Tap roots are prominent primary roots from which all other lateral rootlets or secondary roots grow. They may divide, become fleshy, and often penetrate deeply into the soil. Fibrous roots are adventitious, have no distinguishable primary root and are composed of a number of fine, thread-like roots of the same kind and size originating at the base of the stem. Fibrous roots often spread out near the surface of the soil, rather than penetrating straight down or deep. Fleshy roots become food reservoirs which retain surplus food during the winter or adverse periods to be used by the plant when it is able to renew its growth.
Aerial roots form freely on many land and water plants in a favorable, moist atmosphere.
These roots enable climbers such as Philodendron spp. The aerial roots of air plants or epiphytes such as some orchids not only attach the plant to its host but also absorb water from the air. Many aerial roots are fleshy or semi-fleshy, functioning as reservoirs for water storage. As the water or ground cuts off the air from the roots, these trees develop woody-knees which protrude above the surface to enable the plant to obtain air. All Rights Reserved.