AP BIOLOGY

Detailed explanation-1: -In the apoplast pathway, water is transported from root hair to xylem through the cell wall of intervening cells. Apoplastic water movement beyond the cortex is blocked by the Casparian strip of endodermal cells. Hence, the symplastic route is utilised to deliver water and ions beyond the cortex.

Detailed explanation-2: -The root, therefore, has something called the Casparian strip which is a waxy strip within the cell walls which is impermeable to water. This forces the water to go through a cell membrane which can then control which substances are allowed to enter the plant.

Detailed explanation-3: -The Casparian strip acts as a water-impermeable material that binds to the plasma membrane of the endodermal cells.

Detailed explanation-4: -The casparian strip does not allow the water to penetrate it as the suberin is impermeable to water. As a result the water moves through the symplastic pathway that is through the plasmodesmata of the cells to reach the cells of the xylem.