Term:

Mycorrhiza (plural = mycorrhizae)
Definition:

A mutualistic symbiotic relationship between certain fungi and the roots of many species of vascular plants. Both the fungus and the vascular plant benefit---the fungus receives carbohydrates from the plant and the plant receives receives mineral nutrients from the fungus. In order to facilitate the transfer of carbohydrate and minerals the hyphae of the fungus penetrate the roots of the vascular plant hosts.