Beneath the epidermis of the plant's root is a layer called the cortex, which is made up of layers of cells called vascular rays. The vascular rays carry water through the root and into the stele, the center of the root. Inside the stele are veins that serve as the circulatory system of the plant. Here is where the water begins its journey upward and into the plant.
Water is transported from the roots, where the main portion of water is absorbed, and up the plant through the xylem; the xylem is an interconnected system of tubes where the water circulates through the plant. Water then flows through the cortex of the plant, through the endodermis, or innermost layer of cells, and finally into the cells' vascular bundles. Transpiration, which is the evaporation of water through the stomata, is responsible for the movement of the water from the xylem into the mesophyll cells and finally into the leaves.
Water carries out many important roles for plants. The number one function is hydrating the plant so it's nourished to grow and thrive. Water also regulates the temperature of the plant by drawing more water from the soil and into the leaves and stems of the plant. Water also helps the plant to undergo photosynthesis, where it dissolves the sugars produced in the leaves and carries this solution downward to the roots. As it is travelling down, it feeds every part of the plant.