bsorption selective. The soil solution is usually very dilute, and the roots can accumulate essential minerals to concentrations of these minerals in soil.
             The endodermis is the innermost layer of the cells in the root cortex that surrounds the stele and functions as a last checkpoint for the selective passage of minerals from the cortex into the vascular tissue. Minerals already in the symplast when they reach the endodermis continue right through the plasmodesmata of the endodermal cells and pass through into stele. In the wall of each endodermal cell is a belt made of suberin, a waxy material that is impervious to water and dissolved minerals called the Casparian strip. Because of this Casparian strip water and minerals cannot cross the endodermis and enter vascular tissue via the apoplast. The Casparian Strip also prevents the backflow of water and minerals from the stele back into the cortex.
             The next step in the pathway is the xylem pathway. The xylem pathway is the passage of water and minerals that reach the stele into the tracheids and vessel elements of the xylem. These water-conducting cells lack protoplasts, and thus the lumen of the cells are part of the apoplast. The entry of water and minerals into the xylem requires their transfer from the symplast to the apoplast. Endodermal cells and parenchyma sells within the stele discharge minerals into their own walls. The water and minerals enter the tracheids and xylem vessels. The water and mineral nutrients we have tracked from the soil to the xylem are transported to the shoot system.
             The xylem is important in defying gravity and getting water to the leave. Unless the transpired water is replaced by water transported up from the roots of the xylem, leaves will eventually wilt and die. As water flows in it generates a positive pressure that forces the fluid up the xylem. The cohesion of water due to hydrogen bonding transmits the upward pull along the entire length...