BIOL 1202 Study Guide - Midterm Guide: Active Transport, Digestion, Osmosis
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How this works: higher water potential in soil relative to the root cells, the waterproof casparian strip blocks movement of water between cells at the endodermis, the cell membranes of the endodermis act as a gate separating the outer low mineral (high water) solutions from the inner high mineral (low water) solutions, therefore, water moves from the cells and the extracellular space outside the casparian strip, through the endodermal cells, and into the extracellular space inside the vascular cylinder by osmosis, water moves from the extracellular space of the vascular cylinder into tracheids and vessel elements of xylem through the cell wall pits, water is then pulled up the xylem, powered by evaporation of water from the leaves. Evaporation in the leaves controls the movement of water and minerals up from chain the leaves the roots: the flow of water in xylem is unidirectional because only the shoot has openings in the epidermis where water can escape.
