How Mycorrhizal Relationships Led to the Formation of Life on Land

Can you imagine a world without flowers, grass, and trees? It would be impossible, but that’s how it was on our planet for its first 3.5 billion years. It appears that mycorrhizal fungi facilitated their transition and enabled life as we know it today.  

Primordial plants first moved to the soil around 470 million years ago. The transition brought them significant benefits, like greater light exposure and access to carbon dioxide. They had to cope with higher UV radiation and droughts to survive, though.

Establishing symbiosis with fungi seems to have helped. A recent experiment added proof to this theory and awakened further appreciation of the fifth family. 

Keep reading to discover this ancient relationship and how it might be responsible for most existing vegetation.

What Are Mycorrhizae?

Mycorrhizae is a Latin word that translates to fungus-root. We use it to describe the symbiosis between land plants and species of mycorrhizal fungi. This relationship enables the survival of a vast majority of Earth’s vegetation.

Fungi consist of mycelium, the underground system of thread-like roots called hyphae. They sometimes contain a fruiting body with a stem and cap but predominantly stay beneath the surface. That’s also where the symbiosis occurs.

When plants and fungi cooperate, the mycelium colonizes the root system, turning it into a host. Hyphae aid moisture and nutrient absorption and protect the vegetative body from pathogens. At the same time, photosynthesis supplies the underground structure with carbs.

Mycorrhizal fungi incorporate numerous species of the mushroom kingdom. Scientists divide them into two main groups:

• Ectotrophic (ectomycorrhizae), where the mycelium doesn’t penetrate the roots
• Endotrophic (endomycorrhizae), where the hyphae enter the root cells

Ectomycorrhizae form symbiotic relationships with wood species, like birch, pine, oak, and willow. Around 10% of terrestrial plants have them, sporting a thick sheath of hyphae around the root surface.

On the other end of fungi-plant relationships, Endomycorrhizae unite with over 80% of existing plant species, including most vegetables, fruits, flowers, and grasses. These fungi establish an exchange system inside the root, forming an invasive yet highly beneficial relationship.

The trees and plants in your local park may be more interconnected than you thought.

Mycorrhizal Fungi and Plant Life

Ancient records hold the meaning of this symbiotic relationship. How does it look in practice, though? What do both life forms get from their shared connection?

The benefits stem from the ways both acquire food. Fungi are heterotrophic, so they sponge nutrients from their surroundings. Plants are autotrophic, producing carbohydrates through photosynthesis. They also need minerals from the soil, absorbing them via their roots.

Plants may struggle to soak in the essential nutrients in depleted soils. Fungi sometimes lack a stable carb source and stop stretching. A symbiotic relationship supplements scarcities in both life forms, and they thrive.

When this happens, hyphae stretch around the root zone and sometimes penetrate it. By doing so, they increase the surface area for nutrient and water absorption, reaching farther than roots would alone. Plants return the favor by supplying fungi with carbs to be used as energy.

Besides feeding both life forms, this symbiosis buffers the root zone against stress and pathogens.

Around 90% of land-based plant life depends on mycorrhizal fungi today, and fossil records of vegetation exhibit the same associations. As a result, scientists believe these fungal species are one of the contributing factors to early plant life coming onto land.

Testing the Hypothesis

A 2021 study published in Science provided the first experimental evidence for the ancient mycorrhizae hypothesis.

Scientists reasoned that primitive plants evolved and produced a new species after establishing a symbiosis with fungi. As a result, those with a common ancestor should respond similarly to their presence.

To check this, researchers compared a primitive terrestrial liverwort species with flowering plants. They discovered the groups shared genes that respond to mycorrhizal fungi. They affected the production of plant hormones, infection responses, and energy transfer for symbiosis.

The study proves that symbiosis is an ancestral trait likely responsible for blooming plant life.

Mycorrhizae Today

Mycorrhizal fungi were essential to early life and developed in most plant-bearing soils without human interference. What happens when we move cultivation to a controlled setting? Are they still as beneficial?

The short answer is yes. Mycorrhizae are valuable to any industry involving soils and plants. These fungal life forms found their way into the following fields:

• Agriculture: fungi supplement water sources and fertilizers. They increase the absorption rates of water and minerals from the surrounding soil for sustainable food production.
• Forestation: introducing mycorrhizae in the soil aids rooting. The plants establish themselves more quickly and develop higher root biomass with fungal assistance.
• Horticulture: fungi make plants grow more prosperous and vibrant. Flowers and bushes are less susceptible to pathogens and drought seasons.

Individual gardeners and amateur landscapers can also take advantage of these colonies. Introducing them into the soil makes landowners less dependent on soil-depleting chemicals. These cultivation practices could make the Earth more eco-friendly if applied on a large scale.

Fungal Past for a Better Future

The recent experiments shed light on processes long past. We’re yet to grasp each fungi-plant pairing fully, but what we know enables exceptional feats of green gardening. Besides appreciating mycorrhizae as the basis of life on land, we could use these same species to bolster, if not save, it.

Modern people might use the ancient symbiosis for gardening success today. Large-scale cultivation operations may employ the fungi to re-greenify the Earth.

Learning about this process made us fall even deeper in love with mushroom power. If you feel the same, why not advance your appreciation via amateur microscopy? Visit our shop, purchase lab-grade spore syringes, and explore the microcosm of fungal life.

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