Mycorrhiza facts for kids

A mycorrhiza (say it: my-koh-RY-zuh) is a special partnership between a fungus and the roots of a plant. The word "mycorrhiza" comes from Greek words meaning "fungus roots."

In this partnership, the fungus lives both inside the plant roots and in the soil around them. The tiny threads of the fungus, called hyphae (say it: HY-fee), are much better than plant roots at soaking up important nutrients from the soil.

Mycorrhizas are super important for plants to grow well in many different ecosystems. Did you know that at least 80% of all land plant species (and over 90% of plant families) have mycorrhizas? Many plants actually depend on this partnership to survive! It's one of the most common partnerships in the plant world, involving about 6,000 types of fungi and 240,000 types of plants.

Mycorrhizas are split into two main kinds: ectomycorrhiza and endomycorrhiza.

• In ectomycorrhiza, the fungus threads (hyphae) grow around the plant root cells but don't go inside them.
• In endomycorrhiza, the fungus threads actually push into the plant cell walls and touch the cell membrane inside.

This amazing partnership has been around for a very long time, at least 400 million years!

How This Partnership Works

This helpful partnership is a mutualism, meaning both the fungus and the plant benefit. The plant gives the fungus sugars, like glucose, which the plant makes using sunlight through photosynthesis. These sugars travel from the plant's leaves down to its roots and then to its fungal partner.

In return, the plant gets help from the fungus's huge network of threads, called a mycelium (say it: my-SEE-lee-um). This mycelium acts like a giant sponge, soaking up water and important mineral nutrients from the soil, especially phosphorus.

The fungus is great at absorbing nutrients because its threads are much thinner than even the smallest plant root. This means they can spread out and explore a much larger area of soil. Scientists estimate that just one kilogram (about 2.2 pounds) of soil can contain at least 200 kilometers (about 124 miles) of fungal threads!

Big Advantages for Plants

Plants that have mycorrhizas often have many benefits:

• They are more resistant to diseases caused by tiny germs in the soil.
• They can handle drought (very dry periods) better.

These advantages probably come from the improved way mycorrhizal plants take in water and minerals.

Mycorrhiza is especially helpful for plants growing in soil that doesn't have many nutrients. If you try to grow plants in sterile soil (soil with no fungi), they often don't do well unless you add mycorrhizal fungi. Without these fungi, plants might grow very slowly in tough environments.

Sometimes, the fungal partners can even help transfer sugars and other nutrients from one plant to another! These connected plant and fungus communities are called common mycorrhizal networks.

Some fungi also live inside the roots, stems, and leaves of plants without causing disease. These are called endophytes. Like mycorrhizas, endophytes can benefit both the fungus and the plant. For example, endophytes in grasses can make the grass more resistant to animals that try to eat it, and in return, the fungus gets food and shelter from the plant.

Fungi and Tiny Bacteria

Mycorrhizal roots are also great places for other tiny living things, called microbes, to live. Some mycorrhizal fungi can even host bacteria inside their own cells! One well-known example is a fungus called Geosiphon pyriforme, which can host cyanobacteria (a type of bacteria that can do photosynthesis) inside special balloon-like parts.

Even more interesting, a type of mycorrhiza called Arbuscular Mycorrhiza (AM) fungi are unique because they can host bacteria right in their cytoplasm (the jelly-like stuff inside cells). Scientists first saw structures that looked like bacteria inside these fungi in the 1970s, and later research confirmed they were indeed real bacteria.

Images for kids

• 

  The Leccinum aurantiacum mushroom, which is an ectomycorrhizal fungus.

• 

  An ericoid mycorrhizal fungus that was found on the Woollsia pungens plant.

See also

In Spanish: Micorriza para niños