noun, plural: aerial roots
A type of root that grows from the stem above the ground
Aerial root is a type of root wherein it grows from the stem of the plant, i.e. above the ground. This type of root absorbs water directly from the air. This is exemplified by the roots of the epiphytes (e.g. orchids). Aerial roots are adventitious roots. Other plants with aerial roots include those of the tropical coastal swamp trees, e.g. mangroves, banyan trees, Metrosideros robusta (rātā) and M. excelsa (pōhutukawa), and certain vines such as Hedera helix (Common Ivy) and Toxicodendron radicans (poison ivy).
Most plants have roots growing at the bottom or basal of a plant body. When roots grow above the ground and elsewhere of the plant body they are referred to as adventitious roots. Aerial roots are an example of adventitious roots. There are different types of aerial roots. These are stranglers' roots, pneumatophores, haustorial roots, and propagative roots. The roots of strangler plants are those in which the aerial roots eventually strangle the plant of which they grow, e.g. Ficus sp. Pneumatophores are aerial roots specialized for gaseous exchange, e.g. roots of mangrove tree. Haustorial roots are those found in parasitic plants, e.g. roots of mistletoe. Propagative roots are those that develop from the plant nodes such as those found in strawberry runners and sider plants.