Final answer:
Root hair cells require active transport to absorb minerals because mineral ions can't freely diffuse through the cell's hydrophobic membrane.
Step-by-step explanation:
Root hair cells can't use diffusion to take in minerals from the soil primarily because mineral ions carry a charge and are not able to freely cross the hydrophobic lipid bilayer of the root hair cell membrane.
Instead, these minerals require active transport, where the plant expends energy to absorb nutrients against their concentration gradient.
The root epidermis is an outer layer of cells designed for protection and absorption, with root hairs increasing the surface area for water and minerals.
When in contact with soil, minerals dissolved in water are taken up first by the hydrophilic walls of root hairs and then need to be actively transported into the cell.
Due to the nonpolar nature of the cell membrane, ions and charged particles cannot diffuse freely through it, necessitating energy-driven mechanisms to move these essential nutrients into the plant's vascular tissue for distribution.