fungi mushrooms mycology the fifth kingdom

How do fungi form partnerships
with most plants?

How do fungi form partnerships with most plants?

Without fungi, there would be no forests, and perhaps not even any land plants. This is because a few thousand fungi have evolved intimate and essential relationships with the roots of almost all living plants. They work like this...

The fungus explores the soil and brings back scarce mineral nutrients, especially phosphorus, to the plant. The plant hands over to the fungus some of the sugars it has made by photosynthesis.

The fungi grow around and into the roots, establishing a microscopic interface across which phosphorus moves one way while sugars move the other way. Both partners benefit, and neither would thrive without the other.

The partnership is called a mycorrhizal symbiosis, and about 90% of all plants have these specialized fungi on and in their roots.

There are basically 2 kinds of mycorrhiza.

1) The kind established with about 2 000 species of coniferous trees involves about 5 000 fungi of the kind that form mushrooms or truffles. These fungi produce a mantle around the roots and grow between the root cells but never penetrate them. This creates an ectomycorrhiza.

2) The other kind is called an endomycorrhiza. This is a very ancient relationship (it evolved 400 million years ago) and involves microscopic fungi that penetrate the root cells and make tiny tree-like organs inside. These fungi form spores in the soil but no structures that could be seen by the naked eye. Endomycorrhizas are formed by perhaps 250 000 species of plants.

For pictures of both kinds look at Chapter 17. Much more detailed accounts can be found in the book The Fifth Kingdom

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