Answer:
ensures that all water and dissolved substances must pass through a cell membrane before entering the stele.
Explanation:
Casparian strips are the band of waterproof material suberin around the radial and transverse walls of the endodermis of root cells. Till endodermis, the water, and dissolved minerals move through apoplast only. The apoplast includes the movement of water and minerals through the network of interconnected cell walls of adjacent cells.
However, the presence of Casparian strips in endodermis makes water and minerals to enter the cytoplasm from the cell walls through cell membranes. Therefore, water and dissolved minerals move through symplasm via endodermis. Symplasm includes the movement of substances through plasmodesmata, which are the cytoplasmic channels connect the neighboring plant cells.