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- 🌱 Nearly 80–90% of land plants form partnerships with arbuscular mycorrhizal fungi.
- 🌍 AM fungi helped early plants colonize land 450 million years ago. This was very important.
- 💡 Studies show up to 80% of a plant’s phosphorus comes through AM fungi partnerships (Smith & Read, 2008).
- 🚜 Adding AM fungi to crops can cut fertilizer use by 30–50% while keeping or improving yields (Hijri, 2016).
- 🔄 Mycorrhizal networks move nutrients and chemical signals between different plant species underground.
We tend to think of ecosystems in terms of animals and plants, but fungi are important parts below the surface. Long before humans learned to farm, fungi teamed up with plants to exchange needed nutrients underground. One of the oldest and most important of these partnerships is the arbuscular mycorrhizal (AM) symbiosis. These tiny fungal allies do more than help plants grow; they helped plants get established on land. We will look at how AM fungi affect ecosystems, help crops grow, and show how varied life is.
What Are Arbuscular Mycorrhizal (AM) Fungi?
Arbuscular mycorrhizal fungi, from the phylum Glomeromycota, are tiny organisms that live in the soil. They form one of nature's most important partnerships – a relationship where both benefit – with the roots of most land plants. The main feature of these fungi is that they form special structures called arbuscules inside root cortex cells. These tree-like networks inside plant roots are made to get the most nutrient exchange between both partners.
Unlike many fungi that live on their own or feed on decaying matter, AM fungi need living plants to survive. This means they cannot grow fully without a host plant. If there are no plant roots to live on, they cannot survive. These fungi make more of themselves using spores. Spores sprout and look for new root hosts. When a root is found, a complex process starts. This creates a very special plant partnership structure, which is one of a kind.
450 Million Years of Symbiosis
The story of arbuscular mycorrhizal fungi is not just long; it is very old. Fossils from 450 million years ago show AM fungi partnered with the first known land plants (Redecker et al., 2000). These fungal companions came before flowering plants by hundreds of millions of years. They are seen as main partners in one of Earth's most important changes: when plants started growing on land.
At that time in Earth’s history, early plant life had trouble living in rocky places with little food. Pioneer plants did not have developed root systems. This meant they could not get minerals and moisture from the soil. AM fungi reached into places with many minerals and sent nutrients to their plant partners. This cooperation started how land ecosystems would grow. The success of land plants – and also animals and humans later on – could not have happened without these ancient fungi.
Nutrient Trading Beneath the Soil
The main job of arbuscular mycorrhizal fungi is to create wide networks of threads under the ground. These thread-like parts go far beyond what a plant's own roots can reach. They go into the soil to find important nutrients – especially phosphorus, nitrogen, and small amounts of zinc and copper. These are elements that are often spread out thinly in the soil.
Once taken in, these nutrients move along the fungal threads right into the plant’s root center, through the arbuscules. In return, the fungi get up to 20% of the sugars the plant makes using sunlight. This is an important energy source. This trade system benefits both: the plant gets needed minerals, and the fungi get a steady supply of carbon (Smith & Read, 2008).
In places with little phosphorus – and there are many such places – this nutrient exchange is not just helpful; it is essential. In fact, in some farms and natural areas, up to 80% of the phosphorus a plant takes in is handled by the mycorrhizal path (Smith & Read, 2008).
The Special Structure of Arbuscules
The word "arbuscular" comes from the arbuscules the fungi form inside root cells. These arbuscules are thinly branched, always changing structures that are very important in the partnership. They make the surface area for nutrient exchange bigger, just like the alveoli in the lungs make gas exchange work best. The arbuscule’s close position inside the root center allows exact movement of ions and carbohydrates between plant and fungus.
Unlike structures that last a long time, arbuscules are short-lived. They work for a few days before breaking down and are always being replaced. This constant change helps keep things working well and lets them react to changes in the environment. This makes sure the nutrient partnership is efficient and active. The structure also shows the close chemical talk and joint development that has made this partnership what it is over hundreds of millions of years.
Mycorrhizal Networks: The Underground Internet
Imagine a network for sharing communication and nutrients that can cover whole forests. That is what the Common Mycorrhizal Network (CMN) does. Through these linked fungal webs, AM fungi can connect the roots of many plants, even different kinds of plants. The result is an underground social network for plants.
These networks help move resources like water, carbon, and minerals between plants. They can also send chemical messages. For example, if one plant is attacked by pests or not getting enough water, nearby plants connected through the same network may "hear" the warning and start their defenses.
Research shows that about 80–90% of vascular land plants are partnered with mycorrhizal fungi (van der Heijden et al., 1998). Through the CMN, young plants can get nutrients from older plants, helping the next generation grow well. This shows that old ideas about plants competing are not always true. Instead, it shows a complex web of plants working together beneath our feet. This makes ecosystems stronger and more stable.
AM Fungi vs Other Fungal Partnerships
The fungal world is very varied, and not all mycorrhizal partnerships are the same. Arbuscular mycorrhizal fungi are different from other types of mycorrhizal fungi like ectomycorrhizae, ericoid, and orchid mycorrhizae.
Ectomycorrhizal fungi, for example, wrap root tips in a cover. They send their threads into the soil but do not go inside plant root cells. These partnerships are common in forest trees like oak, beech, and pine. Orchid mycorrhizae, though, are needed for orchid seeds to sprout and live. And ericoid mycorrhizae are made for acid soils and plants like blueberries.
AM fungi are different because they are found everywhere and must live with plants. Ectomycorrhizal fungi can live on their own, breaking down dead stuff or making mushrooms. But AM fungi need plant hosts completely. This makes their job in nature more special. It is also directly linked to how well plants grow, especially in grasslands, farm soils, and warm, wet places.
Soil Health Beyond Host Plants
AM fungi help more than just single plants. They also help the whole soil environment. Through their thread networks, they make soil structure better by helping particles clump together. This is when soil particles stick together to form bigger clumps. These clumps make the soil hold more air and water, let roots grow through it better, and resist washing away.
Fungal threads also release a sticky protein called glomalin. This protein is very important for how soil holds carbon and its structure. By helping keep organic matter stable and putting carbon deep in the soil, AM fungi are part of Earth's big cycles of life and chemicals. They do this by helping fight global warming. They lock carbon in the soil and help the tiny living things that are needed for soil life.
And AM fungi create a better place to live for helpful soil animals and microbes. This increases how many different living things are there. It also makes ecosystems stronger against problems like drought, diseases, and damage.
How Plants and AM Fungi Communicate
The start of this plant-fungus partnership is not random at all. Before fungi move into plant roots, a complex chemical talk happens. Plants release strigolactones. These are chemical messages that spread into the soil to attract nearby AM fungal spores. In response, fungi make Myc factors, which are also signaling molecules. This chemical talk turns on special genes in both organisms. This starts the making of arbuscules.
This communication decides if a fungus will start living on roots. It also helps stop bad interactions or disease. It’s like a compatibility test. This makes sure only fungi that help the plant and are recognized by it can get in.
This careful process shows that what looks like a simple underground trade is actually a smart and well-controlled partnership. Over time, these signaling pathways have been kept and made better. This shows how old and important the AM partnership is (Parniske, 2008).
Can We Grow AM Fungi?
You cannot grow arbuscular mycorrhizal (AM) fungi on your kitchen counter the way you would cultivate mushrooms in Mushroom Grow Bags or a Monotub. AM fungi require living root tissues to survive, so they depend on plant hosts. This means they cannot be grown like other fungi in normal lab dishes or home cultivation setups.
However, research labs have been able to isolate and grow them using specialized root-organ cultures. This method takes a lot of work, but it makes it possible to produce useful fungal products for farming and gardening.
Commercial AM fungi products are now becoming widely available for farmers and gardeners who want to improve soil health in a natural way. These products are usually made from spores or root fragments colonized by the fungi. You can apply them to young plants or mix them into potting soil to help roots absorb nutrients better.
AM Fungi in Agriculture and Permaculture
There are growing worries about soil health, relying on chemical fertilizers, and damaged ecosystems. Because of this, AM fungi are becoming more popular in farming that rebuilds soil. They can increase nutrient uptake, stop soil from washing away, and make plants healthier. This offers a strong natural way to grow crops without harming the Earth.
Studies show that adding mycorrhizal fungi can reduce chemical fertilizer use by 30–50%. This is especially true for phosphorus-based fertilizers, which cannot be replaced and harm the environment (Hijri, 2016). Crops grown with AM fungi often show they are better able to handle stress, have stable yields, and resist diseases.
Permaculture systems copy natural processes in nature. In these systems, using AM fungi helps soil rebuild, increases different kinds of life, and makes things productive for a long time. Combining AM fungi with no-till farming, green manures, and cover cropping strategies makes microbes stronger and increases plant variety. This makes systems that produce a lot and keep nature in balance.
Why Mushroom Growers Should Care
Even for people who grow mushrooms like oyster or lion’s mane, learning more about arbuscular mycorrhizal fungi helps us understand more about how fungi live in nature. It makes us look past just mushrooms into soil science, farming, lasting ways to live, and plant partnerships.
Mushroom kits of the future may include AM fungal products meant to improve plant health in companion planting or tree-based farming systems. Knowing more about fungi – not just the fancy eating ones – helps growers, gardeners, and scientists see things more broadly.
By learning to appreciate mycorrhizal fungi not just as farming tools but as things that make ecosystems what they are, both hobby growers and professional plant growers can help rebuild soil health starting from the very bottom.
References
- Hijri, M. (2016). Analysis of the impact of arbuscular mycorrhizal fungi on plant productivity and yield. Mycorrhiza, 26(7), 631–640.
- Parniske, M. (2008). Arbuscular mycorrhiza: the mother of plant root endosymbioses. Nature Reviews Microbiology, 6(10), 763–775.
- Redecker, D., Kodner, R., & Graham, L. E. (2000). Glomalean fungi from the Ordovician. Science, 289(5486), 1920–1921.
- Smith, S. E., & Read, D. J. (2008). Mycorrhizal Symbiosis. Academic Press.
- van der Heijden, M. G., et al. (1998). Mycorrhizal fungal diversity determines plant biodiversity, ecosystem variability and productivity. Nature, 396(6706), 69–72.
Want to look deeper into the fungal world? Check out our latest collections and resources at Zombie Mushrooms — where nature's partnerships come to life underground and beyond.
