The symbiotic association between fungi and plant roots is called a mycorrhiza. The word combines Greek roots meaning “fungus” and “root,” reflecting the intimate partnership between fungal hyphae and plant root systems.
The fungus extends through soil as a network of fine hyphae, greatly increasing the plant’s effective absorbing area. It can help the plant obtain water and minerals such as phosphorus, nitrogen, and zinc. In exchange, the plant supplies the fungus with photosynthetic products, including sugars and sometimes lipids.
Mycorrhizae are widespread: roughly 80% of studied plant species form these associations, and arbuscular mycorrhizae occur in about 70% of plant species. Ectomycorrhizae form a sheath and Hartig net around root cells, while arbuscular mycorrhizae create tree-shaped structures inside root cells.
A common mix-up is lichen, which is also a fungus-based symbiosis but involves a fungus and a photosynthetic alga or cyanobacterium, not primarily plant roots. The term mycorrhiza was coined by German botanist Albert Bernhard Frank in 1885.