The plasmalemma and the tonoplast in an osmotic system function as

The plasmalemma and the tonoplast in an osmotic system function as Correct Answer Semipermeable membrane

The plasmalemma and the tonoplast in an osmotic system function as Semipermeable membranes.
Plasmalemma is selectively permeable because substances do not cross it indiscriminately. The main function of a semipermeable membrane in cells is to separate the cell from the environment while allowing for the controlled transport of molecules in and out of the cell.
Tonoplast is a single membrane that bounds the vacuoles and separates them from the cytoplasm. The vacuoles release their contents into the cytoplasm, diluting the cytoplasm and restoring the osmotic balance across the cell membrane.