The outside wall of the cell becomes distended to form a tubular outgrowth which makes contact with the soil and absorbs water and dissolved minerals from it. Water and soluble nutrients enter the root hairs, pass into the rootlets, and travel through the main root into the stems and leaves. Root hairs are formed in great numbers near the tips of roots. In most plants they are short-lived. If a plant is transplanted carelessly, it is the loss of many of these small root hairs with their water-absorbing cells that will cause the plant to wilt.
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.