Two of the most important things that a plant needs to survive are food and water. These two things need to be transported to different parts of the plant. For example, the leaves need water, but the water comes through from the roots, and the roots need food, but the food comes from the leaves.                                       

Plants have developed a network transport vessels to transport these substances around the plant. The plant uses xylem to transport water and phloem to transport food (sugars).