Root system is not only for absorption of water and minerals but also to support storage of food and respiration. Roots in some plants change their shape and become modified to perform other functions. Tap roots of carrot, turnips and adventitious roots of sweet potato, get swollen and store food. A banyan tree has hanging structures called stilt roots. In some plants such as Rhizophora growing in swampy areas, many roots come out of the ground and grow vertically upwards. Such roots, called pneumatophores, help to get oxygen for respiration.