Mycorrhizae are fungi that are connected to a plant via haustoria. The fungi gain some nutrients from the parent plant, and they benefit the parent plant by absorbing nutrients more efficiently. Some plants, such as rhododendrons and native orchids, are dependent on the mycorrhizae and will not grow without them. Roots found on plants in swampy areas in which there is not enough oxygen in the water for the root to survive. These roots grow toward the water surface and then bend over, forming a knob above the water.
Pneumatophores are almost hollow, allowing air to pass to the living tissue of the root.
A root that acts as support for the parent plant. Most absorption of water and nutrients occurs via root hairs. The carrot is a typical tap-rooted plant.