A band of suberin, an impermeable substance, found in the endodermal cell walls of plant roots; it was named after R. Caspary. Movement of water through the apoplast pathway is diverted from the cell wall to the cytoplasm, where it then follows the symplast pathway. The endodermal cells actively secrete salts into the vascular tissue. This results in a low (more negative) water potential, allowing water to move down a water potential gradient from the endodermis into the vascular tissue. The Casparian strip prevents water and solutes from returning to the cortex; consequently a positive hydrostatic pressure is established in the vascular tissue—the phenomenon of root pressure. It also blocks the entry of potentially toxic substances into the vascular system.