A mycorrhiza is a special organ. Mycorrhiza singular, mycorrhizae plural. Mycorrhizae are nonwoody structures that are composed of root and fungus tissue. The organ is not a fungus and it is not a root, it is BOTH. The word mycorrhiza is Greek for fungus root.
There are basic types of mycorrhizae, the ectomycorrhizae which have their fruiting bodies above the ground, and the endomycorrhizae which have the fungus tissue within the soil inside the roots and cells. Thus, oaks, beeches and pines, amongst others, which need the ecto-variety can be killed by soil compaction. Conversely, trees like the maples, ash, elms and sycamores can survive under a blacktop because their endomycorrhiza does its fruiting underneath. But it should be stressed that under any circumstances soil compaction may be hazardous to a tree's health. As always, in nature there are varieties between these two. In this connection let's remember not to plant grass near trees because mycorrhizae flourish in leaf compost while grass does the opposite.
As a nonwoody root begins to develop from a woody root [A], a fungus can infect the root [B], then a great variety of branching and swollen structures (organs) can result [C] on the nonwoody roots. Mycorrhizae can last a few weeks to a year. And as old ones die, new ones begin.
The mycorrhizae have a membrane on the tip that can facilitate the absorptions of elements, i.e., especially phosphorus (P), zinc (Zn), manganese (Mn), copper (Cu) and also water. Remember, mycorrhizae form near the surface of the soil where leaves and twigs have decomposed, e.g., in the forest. It is time to define some of the words we use. A FOREST is a SYSTEM where trees and many other communities, of living things, are all connected in a way that insures survival for ALL! A forest is very much like a spider web, i.e., we cannot touch any one part without affecting the rest of the web.
Mycorrhizae can be found in abundance at many trees, e.g., beeches, in the leaf mulch (last years fallen leaves). COMPACTION of the LIVING SOIL destroys the habitat for the mycorrhizae leading to many problems.
Diagrams from The Desk of John A. KESLICK Jr.
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John A. Keslick Jr.
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