Final answer:
The Casparian strip, located in the endodermis, is responsible for the selective uptake of minerals in the root. It forms a critical checkpoint by filtering water and minerals before they enter the plant's vascular system.
Step-by-step explanation:
The Casparian strip is responsible for the selective uptake of minerals in the root. Located in the endodermis, the Casparian strip is a waxy barrier composed of suberin that ensures water and solutes cross the plasma membranes of endodermal cells. This mechanism allows the plant to regulate the movement of water and dissolve nutrients, ensuring only necessary materials pass into the root's vascular system and ultimately reach the stele. As it forces substances to move through the symplast, rather than the apoplast, it effectively filters them before they enter the vascular tissue.
The function of the Casparian strip in relation to the selective uptake of minerals highlights its significance. By entering the symplast at the endodermis, water, and minerals are filtered through the cell membranes, allowing the plant to control the internal environment and exclude toxic substances and pathogens. The endodermis and the Casparian strip thus establish a critical checkpoint for sustenance and protection of the plant.