Mycorrhizal Fungi - Friends of the Ecosystem

Coexisting is hard - these mushrooms make it look easy! 'Mycorrhiza' comes from the Greek roots 'mykes' (Latinized as 'myco'), meaning fungus, and 'rhiza', meaning root. Besides being fun to say, this name is a great descriptor as these fungi form symbiotic relationships with plants, connecting directly at their roots.

The broader mycorrhizal grouping can be further broken down into two major subcategories which include endomycorrhiza and ectomycorrhiza. The basic differentiator between these subcategories is the direct penetration (endo), or lack thereof (ecto), of the fungal 'hyphae' into the relational plant root. Hyphae are thread-like structures that serve as the fundamental building blocks of the larger mycelium, which functions as the fungal network as shown in the following figure.

Now that we have a few definitions out of the way, how exactly are these closely situated fungi beneficial to the plants they interact with? Here are some of the reported benefits:

• Enhanced Nutrient and Water Absorption – The extensive fungal hyphae extend beyond the plant’s root system, increasing access to essential nutrients like phosphorus, nitrogen, and micronutrients while also improving water uptake. This expanded network enhances drought resistance and ensures plants can access resources that might otherwise be unavailable.
• Improved Soil Health and Root Structure – Mycorrhizal networks enhance soil health by binding soil particles together, reducing erosion, and promoting microbial diversity. At the same time, they stimulate root branching and development, leading to greater plant stability and more efficient nutrient acquisition from the plant itself!
• Chemical Signaling & Communication – Some mycorrhizal fungi form underground networks (sometimes called the "wood wide web") that allow plants to exchange nutrients and chemical signals, even warning neighboring plants of threats like herbivory or disease.
• Disease and Stress Resistance – Mycorrhizal fungi outcompete harmful soil pathogens and trigger natural defense mechanisms. They also enhance tolerance to environmental stresses, such as salinity, heavy metal contamination, and extreme temperatures, by improving nutrient balance and reducing oxidative stress.

Now before we get too carried away with all the amazing benefits of these fungi, it’s important to note that mycorrhizal fungi are not always beneficial. While they evolved to be primarily mutualistic, they can exhibit pathogenicity under certain conditions. One other point of contention, not all mycorrhizal fungi can form associations with every plant species. Luckily, mycorrhizal fungi are certainly diverse, both phylogenetically and in terms of their differing plant partners. However, specific classes of fungi are more likely to associate with particular plant species, and these interactions are further influenced by environmental factors that impact plant survival. Below are a few examples of these pairings:

Arbuscular Mycorrhizal Fungi - A type of endomycorrhizal fungi that forms relationships with a majority of land plants:

• Most grasses (wheat, corn, rice, barley)
• Legumes (peas, beans, soybeans)
• Vegetables (tomatoes, carrots, onions, lettuce)
• Herbaceous plants (sunflowers, dandelions)
• Many shrubs and some trees (maple, ash)

Ectomycorrhizal Fungi - Mainly woody trees and shrubs:

• Conifers (pine, spruce, fir, cedar)
• Hardwood trees (oak, birch, beech, chestnut)
• Some tropical trees (Eucalyptus)

Ericoid Mycorrhizal Fungi - A type of endomycorrhizal fungi known for their distinctive hyphal coils! Relationships mainly with plants in the Ericaceae family:

• Heathland plants (heather)
• Blueberries, cranberries, rhododendrons

Now this all sounds great to me, but I want to know how we can use them! The benefits of mycorrhizal fungi are being harnessed for various applications, including sustainable agriculture, reforestation, and habitat restoration! This might be especially relevant to communities and ecosystems that have unfortunately been impacted by forest fires.

• Sustainable Farming: Farmers can incorporate mycorrhizal inoculants into their soil to reduce fertilizer dependency, improve crop yields, and enhance soil health. This may also help with some of the known fertilizer runoff problems like algal overgrowth and aquatic toxicities among others!
• Forestry and Reforestation: The introduction of mycorrhizal fungi in tree plantations can accelerate growth and increase the survival rates of saplings.
• Ecological Restoration: Mycorrhizal fungi are used to rehabilitate degraded lands by facilitating plant establishment in nutrient-poor soils.

Mycorrhizal fungi can be hugely beneficial allies in plant health, ecosystem stability, and sustainable land management. As we learn more about these symbiotic relationships, the utilization of mycorrhizal fungi in agricultural and conservation practices could pave the way for more resilient and productive ecosystems. By learning more, we can work toward a more sustainable future for both natural and cultivated landscapes. Personally, I can't wait to do my own experimentation in my future garden!

*Information presented on RxTeach does not represent the opinion of any specific company, organization, or team other than the authors themselves. No patient-provider relationship is created.

References:

Zhang W, Yu L, Han B, Liu K, Shao X. Mycorrhizal Inoculation Enhances Nutrient Absorption and Induces Insect-Resistant Defense of Elymus nutans. Front Plant Sci. 2022;13:898969. Published 2022 May 31. doi:10.3389/fpls.2022.898969

Wahab A, Muhammad M, Munir A, et al. Role of Arbuscular Mycorrhizal Fungi in Regulating Growth, Enhancing Productivity, and Potentially Influencing Ecosystems under Abiotic and Biotic Stresses. Plants (Basel). 2023;12(17):3102. Published 2023 Aug 29. doi:10.3390/plants12173102

Martin FM, van der Heijden MGA. The mycorrhizal symbiosis: research frontiers in genomics, ecology, and agricultural application. New Phytologist. 2024;242(4):1486-1506. doi:10.1111/nph.19541.