Mycorrhizal Fungi and Plant Roots | MOTHER EARTH NEWS
Mycorrhizal fungi have existed since the first plants appeared on dry land more than million years ago. They form a close symbiotic relationship with plant. Microbiol Spectr. Dec;4(6). doi: /jingle-bells.info The Mutualistic Interaction between Plants and Arbuscular Mycorrhizal Fungi. In this symbiotic relationship, the mycorrhizal network draws nutrients from the soil for plant roots, which would sometimes be inaccessible.
Thus, roots colonized by mycorrhizae enables the plant to be better protected and to resist the stress caused by transplanting, drought and heat, while maintaining an optimal growth rate. Mycorrhizal fungi also receive benefit from symbiosis with the plant.
Due to the plants ability to photosynthesize, the plant synthesizes carbon-based substances sugarswhich feeds the fungi. You may say there is an exchange of services between the fungus and the plant.
Soils disturbed by urbanization Urban landscaping in recent years, is challenged by climate change and urban heat islands that are generated with the use of concrete surfaces in city environments. This means that the plants selected for these locations must be reviewed periodically to ensure they can survive in these landscaped areas with extreme temperatures, drought, human activity, etc.
The soil must also be considered when it comes to plant survival, as it plays a crucial part in the retention of water and health of plants, especially for trees and shrubs, whose life cycle is longer than annuals. The organic matter, microflora and other organisms, such as earthworms, are essential factors in soil fertility and play a major role in the plant establishment success. A good microbiological diversity in the soil helps maintain the soil's structure, which aids in the retention of water and nutrients.
In exchange, the fungus receives sugars and nutrients from its host plant. The main body of those species and many others typically consists of fine-branching threads known as hyphae.
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. 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.
Mycorrhiza - Wikipedia
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.
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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. 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.
The third growth spurt simply resulted in recolonization by the brown species. These events suggest that as a root grows it may continue to associate with one species of fungus but it also has the opportunity to change partners.
Numerous studies have shown that ectomycorrhizal fungi differ greatly from one another in their physiology and it is tempting to think that as a root extends out through the soil it is able to form an association with a fungus apprpriate to the particular conditions it encounters. The ability to form ectomycorrhizae is found in many families of fungi, but most commonly among members of the class Agaricomycotina of the Basidiomycota, especially those producing mushrooms and boletes.
Mycorrhizae and Plants Make Great Allies | PRO-MIX
Most of the larger mushrooms you see in the forest have arisen from the networks of extra-radicular hyphae permiating the soil beneath your feet. The abundance of these mushrooms, their sheer weight and volume, attests to the magnitude of their activities. The energy and chemicals needed to build these mushrooms comes in great part from the trees, suggesting that the advantages a plant gains from mycorrhizae come at a cost.
Most plants exclusively form arbuscular mycorrhizae but there are compelling reasons to focus attention on those having ectomycorrhizae as well.
31.3B: Mycorrhizae: The Symbiotic Relationship between Fungi and Roots
Although a smaller number of species are involved, ectomycorrhizae dominate in the pine, oak, birch, willow, walnut and several other families. In the tropics these include the dipterocarps and large woody legumes.
In New Brunswick our extensive forests of spruce, fir, white pine, birch and poplar support immense continuous networks of ectomycorrhizal fungi. Without these fungi our forests as we know them would not exist. Thus the ecological and economic importance of ectomycorrhizae cannot be overestimated. Many biologists have noted the major differences between tropical and temperate forests and have attempted to relate these to dominance by certain mycorrhizal types.
The pictures above illustrate two such forests; at left a tropical rain forest in northern Costa Rica and at right a forest near Schefferville, Quebec. The Costa Rican forest is dense and made up of a great variety of tree species.