In some cases the shape of the root, and also its function, differ from the common type just described.
There are in fact some roots, called aerial roots which have a large surface, but are devoid of absorbent hairs.
They never reach the ground and therefore absorb moisture from the atmosphere.
Roots of this type develop only in warm-humid environments such as, for example, the equatorial forest (eg epiphytic orchids).
There are also roots that descend from the branches of the trees to the ground and perform a support function towards them: they are called columnar roots (eg Ficus europea).
Some plants, typical of marshy soils, have particular roots which, coming out of the ground, grow upwards; they are called respiratory roots because their function is to provide oxygen for the respiration of the partially submerged plant (eg Taxodium). In the roots of aquatic plants, the lack of root hairs is noted, since all the immersed parts can perform the absorption function.