Ectomycorrhiza

Ectomycorrhiza

Ectomycorrhiza is a mutualistic symbiotic association between certain fungi and the roots of plants, particularly trees. This type of mycorrhiza is characterized by the formation of a dense network of fungal hyphae that surround and penetrate the root cells, forming a sheath-like structure known as the mantle. The fungal hyphae extend into the surrounding soil, effectively increasing the surface area available for nutrient absorption by the plant.

Ectomycorrhiza symbiosis between a fungus and a tree root

Formation and Function

The formation of ectomycorrhiza begins when fungal spores or mycelium come into contact with the roots of a compatible host plant. The fungus then colonizes the root surface and forms a mutualistic relationship with the plant. The fungal hyphae grow between the root cells, forming a dense network that provides several benefits to both the fungus and the plant.

One of the key functions of ectomycorrhiza is nutrient exchange. The fungal hyphae have a much larger surface area compared to the plant roots, allowing for increased absorption of nutrients, particularly phosphorus and nitrogen, from the soil. In return, the fungus provides the plant with essential nutrients, such as carbon compounds, that it obtains through the decomposition of organic matter in the soil.

Another important function of ectomycorrhiza is protection against pathogens and environmental stresses. The fungal mantle acts as a physical barrier, preventing the entry of harmful microorganisms into the root system. Additionally, the fungus produces various bioactive compounds that can inhibit the growth of pathogenic organisms. Furthermore, the presence of ectomycorrhiza has been shown to enhance the plant's tolerance to drought, salinity, and heavy metal toxicity.

Importance and Distribution

Ectomycorrhiza is of great ecological and economic importance. It is estimated that around 5-10% of all plant species form ectomycorrhizal associations, including many economically valuable trees such as pines, oaks, and birches. These associations play a crucial role in forest ecosystems by promoting nutrient cycling, enhancing tree growth, and improving soil structure.

Global distribution of ectomycorrhizal plants

The distribution of ectomycorrhizal plants is not uniform across different ecosystems. They are particularly abundant in temperate and boreal forests, where they form mutualistic associations with a wide range of tree species. In contrast, tropical forests are dominated by arbuscular mycorrhizal associations, which involve a different group of fungi.

Conservation and Management

The conservation and management of ectomycorrhizal associations are of increasing interest, especially in the context of sustainable forestry and ecosystem restoration. The removal of trees from forests can disrupt the delicate balance of ectomycorrhizal communities, leading to negative impacts on tree regeneration and overall ecosystem functioning.

See Also

• Mycorrhiza
• Arbuscular mycorrhiza
• Mycorrhizal fungi
• Mycorrhizal networks
• Symbiosis
• Plant-microbe interactions