A DEDICATED GROUP of mycologists has made a tremendous amount of progress in advancing the understanding and importance of mycorrhizae. These scientists have demonstrated that mycorrhizae are not only critical to life on Earth, but that mycorrhizal fungi are beautiful and mind-blowing in their function and form. What was once thought to be a lone and supposedly pathogenic fungus has become a multitude of species bearing nothing but benefits.
Continuing discoveries that contribute to our knowledge of mycorrhizal fungi offer the promise of an interesting, even brighter, future. Given the many problems we’ve created and now face with soil degradation and erosion, not to mention reduction in phosphorus production as reserves are depleted, we’d be crazy not to welcome the relief mycorrhizae offer with open arms. And with the many ecological impacts of mycorrhizae, we can solve problems biologically rather than by using chemical solutions with deleterious results. As mycorrhizal propagules become less expensive to produce, with better viability and delivery systems, they are becoming economically practical for every application—from forest, to cropland, to nursery, to home garden.
Studies have revealed specific protein transporters that enhance the ability of mycorrhizal fungi to absorb heavy metals, including radioactive toxins. They sequester these toxins within their cells, or the host plant can use carboxylic acids, such as citric, malic, and malonic acids, to sequester heavy metals in leaf vacuoles. Reforestation efforts following tree harvest, fires, or removal of minerals can also benefit from the reintroduction of mycorrhizal propagules into forest soils. In nutrient-poor and water-deficient forest environments, mycorrhizal fungi play an important role in helping recently planted trees absorb more nutrients and moisture from stressed soils, increasing growth and improving overall forest health.
Biochemical and molecular studies may prove helpful for genetically improving mycorrhizal fungi that can be adapted to handle a variety of problems associated with plant health in the forest as well as the field. As warming temperatures around the globe impact agricultural production and water availability, mycorrhizal fungi can be useful in introducing new plants to new climate zones or in maintaining existing plants in changing zones, helping them to adapt. In addition, the impacts of drought can be mitigated by mycorrhizae that extend to access underground reserves of water that plant roots alone cannot reach.
The glomalin glycoprotein created by arbuscular mycorrhizal fungi may act as an important carbon sink in productive soils. As some of the carbon dioxide consumed by plants is transferred to their mycorrhizal fungi as glucose from photosynthesis, much of it is eventually turned into glomalin, which is stored in the soil for many years before it biodegrades. The sticky glomalin also improves soil structure and reduces soil erosion and compaction by helping soil form aggregates to improve soil porosity. These soils can store more air and water to benefit healthy growth of roots and important soil microbes.
We are better able to identify mycorrhizal fungi using DNA and RNA sequencing, giving us a leg up in identifying fungal varieties and their associations with particular host plants. Work in the field of fungal genetics is leading to the creation of tailor-made, perhaps even condition-specific, mycorrhizae. As new techniques improve spore production and results are demonstrated in the field, use of mycorrhizal fungi will become the norm.
We still have a tremendous amount to learn about mycorrhizal fungi and mycorrhizae. We know that other organisms work with mycorrhizal fungi in the mycorrhizosphere, but we have yet to identify them all and understand exactly how they work. When A. B. Frank identified mycorrhizae and explained their role some 150 years ago, he could only guess at their importance. Now that we know, it is time to use this knowledge.