In botany, the radicle is the first part of a seedling (a growing plant embryo ) to emerge from the seed during the process of germination. The radicle is the embryonic root of the plant, and grows downward in the soil (the shoot emerges from the plumule ). Above the radicle is the embryonic stem or hypocotyl , supporting the [LINK|lang_en|Cotyledon|cotyledon].
A radiole is a heavily ciliated feather-like tentacle found in highly organized clusters on the crowns of Canalipalpata. Canalipalpata is an order of sessile marine polychaete worms consisting of 31 families (including the Sabellidae, Serpulidae, Terebellidae, and Alvinellidae, a family of deep-sea worms associated with hydrothermal vents). These benthic annelid tube worms employ radioles primarily for alimentation. While their primary role is to function as an organ for filter feeding, radioles also serve as respiratory organs. Because of their role in gas exchange, radioles are often referred to as "gills ".