noun, plural: advemtitious roots
A root growing on the stem, leaf, or other body parts apart from the usual the basal root system of the plant, particularly the radicle or root branches
Typically, the roots grow from any part of the basal root system of the plant, which are located underground. However, there are roots that grow from various parts of the plant body apart from the radicle or the branches of the roots. These roots are called adventitious roots. They may grow from the stems, leaves, nodes, internodes, etc. of the plant. The formation of adventitious roots increases the success rates of vegetative propagation of certain plants.
Adventitious roots may be aerial or underground. An aerial root grows above the ground and absorbs nourishment directly from the air. This is exemplified by the roots of the epiphytes (e.g. orchids), the strangler roots of banyan trees, the pneumatophores of the mangroves, the haustorial roots of the mistletoe plant, and nodal roots of strawberry runners and sider plants. Underground adventitious roots are exemplified by the fibrous roots that grow from the nodes of a horizontal stem and are specifically referred to as surface feeders as they remain near the soil surface and do not penetrate the soil deeply.1
1 Manisha, M. (n.d.). Adventitious Root System: Definition and Types. Retrieved from http://www.biologydiscussion.com/root/adventitious-root-system-definition-and-types-plants/70049.