What is the X in X-mas?
The symbiotic association of the mycelium of a fungus with the roots of plants. The majority of vascular plants have mycorrhizae. The fungus assists in the absorption of minerals and water from the soil and defends the roots from other fungi and nematodes, while the plant provides carbohydrates to the fungus. There are two kinds of mycorrhizae: endomycorrhizae, in which the fungal hyphae enter the cells of the root cortex, and ectomycorrhizae, in which they surround the cells.