Over the past few decades, there has been an increasing interest in the identification and cultivation of beneficial soil microorganisms. It is widely documented at this point that many bacteria, fungi, and other microorganisms can help plants in combatting disease, making essential nutrients available and acquiring water in when it’s short in supply. Within this group of beneficial microorganisms exists a group of fungi called mycorrhizae. These fungi can grow in a symbiotic relationship with most plants and have been investigated as growth and quality enhancement tools for agricultural and horticultural crops.
Most mineral soils in North America contain some trace of mycorrhizal fungi, but rarely at levels that would allow for proper colonization. Mycorrhizae are host specific and will only colonize certain plants, so in some soils there won’t be any native mycorrhizae that will benefit these plants. For instance, plants in the brassica family rarely form relationships with mycorrhizae. Most plants would benefit from an addition of mycorrhizae to the soil.
What are mycorrhizae?
The term mycorrhiza (singular) means “fungus root” and describes the symbiotic relationship between fungus and plant root. The relationship between fungus and plant begins when fungal spores germinate and create threadlike structures called hyphae which enter the epidermis or outermost layer of cells of the plant root.
Image: Fungal hyphae interacting with plant root cells
Once the plant root is colonized, the fungus will disperse a vast but dense network of hyphae throughout the soil to greatly increase the absorptive area of the fungus. Once the network of hyphae is extended, plants will generally improve their ability to uptake nutrients and water as the fungus acts as an extended root system for the plant. It’s been observed that mycorrhizal fungi will almost always improve the intake of phosphorus, zinc, manganese and copper into a plant.
Types of Mycorrhizae
The classification of mycorrhizae is based on the inter-relation of fungal hyphae to plant root cells. Ectomycorrhizae form a network of hyphae that do not penetrate the root cells but instead colonize the outer surface of roots. Ectomycorrhizal fungi can reproduce without the presence of a plant host.
Endomycorrhizae form an association where the hyphae penetrate and colonize inside of the plant root cells. Once the roots are colonized, individual hyphae extend from the root and branch out into the soil to find nutrients and water. Once enough hyphae have formed, a vast network of hyphae will dramatically improve the plants' ability to absorb nutrients and water from the network of hyphae. The plant will trade sugars and carbon created through photosynthesis for nutrients made available by the hyphae. About 85% of plant families can form a relationship with endomycorrhizae, including most seed-bearing plants, rain forest tree species, most agricultural crops and a vast majority of ornamental greenhouse crops.
Image: Difference in establishment between ectomycorrhizae and (arbuscular) endomycorrhizae.
As Endomycorrhizae are the most common type of mycorrhizae that are mentioned in agriculture, we’re going to focus on that for the remainder of the article. Endomycorrhizae are named based off of one of three structures they form:
1. Arbuscules: Two to three days after colonizing a plant root cell, hyphae will form structures within plant cells called Arbuscules, which resemble small trees and facilitate the transfer of nutrients within plant cells. Arbuscular mycorrhizae provide the plant with nutrients and water from the soil while the plant provides sugars and carbohydrates for the fungus.
2. Vesicles: These structures are formed between the cells and act as storage organs for the fungi.
3. Spores: endomycorrhizal fungi also produce spores, which serve a similar function as plant seeds do. Spores have thick walls, resist freezing and intense heat, and can survive for long periods of time until germinated.
Growth Benefits of Mycorrhizae
Applications of endomycorrhizae can be greatly beneficial for intensely farmed land, new housing developments and gardens where the topsoil has been disturbed or stripped away, and other areas where the overuse of chemical fertilizers and lack of organic matter inputs has left the soil bare of microorganisms.
Image: Plant root colonized by endomycorrhizae with hyphae visible.
Additionally, endomycorrhizae is especially useful for plants that are commonly subjected to stressful growing environments like arid conditions, unseasonal temperatures, excessive chemical fertilizer use, and establishment of new plantings. For example, vineyards would benefit from endomycorrhizal applications as the grapevines are often kept in a state of stress to improve the quality of fruit.
The benefits of using endomycorrhizal fungi can include but are not limited to:
Reduced nutrient deficiencies
Reduction in input usage
Faster and larger plant growth
Resistance to soil salinity
Reduced prevalence of root diseases
Increased number of flowers and fruits
Image: Herb roots without mycorrhizae (left) and with mycorrhizae (right)
The goal of using mycorrhizae in agriculture is to reduce the amount of non-growing work the plant has to do, so it can focus it’s time and energy on growing tall with as many fruits as possible.
Nurture Growth Bio-Fertilizer
We have recognized the power of endomycorrhizae and include a strain of arbuscular mycorrhizae, along with other powerful microorganisms, in our flagship biofertilizer. I invite you to read testimonials from our clients on our commercial testimonial webpage.
If you’re interested in the benefits that mycorrhizae can bring to your crop, please reach out to one of our team members for a quick conversation at firstname.lastname@example.org.
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Eric is a gradate of the Environmental Science program at the University of Toronto. Coming from the green roof and landscaping industries, he does not hesitate to get his hands in the soil. He is actively searching for new ways to learn about our agricultural systems and get involved with his local agricultural community. Eric is an avid birdwatcher and advocate for environmental responsibility.