Mycorrhizal Fungi and Plant Symbioses
  • The meaning of mycorrhizal fungi comes from "myco" meaning fungal and "rhiza" meaning root. Mycorrhizal fungi are fungal organisms that live in the soil and form symbiotic relationships with host plants. Most relationships or symbioses are considered a form of Mutualism (where both species have a clear benefit) because as the host plant provides a consistent source of energy, in the form of a fixed carbon source, the mycorrhizal fungi provide extra nutrients from the soil tothe plant that would otherwise be unavailable. This happens by the mycorrhizal fungi extending the nutrient depletion zone and also improving nutrient uptake in nutrient poor soils. However, other relationships exist where the host plants are harmed by this relationship and the mycorrhizal fungi act as a parasite of sorts, taking the protection and energy sources provided by the host plant without providing the nutrients that the plant usually depends on to survive and reproduce.
  • There are two main types of mycorrhizal fungi: Ectomycorrhiza, which are intercellular fungi - what most people typically know as fungi (like truffles, mushrooms, and other large above-round fungi) and Endomycorrhizae, which are intracellular fungi - create subterrainean linkages of their hyphae to connect the host plants with as much soil as possible. Endomycorrhizae can further be categorized as: 1) Vesicular Arbuscular Mycorrhiza {VAM or AM} 2) Orchidaceous and 3) Ericaceous.
Entoloma_moongum_-_Ectomycorrhiza.jpg
Ectomycorrhiza (Entoloma moongum)
Glomus_versiforme_-_VAM.jpg
Endomycorrhiza (Glomus versiforme)

  • Most plants are obligate symbionts with the mycorrhizal fungi (70 to 90% of all land plants to VAM) however, most are not host specific and the vast majority of mycorrhiza haven't been fully studied, especially when dealing with the symbiotic relationships they are able to form with countless land plants.
  • A very common, and non-host specific phylum of endomycorrhizae is Glomeromycota (Glomus spp.). A specific example of fungi from this phylum is Glomus claroideum, forms a mutualistic symbiosis with a perennial, herbaceous plant species Antennaria dioica. This relationship is one of the many common symbioses formed between endomycorrhizae and vesicular plants and proves to be a great example for this general relationship because the host plant benefits incredibly in terms of growth (total biomass can be seen to have dramatic increases) because the fungal hyphae are very successful in absorbing nutrients (in particular phosphorus) from the soil that the plants roots would normally be unable to obtain.

3608-antennaria-dioica-rubra-kocianek.jpg
Antennaria dioica
glomus_clariodeum_spore.jpg
Glomus claroideum spore



  • The video below will help to show exactly how mycorrhizal fungi work and how they absorb nutrients from the soil to be then transferred into the plant root system.



´╗┐Economic Interests in Mycorrhizal Fungi
  • Since approximately 70 to 90% of all land plants are obligate symbionts with mycorrhizal fungi, which means that they rely on the presence of the fungal symbiont to be able to reproduce, people have taken notice of the immense benefits received in terms of plant growth and health when they have been introduced to the mycorrhizal fungi.
  • Agriculture benefits greatly when people or companies intentionally create this symbiotic relationship because it allows them to grow bigger and fuller crops (of higher yield) which are also more resistant to diseases, because plants that have this fungal symbiont have been studied and seen to have an increased resistance to diseases and parasites.
  • In addition to farmers and bigger businesses utilizing this incredibly valuable natural relationship to their benefit, mycorrhizal fungi have even found their way into the "Green Movement." Using this symbiotic relationship is not only a great was to get larer crops and plants because more nutrients are available tothe host plants, but the mycorrhizal fungi are a completely natural, non-harmful, and renewable fertilizer of sorts. They are a sustainable resource that does not have to be manufactured (which would add to the ever-increasing Green-House Gases accumulating in the atmosphere) which also has none of the other harmful effects on the environment that synthetic fertilizers often times do (espcially in situations where run-off and can contaminate huge areas during storms, floods, etc.)

  • Businesses are taking advantage of this useful and beneficial relationship by using mycorrhizal fungi: in sustainable agriculture models, using it as a biocontrol agent, to help against erosion (having a larger root system will help to hold onto more soil from being erroded away), and also to help reduce the stresses of drought when it does occur.


Supplemental Information and Links



´╗┐References

  • Mycorrhizal Applications Inc. http://www.mycorrhizae.com/
  • Mycorrhizal Associations: The Web Resource. http://mycorrhizas.info/vam.html
  • Jeffries et al. "The contribution of arbuscular mycorrhizal fungi in sustainable maintenance of plant health and soil fertility." Biology and Fertility of Soils, Vol. 37, Number 1, 1 -16; October 2007.
  • Tahat et al. "Mycorrhizal Fungi as a Biocontrol Agent." Plant Pathology Journal, Vol. 9, Issue 4; 2010.
  • Varga, S. "Sex-Specific Responses To Mycorrhiza In A Dioecious Species." American Journal of Botany, Vol. 95 (10); 2008.