There is a fungus among us!

For over four hundred million years, arbuscular mycorrhizal fungi have been forming symbiotic relationships with plants around the globe. Found on almost every continent and in approximately 80% of vascular plants, these important fungi play a pivotal role in plant nutrient uptake in diverse ecosystems.

These important fungi begin their life in the soil – in the area where roots can grow. Plants release hormones that helps the fungi grow. The plants release the hormones to increase the chance of a root-fungi interaction.

Plants seek to interact with arbuscular mycorrhizal fungi to create a mutually beneficial relationship. Once the fungi and plant roots meet, the fungi penetrate the root cells. From there, the fungi create and establish incredible structures called arbuscules, which were named for their tree-like structure.

Image of arbuscular mycorrhizal fungi within a cotton root sample under optical microscope (160X magnification). The balloon-like structures are called vesicles. Vesicles are arbuscular mycorrhizal fungi’s storage structures. The lines extending from the vesicles are the hyphae of the arbuscular mycorrhizal fungi. Credit: Hayley Crowell

Due to their many branches, arbuscules have a high surface area. This allows the fungi to efficiently exchange many different nutrients with the plant. Arbuscular mycorrhizal fungi are known for increasing uptake of phosphorous in the plants they interact with. They can also provide greater uptake of nitrogen, potassium, zinc, and more.

In exchange, the host plant provides food to arbuscular mycorrhizal fungi. The plant shares products it makes during photosynthesis, like lipids and sugars. Arbuscular mycorrhizal fungi rely on the host plant for life, but it is a small price to pay for the plant to have greater access to essential nutrients.

Meanwhile, in the soil, arbuscular mycorrhizal fungi form an extensive network of hyphae. The branched hyphal system acts as an extension of the root system. This provides greater access to nutrients that would have otherwise been out of reach. This longer, extensive hyphal system can reach into soil pores that were previously too small for the root system to explore.

Lab bench showing dye, lower left, used to stain root samples collected in the field. Sections of the root samples are then placed on microscope slides, upper right, for analysis. Credit: Hayley Crowell

Although arbuscular mycorrhizal fungi are small, they are mighty! One gram of soil can contain between one to twenty meters of hyphae. The microscopic fungi can dramatically improve nutrient uptake for its host plant. It is incredible what these fungi do for plants and, subsequently, humans.

Many researchers are exploring arbuscular mycorrhizal fungi’s role in agriculture. Important crops around the world, such as wheat, rice, corn, potato, cotton, and soybean, can form relationships with them. Finding ways to use the fungi’s impressive abilities could enable producers to meet the growing demand for food in an environmentally friendly way.

Hayley Crowell, Anna Yang, and others carefully collect cotton root samples to analyze arbuscular mycorrhizal fungi colonization rates. Credit: Audrey Gamble

Sometimes referred to as “living fertilizers,” arbuscular mycorrhizal fungi have the potential to maintain yield while reducing some need for fertilizer. These fungi boost nutrient and water uptake. They can enhance soil structure. They even have been shown to improve plant responses stresses, such as soil salinization, heavy metal contamination, and extreme temperatures.

With the known benefits, it’s no surprise that researchers are looking to further understand how to protect and take advantage of these powerful, ancient fungi to improve crop productivity in degraded soils and a changing climate.

Answered by Hayley Crowell, Auburn University

To read another blog about soil fungi, read Do Plants and Soil Really Talk.

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