The water-repellent Casparian strip forces water to move through the cytoplasm of the cells of the endodermis. Therefore, membrane transport proteins help control the types of absorbed solutes that will become distributed throughout the plant. Most flowering plants also have an exodermis, a layer of cells just inside the roots which also has a Casparian strip that functions just like the one next to the root vascular cylinder. Water Transport Transpiration Water moves from roots to stems and then to leaves. Water moves through pipelines called xylem.
Some water is used for growth and metabolism, but most evaporates into the air by transpiration.
Transpiration puts the water in the xylem in a state of tension leading from leaves to stems to roots. As long as water molecules escape from the plant, molecules are pulled up to replace them. Columns of water are pulled upward, aided by the hydrogen bonds between water molecules that are confined to the tubular xylem cells. Hydrogen bonds are strong enough to hold water molecules together in the xylem but not strong enough to prevent separation during transpiration. The cuticle is a translucent, water-impermeable layer secreted from epidermal cells.