In a mycorrhiza, the fungus lives inside the plant roots, and in the earth. The fungal hyphae are more efficient than plant roots at absorbing nutrients.
Mycorrhizas are important for plant growth in many ecosystems. At least 80% of all land plant species (and over 90% of families) have mycorrhiza. They depend on it for survival. They are the most common symbionts in the plant kingdom: they involve about 6000 species of fungi and 240,000 species of plants.
Mycorrhizas are divided onto two main types: ectomycorrhiza and endomycorrhiza. The hyphae of ectomycorrhizal fungi do not penetrate individual cells within the root, while the hyphae of endomycorrhizal fungi penetrate the cell wall and invaginate the cell membrane.
The mycorrhizal symbiosis is ancient, dating to at least 400 million years ago.