Examples of storage roots.
Many plants have modified roots. Some of these arise from roots, or parts of roots, and others are adventitious, developing from stems and, in rare cases, leaves.
These specialized roots serve adaptive purposes like providing more support and anchorage, store water and nutrients or absorb oxygen or water from the air.
Prop roots: A root that acts as a prop or support is called prop root. Prop root grows from the lower part of a stem or trunk down to the ground, providing a plant with extra support and serve as food gatherer. Corn and many tropical plants produce prop roots.
Storage roots: These roots are modified for storage of food or water, such as carrots and beets. They include some taproots and tuberous roots. In the case of carrots and parsnips, the storage root is also a tap–root. In dahlias and sweet potatoes, storage roots develop on branch roots. Many biennials––plants that live for two years–spend their first year collecting carbohydrate in their storage roots, then the second year they use their stored carbohydrate to grow fast, maybe overtopping the plants around them that don't have energy stored in the form of carbohydrate.
Buttress roots
Large trees which grow in the wet unstable soils of the rainforest produce massive outgrowths at their base.
Aerial roots A root that develops from a location on a plant above the surface of the earth or water, as from a stem. For example, some orchids have aerial roots that grow from their stems and absorb water directly from the air. Aerial roots anchor climbing stems to vertical surfaces. Aerial roots are almost always adventitious (Organs arising where they are not typically found, such as these roots arising from along a stem, are said to be adventitious). One of the more spectacular examples is the banyan tree, which has roots, which grow down from the branches and take root in the soil. The mangrove tree and some orchids also have aerial roots. Also some vines grow aerial roots like the trumpet vine and Ceriman.
Buttress roots Large trees which grow in the wet unstable soils of the rainforest produce massive outgrowths at their base. These are essential in these wet unstable soils. Pneumatophores are specialized aerial roots enable plants to breathe air in habitats that have waterlogged soil. These "breathing roots" have special air channels (lenticels) for gas exchange in the atmosphere (air enters at zones called "pneumathodes") and there is an internal pathway for getting O2 into the root and to supply submerged roots.