John Miller
Mycorrhizae are symbiotic associations between fungi and plants, with the fungus colonizing the host plant's root tissues. They are ancient, potentially as old as the terrestrialization of plants, and are crucial in plant nutrition, soil biology, and soil chemistry. Mycorrhizae increase the absorptive area of a plant, acting as extensions to the root system, and are particularly important in the case of phosphorus. Mycorrhizal mushrooms are mutualistic fungi that form symbiotic relationships with plants and trees, with the fungi using their underground mycelial network to interact with the roots of the plants or trees. While not all mycorrhizal fungi grow mushrooms, those that do typically form associations with woody trees and shrubs.
| Characteristics | Values |
|---|---|
| Definition | A symbiotic relationship between a fungus and a plant |
| Types | Ectomycorrhizae and endomycorrhizae |
| Sub-types | Arbuscular, ericoid, orchidaceous, ectendomycorrhizas, ericoid endomycorrhizas, monotropoid endomycorrhizas, arbutoid endomycorrhizas |
| Benefits | Access to a large amount of water and nutrients, increased root surface area of absorption, protection against root diseases |
| Application | Direct infection of cuttings or plugs, incorporating into the media or the soil, applied through irrigation |
| Plants that do not respond | Azalea, beet, blueberry, broccoli, Brussels sprouts, cabbage/kale, carnation, cauliflower, collards, cranberry, heath, huckleberry, mustard, protea, rhododendron, sedge and spinach |
| Plants that respond | Almost all plants, especially woody plants and trees |
| Number of species | Several thousand |
| Age | 400-500 million years old |
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What You'll Learn
Mycorrhizal fungi are ancient
Mycorrhizae are ancient symbiotic associations between fungi and plants. Fossil and genetic evidence indicates that mycorrhizae are ancient, potentially as old as the terrestrialization of plants. The evolution of mycorrhizae is linked to the evolution of terrestrial flora, with evidence suggesting that they evolved alongside terrestrial plants approximately 450-500 million years ago. This is supported by the discovery of arbuscular mycorrhizae in the 400-million-year-old Rhynie chert, which provides a lower bound for the development of mycorrhizal symbiosis.
Arbuscular mycorrhizae are the oldest and most common type of mycorrhizal relationship. They establish nutrient exchange by penetrating the root cortical cells of the host plant, forming a mutualistic relationship where both the fungus and the plant benefit. The plant provides the fungus with sugars and lipids formed through photosynthesis, while the fungus supplies the plant with water and minerals such as phosphorus, zinc, and copper. This relationship is crucial for the plant's nutrition and growth, especially in soil with limited nutrients.
Ectomycorrhizae, on the other hand, developed much later during the Jurassic period. They form a thick mantle of hyphae surrounding the root and extend into the spaces between the cortical cells. Ectomycorrhizal fungi are more advanced and are commonly found in woody and tree species. They play an important role in the absorption of phosphate, ammonium, and zinc from the soil.
The evolution of mycorrhizal fungi has been crucial in the colonization of terrestrial plants. Mycorrhizal fungi served as a primitive root system for early terrestrial plants, allowing them to access nutrients from the soil. The thin hyphae of the mycorrhizal fungus increase the root surface area for absorption, enabling the plant to acquire nutrients that would otherwise be unavailable. This relationship has benefited the survival and growth of both the fungus and the host plant.
In summary, mycorrhizal fungi are ancient and have played a significant role in the evolution and survival of terrestrial plants. The development of mycorrhizal relationships allowed plants to access essential nutrients from the soil and adapt to life on land. Arbuscular and ectomycorrhizal relationships, in particular, have had a profound impact on the evolution and diversity of plant life on Earth.
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Mycorrhizae are crucial in gathering phosphorus
Mycorrhizae are symbiotic associations between fungi and plants, with the former colonizing the latter's root tissues. The name is derived from the Ancient Greek 'mukēs' (meaning fungus) and 'rhiza' (meaning root). Mycorrhizae play a crucial role in plant nutrition, soil biology, and soil chemistry. They are also essential in the uptake of phosphorus by plants.
Phosphorus is crucial for the normal growth and development of plants. While it is often present in the soil in large amounts, its bioavailability is low due to complexation with other elements like iron, calcium, and aluminium. Mycorrhizae, particularly arbuscular mycorrhizal fungi (AMF), can facilitate the uptake of limiting or inaccessible nutrients like phosphorus by plants. They achieve this by increasing the absorptive surface area of the root system. The hyphae of mycorrhizae are thinner than plant roots, allowing them to access more soil volume and extract phosphorus from areas that plant roots cannot reach.
The importance of AMF in phosphorus uptake is evident in a study on Solidago canadensis, an invasive clonal plant. The study found that AMF colonization and spore production were significantly higher in insoluble phosphorus conditions, enhancing above-ground plant growth by almost 50%. Additionally, AMF facilitated phosphorus acquisition by the plant, allowing it to invest less in below-ground biomass.
Mycorrhizae have also been explored for their potential in phytoremediation, particularly in improving water quality by reducing phosphorus pollution. Excess phosphorus in waterways can lead to algal and cyanobacterial blooms, negatively impacting ecosystems, water use, and human and animal health. By facilitating increased phosphorus uptake by plants, mycorrhizae can aid in phosphorus removal from soil and water, mitigating the negative effects of phosphorus pollution.
In conclusion, mycorrhizae play a crucial role in gathering phosphorus for plants, enhancing their growth and development. Their ability to access and uptake phosphorus from the soil makes them valuable tools in agriculture and environmental remediation, particularly in maintaining water quality.
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Mycorrhizal fungi help plants resist drought
Mycorrhizae are symbiotic associations between a fungus and a plant's root system. Fossil and genetic evidence indicates that mycorrhizae are ancient, potentially as old as the terrestrialization of plants. Mycorrhizae play important roles in plant nutrition, soil biology, and soil chemistry. The plant provides the fungus with sugars or lipids, and the fungus supplies the plant with water and minerals.
Mycorrhizae can help plants resist drought in several ways. Firstly, they increase the surface area of the roots, allowing the plant to absorb more water and nutrients from the soil. This is particularly important in arid conditions, where water is scarce. Mycorrhizae also form a network of mycelium external to the tree roots that extends into the soil, further enhancing the plant's ability to absorb water and nutrients.
Additionally, mycorrhizae can improve the plant's water status and soil-plant hydraulic conductance under drought conditions. They can also regulate genes in the MAPK pathway, enhancing the plant's drought resistance. In apple trees, for example, silencing the MdGH3-2/12 gene reduces drought resistance. Mycorrhizae have also been shown to improve plant growth, photosynthesis, antioxidation, and osmosis under drought conditions.
Mycorrhizae are particularly important in arid desert ecosystems, where they form positive symbiotic associations with a considerable percentage of terrestrial plants. They help desert plants develop complex adaptation strategies and resistance mechanisms to ameliorate the abiotic and biotic stresses of extreme desert environments. Mycorrhizae have been observed in the roots of native desert plants, suggesting that they are crucial constituents of root systems in desert habitats.
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Mycorrhizal mushrooms can extend a plant's root system
Mycorrhizae are symbiotic associations between fungi and plants. The term mycorrhiza is derived from the Ancient Greek "múkēs" (fungus) and "rhíza" (root). Mycorrhizae play an important role in plant nutrition, soil biology, and soil chemistry. They are found in the roots of vascular plants, but mycorrhiza-like associations also occur in bryophytes. Fossil and genetic evidence indicates that mycorrhizae are ancient, potentially as old as the terrestrialization of plants.
The two main classes of mycorrhizae are ectomycorrhizae and endomycorrhizae. Ectomycorrhizae, also known as sheathing mycorrhizae, cover the ends of young roots and penetrate the cell wall of the cortex without invading other cells. They are commonly found in evergreen and deciduous trees and shrubs. Ectomycorrhizae absorb phosphate, ammonium, and zinc from the soil. Endomycorrhizae, on the other hand, produce hyphae inside the roots. Arbuscular mycorrhizae, the most common type of endomycorrhizae, form vesicles that facilitate the exchange of water and nutrients between the plant and fungus.
Mycorrhizal relationships are ancient, with arbuscular mycorrhizae potentially evolving alongside terrestrial plants 450-500 million years ago. Fossil evidence suggests that early land plants that lacked roots formed arbuscular mycorrhizal associations. Genetic evidence also indicates that proto-mycorrhizal fungi may have played a crucial role in enabling plant terrestrialization. Today, mycorrhizal fungi benefit 80-90% of all plant species. They are particularly important for wild plants, but less so for cultivated plants that rely on fertilisers.
In summary, mycorrhizal mushrooms can extend a plant's root system by providing a larger absorption area and accessing more nutrients and water from the soil. This symbiotic relationship is beneficial to both the fungus and the plant, and it has played a significant role in the evolution and survival of terrestrial plants.
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Mycorrhizae may have a parasitic association with host plants
Mycorrhizae are symbiotic associations between fungi and plants, with the fungus colonizing the host plant's root tissues. The term 'mycorrhiza' comes from the Ancient Greek 'múkēs' (fungus) and 'rhíza' (root). Mycorrhizae play a crucial role in plant nutrition, soil biology, and soil chemistry. While the association is typically mutualistic, in certain species or circumstances, mycorrhizae may exhibit a parasitic relationship with their host plants.
In a mycorrhizal relationship, the fungus invades the host plant's root system, either intracellularly, as seen in arbuscular mycorrhizal fungi, or extracellularly, as in ectomycorrhizal fungi. This natural infection allows the fungus to obtain sugars or lipids produced by the plant through photosynthesis, while the plant gains access to water and essential nutrients from the fungus. Mycorrhizae increase the surface area of absorption for the plant roots, enhancing their ability to acquire nutrients from the soil.
However, in some cases, mycorrhizae can have a parasitic association with their host plants. For example, certain plants in the subfamily Monotropoideae of the Ericaceae, as well as several genera in the Orchidaceae, exhibit a non-mutualistic, parasitic type of mycorrhizal symbiosis. These plants derive their carbon from the fungus partner, making them heterotrophic or mixotrophic. This parasitic relationship is also observed in ericoid mycorrhizae, where the plants obtain nutrients from decomposing materials through the activities of their fungal companions.
The Orchidaceae family is particularly dependent on mycorrhizae, as the absence of the correct mycorrhizae can be fatal even to germinating seeds. Additionally, every orchid undergoes myco-heterotrophic growth at some point in its life cycle, forming orchid mycorrhizas with various basidiomycete fungi. This parasitic association is characterized by the formation of pelotons (coils) within the root cells, facilitating the exchange of nutrients.
The nature of the mycorrhizal relationship, whether mutualistic or parasitic, depends on the specific species involved and the environmental conditions. Mycorrhizae have evolved multiple modes of exchange between root cells and hyphae, and their associations with plants are ancient, potentially coinciding with the evolution of terrestrial flora.
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Frequently asked questions
Mycorrhizal fungi are those that have a symbiotic relationship with the roots of many plants. They are often referred to as "fungal roots".
The fungi colonize the host plant's root tissues either intracellularly (as in arbuscular mycorrhizal fungi) or extracellularly (as in ectomycorrhizal fungi). The fungi receive food from the plant, and in exchange, the plant receives water and nutrients from the fungi.
Mycorrhizal mushrooms are mutualistic fungi that form symbiotic relationships with plants and trees. They are one of the four groups of mushrooms classified by how they get their nutrition.
Mycorrhizal mushrooms can extend a plant's root system by up to 1000 times, helping the plant resist drought, produce bigger crops and flowers, resist diseases, and thrive on poor soils or adverse conditions.
