[Campbell Biology P.842] What is the primary function of the Casparian strip in the endoderm... | Practice Question

What is the primary function of the Casparian strip in the endodermis, as described in the provided text?

  • A: To facilitate bulk flow of water and minerals directly into the xylem.
  • B: To prevent the apoplastic movement of water and minerals into the vascular cylinder, forcing them through the symplast or across plasma membranes.
  • C: To actively pump mineral ions into the vascular cylinder, creating root pressure.
  • D: To regulate gas exchange between the root and the soil.

Explanation

According to point 4, 'The endodermis: controlled entry to the vascular cylinder stele . Within the transverse and radial walls of each endodermal cell is the Casparian strip, a belt of waxy material purple band that blocks the passage of water and dissolved minerals. Only minerals already in the symplast or entering that pathway by crossing the plasma membrane of an endodermal cell can detour around the Casparian strip and pass into the vascular cylinder stele .' This clearly indicates its role in regulating entry by blocking the apoplastic pathway.