Every molecule or particle which enters into a cell, it must pass through several cellular structure at different level means it also depends on the type of molecule like size, shape, and nature (characteristics). On the surface of root cell, potassium ion pass through the primary cell wall which is most outer layer of plant cell, then it passes the second layer called plasma membrane, in the plasma membrane cytoplasm is present and when potassium ion reaches the cytoplasm then it will enter into the vacuole present in cytoplasm.
Structurally from the soil into the roots, the structure of the root cells is such a way that k+ enters with water through the primary cell wall → plasma membrane → cytoplasm → vacuole of the root hairs, and move through apoplastic and sympathic pathways from the root hairs .
From the root hairs they moved in mass flow in the xylem vessels. They reentered apoplastic and sympathic pathways again to reach different parts of the plants.
Due to the facts that K+ in the roots cells are of lower water potential,soil water K+ can also move by active transport and facilitated diffusion from the soil into the (primary cell wall → plasma membrane → cytoplasm → vacuole roots,) and later switch to apoplastic and sympathic pathways to reach plant parts.
