Final answer:
The selective uptake of water and minerals in a root involves a combination of osmosis, active transport, and passive diffusion, with the endodermis acting as a selective barrier.
Step-by-step explanation:
The selective uptake of water and minerals in a root takes place through a combination of processes including active transport and passive diffusion. The roots absorb water primarily through osmosis, where water moves from an area of higher water potential to areas of lower water potential within the plant. In the case of mineral ions, these are often taken up by root hair cells through active transport, where cellular energy is used to move minerals against their concentration gradient.
The endodermis acts as a selective barrier in this process, ensuring that only certain substances are allowed to enter the plant's vascular system. Passive diffusion also plays a role, especially when the concentration of minerals outside the roots is higher than inside, allowing for their natural diffusion into the roots.