Mycorrhizae: “I’m a fun-guy”
Mycorrhizal fungi filaments and bound soil particles on the root tip of a garlic plant. (Photos by Faith Forry)
Molds, yeast, mushrooms, toadstools— all organisms which constitute the fascinating kingdom of Fungi. Fungi are eukaryotic organisms (having cells that store DNA inside a nucleus) that are distinctly unique from plants and animals. While fungi have cell walls (like plants’ cells), they lack roots, vascular tissue, and chlorophyll. Despite their differences, one could easily assume that plants and fungi are closely related; however, research has interestingly found that fungi are more closely related to the animal kingdom than to Kingdom Plantae.
Fungi are heterotrophic organisms, meaning they uptake organic materials from an outside source; in contrast, autotrophic organisms create their own nutritional organic substances from simple inorganic substances. Autotrophic plants create carbohydrates through the process of photosynthesis; heterotrophic fungi absorb organic matter and nutrients from their surroundings. Thus, while fungi can readily absorb essential nutrients like phosphorus and nitrogen, plants can struggle to acquire these nutrients. This is a predicament for which nature has evolved a miraculous solution.
Hidden underground are incredible networks of mycorrhizal fungi which connect and colonize the roots of plants. Mycorrhizal fungi form a symbiotic relationship with these host plants; specifically, ectomycorrhizas are extracellular mycorrhizae which enclose root cells but do not penetrate them. The branching, threadlike filaments of the fungi (called the hyphae) greatly increase the area from which water and nutrients can be absorbed, essentially multiplying the expanse of a plant’s roots. Ectomycorrhizas can accumulate nitrogen for their host plants even in unideal soil conditions, allowing their host plant to survive in harsher conditions and providing it with an adaptive advantage over non-colonized competitors. Similarly, research has found that colonized plants have 40% higher phosphorus concentrations than their non-colonized counterparts. In turn, the host plant provides the fungi with an excess of carbohydrates which it created through photosynthesis. Through these incredibly intertwined connections, the mycorrhizal fungi can actually redistribute resources to provide different plants with the nutrients and water they may be otherwise lacking.
Through mycorrhizal connections seen in fossil records, it is believed that mycorrhizae have contributed to the formation and proliferation of plants on land. Though they are inconspicuously working in the soil beneath our feet, mycorrhizal fungi are responsible for the survival of most of the plants found on land. Shockingly, about 90% of all vascular plants on land live with some connection to mycorrhizae. Unknowingly, you have undoubtedly enjoyed the consequence of mycorrhizae at work. Eating blueberries, sitting under the shade of an oak tree, adorning an evergreen with Christmas ornaments-- you can thank mycorrhizal fungi for all of these pleasures and countless others.
As remarkable as mycorrhizae are, the discovery of mycorrhizal fungi and their ecological function is relatively recent, so there is certainly still much more to research and marvel. To continue reading about the symbiotic relationship between mycorrhizal fungi and plants, visit https://sciweb.nybg.org/science2/hcol/mycorrhizae.asp.html by The New York Botanical Garden.
Written by Faith Forry — July 7, 2021
