Saprotrophic fungi absorb nutrients from decaying organic matter. They release acids and enzymes that break dead tissue down into smaller particles so it can be absorbed. These mushrooms are extremely important to the food chain because they help recycle dead matter back into the soil.
Saprotrophic behavior is one of the four ways fungi obtain nutrients. Myorrhizal mushrooms form symbiotic relationships with other plants and animals. Usually, the relationship is mutualistic, meaning both organisms benefit. The mushroom weaves around the root cells of the plant or wraps around the roots themselves. The mushroom provides additional moisture and nutrients to the plant, and in turn, it gains access to sugars the plant produces. Endophytic fungi also form a mutualistic relationship with a host plant. However, they have their own category because, unlike myorrhizal mushrooms, they can easily be cultivated in a lab without a host plant present. Parasitic mushrooms infect and feed on living organisms, eventually killing them.