Conduction of water in plants is less elaborate than that of animal as well as plants. Plants are less active, so their cells do not need quick supply of materials. So, the only substances which are to be supplied to a plant through vascular bundle are water and minerals, this process is called ascent of sap. These materials are not available from air. Transport system also helps to carry food prepared in the leaves to the various parts of the plant like stems , roots etc. Ascent of sap is executed by two types of vascular bundles: Xylem which transports water and Phloem which transports prepared food.