Plants absorb minerals from the soil through both passive and active transport. In passive transport, the ions just pass through the cell membrane of the root cells by osmosis or diffusion. On the other hand, active transport takes place when the ions move against the concentration gradient with the expense of energy to cross the cell membrane.
The endodermal cells of the root have many transport proteins embedded in their plasma membrane. These transport proteins serve as control points, where they adjust the quantity and selectively allow the types of solutes to cross the membrane to reach the xylem. The suberin layer of the casparian strip enables the root epidermis to transport ions passively in one direction only.
The active transport of ions causes a water potential gradient in the roots, which results in the uptake of water by osmosis. Once the ions reach the xylem either passively or by active absorption, they are transported up the stem to the various sinks inside the plant body by transpirational pull. These mineral ions are unloaded at the fine vein endings of leaves through diffusion and are taken up for active transport by mesophyll cells.