Plants obtain water and many essential nutrients through their roots. Small extensions from root cells called root hairs greatly increase the surface area across which absorption occurs. The water and dissolved nutrients enter vessels called xylem through which they can move upward through the stem to the leaves. Another type of vessel lies next to xylem. This is phloem, which transports sugars from places of production or storage to tissues that require them. Phloem also transports amino acids and hormones.