alleryStart learning →What does the Casparian strip force water and dissolved solutes to do?
AMove upward only through the pericycle
BSlip between the cells of the endodermis
CCross the plasma membranes of endodermal cells
DCollect in the pith at the root centre
Answer & Solution
Correct answer: C. Cross the plasma membranes of endodermal cells
1. The endodermis separates the stele from the ground tissue and acts as a checkpoint for materials entering the vascular system.
2. A waxy substance called suberin sits on the walls of the endodermal cells, and this waxy region is the Casparian strip.
3. It forces water and solutes to cross the plasma membranes of endodermal cells rather than slipping between them.
4. Because every molecule must pass through a membrane, only materials the root requires get through.
5. Toxic substances and pathogens are generally excluded by that same checkpoint.
6. Slipping between the cells is precisely the route the strip blocks, so that option states the opposite of the mechanism.
_Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 30 "Plant Form and Physiology", section 30.3 Roots_
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