/mycorrhizal compatibility are not well understood and while some fungi are quite picky about the identity of their host plant, many are promiscuous. If given the opportunity, individual mycorrhizae will form partnerships with many different plants at any given time.

Scientific literature is full of alluring words describing what comes next. Entanglement, stimulus, penetration, intracellular exchange. The fungus ultimately forms an arbuscule (a tree-like structure) inside the plant root cells, specifically for the exchange of fluids.

Do I have your attention yet? Good, because the relationship is important.

An image of microscopic fungal cells with the hyphae of plant roots interacting with the cells

Source: https://mycorrhizas.info/vam.html

Impacts of Farming on Fungi Symbioses

Though mycorrhizae are incredibly common (and functionally important) to land plants, they are in rapid decline.

We are farming in ways that destroy these interactions…

…and we are now farming on half of the world’s land. Fertilizers, herbicides, and pesticides not only harm mycorrhizae, but they interfere with a crop’s ability to form these relationships. If the nutrients are hand delivered, why bother bartering for them with fungi?

Yes, plant and fungi symbioses are beautiful, but why should we care?

Because in healthy soils, plants exude roughly ⅓ of their carbon-packed photosynthates into the soil to lure soil life to their roots.

We need fungi lured by photosynthates to put this carbon from the atmosphere back into the soil.

On average, Soil Organic Matter (i.e. carbon) has already been reduced by roughly half in agricultural soils. Fertilizers speed up the decay of organic matter, releasing carbon into the air. Tillage that does not return ample biomass into the soil will oxidize the organic matter that is there. We must give back more than we take. Real Organic farmers understand this.

Potential Global change consequences:

The potential consequences of changes in arbuscular mycorrhizal communities are depicted well in the image below:

A diagram showing at the center "AM Fungal Community" and connected around it multiple connected issues. From top center clockwise: "Plant disease resistance", "Crop Yields", "Plant Stress Resistance (eg drought)", "Global carbon and nutrient cycles", "Other soil microbiota (eg nodulating bacteria, collembola)", "Soil stability", "Plant growth", and "Plant communities"

Source: FEMS Microbiol Ecol, Volume 94, Issue 11, November 2018.

Organic Farming is Carbon Farming

It is called organic farming for a reason. Organic chemistry is the chemistry of carbon

Organic farming is the farming of carbon.

Real organic farmers replace fertility in the form of slow-release compost, mulch, and incorporated cover crops.

Slow-release fertility does not interfere with a crop’s ability to form underground partnerships, because the nutrients are not readily available. They are locked up in the organic matter.

So the crop must feed the soil with its photosynthates to attract microbes to unlock the nutrients for them.

Our challenge is to support and incentivize Real Organic agriculture so we can reverse the loss of carbon from the soil.

Without soil, it is not organic farming.

There is so much essential beauty in the underground, and we are losing it before we even begin to understand it.

Yours in the dirt,
Linley

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