B: Mycorrhizae: The Symbiotic Relationship between Fungi and Roots - Biology LibreTexts
Mycorrhizae are symbiotic relationships that form between fungi and plants. The fungi colonize the root system of a host plant, providing increased water and. Mycorrhizal fungi belong to several taxa and develop mutualistic symbiotic associations with over 90% of all plant species, from liverworts to angiosperms. A mycorrhiza is defined as a symbiotic relationship between the roots of plants and fungi. The term mycorrhiza literally means root fungus, but in the broad sense.
The Mutualistic Interaction between Plants and Arbuscular Mycorrhizal Fungi.
No one made much of the findings for decades afterward, because botanists took them to be examples of fungi parasitizing plants. A contemporary gave it the name mycorrhiza, Latin for fungus-root.
Say it with me: The plural is mycorrhizae: Symbiotic Relationships At least 80 percent of the plant species on the globe, representing more than 90 percent of all the plant families, are known to form mycorrhizae.
- WHAT ARE MYCORRHIZAE?
- 31.3B: Mycorrhizae: The Symbiotic Relationship between Fungi and Roots
In addition to facilitating the transportation of nutrients, at least one kind of mycorrhizal fungus attracts and kills the tiny soil-dwelling arthropods called springtails, a rich source of nitrogen. Other carnivorous fungi capture the superabundant microscopic worms known as nematodes, either with sticky knobs that develop from the hyphae, fine filament meshes, or loops that constrict to snare passing prey — fungal lassoes.
A variety of mycorrhizal fungi protect plant associates from root-devouring nematodes by producing chemicals lethal to the worms, nematicides, which have drawn interest from the agricultural pest control industry. Many mycorrhizal fungi secrete antibiotics fatal to bacteria that infect root systems. Not surprisingly, those chemicals have generated close interest among researchers, too.
The more vigorous a plant, the better it can contend with diseases and parasites, compete for space and sunlight, invest extra energy in the production of flowers or cones, successfully reproduce, and replace growth lost to insects, larger grazing animals, storm breakage and seasonal defoliation. Engaging in a symbiotic relationship with fungi is clearly a winning combination for plants, and the connections reach more widely than you might suppose. They have also found mycelia with hyphae connecting different species.
For example, a cluster of conifer saplings arising from a dark forest floor and struggling upward toward the light needs nitrogen to continue building tissues. But if one of the young conifers can get an infusion of that element through hyphae linked to an alder or birch tree, whose roots host symbiotic nitrogen-fixing bacteria, that particular sapling may be good to go.
Make that good to grow.
Mycorrhizal Fungi and Plant Roots: A Symbiotic Relationship
If hyphae from the impoverished plant only reach the soil near the second plant, this can be enough. Some farmers might have guessed that the roots of one plant borrowed good stuff from the soil around another, but nobody was aware of the bacteria in nodes on the legume roots making the nitrogen available or aware of the mycorrhizal hyphae gathering it.
They just knew the maize grew better. They offer packets and jars of inoculants to treat roots or seeds prior to planting and larger quantities for broadcasting onto croplands, especially those whose mycelial structures have been disrupted by chemical treatments, over-tilling or compaction from trampling.
To learn more gardening with mycorrhizal fungi in mind, read Mycorrhizal Fungi: It will be a microbe, single-celled algae or else cyanobacteria, which can convert sunlight to energy as well. Some fungi partner with both types at once. As in a mycorrhiza, the fungus takes a share of the sugars produced by its solar-powered collaborator.
Cyanobacteria also fix nitrogen, making that available to any resident algae as well as to the fungus.Mycorrhizal Symbiosis
The fungus meanwhile shelters the partner cells nested among its filaments and keeps them moist by absorbing water from rain, mists, and dew. Swiss botanist Simon Schwendener proposed in that this combination of creatures represented a symbiotic relationship. It earned him years of scorn from prominent lichenologists. It was more like a creed — a projection of the human sense of individual identity in Western culture.
As ofthousands of species of lichens have been identified.
Mycorrhizal Fungi and Plant Roots | MOTHER EARTH NEWS
Their nature as a sort of biological alloy makes them tremendously self-sufficient and able to inhabit extreme environments. Lichens from Antarctica survived 34 days in a laboratory setting designed to simulate the environment on Mars. For that matter, lichens have been shot into orbit and placed outside a spacecraft in a container that was then opened, directly exposing those composite creatures to the flash-freezing temperatures and cosmic radiation of space for 15 days.
The fungus obtains nutrients, such as sugars, from the plant root. Mycorrhizae help increase the surface area of the plant root system because hyphae, which are narrow, can spread beyond the nutrient depletion zone.
Hyphae are long extensions of the fungus, which can grow into small soil pores that allow access to phosphorus otherwise unavailable to the plant. The beneficial effect on the plant is best observed in poor soils.
All about Mycorrhizae, its benefits, application and research and development
The benefit to fungi is that they can obtain up to 20 percent of the total carbon accessed by plants. Mycorrhizae function as a physical barrier to pathogens. They also provides an induction of generalized host defense mechanisms, which sometimes involves the production of antibiotic compounds by the fungi.
Fungi have also been found to have a protective role for plants rooted in soils with high metal concentrations, such as acidic and contaminated soils.
Hyphae proliferate within the mycorrhizae, which appears as off-white fuzz in this image. These hyphae greatly increase the surface area of the plant root, allowing it to reach areas that are not depleted of nutrients. There are two types of mycorrhizae: Ectomycorrhizae form an extensive dense sheath around the roots, called a mantle.
Hyphae from the fungi extend from the mantle into the soil, which increases the surface area for water and mineral absorption. This type of mycorrhizae is found in forest trees, especially conifers, birches, and oaks.