A mutually beneficial (mutualistic)
association occurring between plant roots and
a soil fungus. Mycorrhizal roots take up
nutrients more efficiently, and the fungus
benefits by obtaining carbohydrates from the
tree. An ectotrophic mycorrhiza occurs on
many tree species, which usually grow much
better, most noticeably in the seeding stage,
as a result. Typically the roots become
repeatedly branched and coral-like,
penetrated by hyphae of a surrounding fungal
mycelium. In an endotrophic mycorrhiza, the
growth of the fungus is mainly inside the
root, as in orchids. Such plants do not
usually grow properly, and may not even
germinate, unless the appropriate fungus is
present.