An isotonic solution is when there concentration of solutes in the cell are equal on the inside and the outside of the membranes. So, you would not observe any noticeable change. In a hypertonic solution, the solutes on the outside of the cell are greater than on the inside. You would observe the cell becoming smaller as it loses water. Hypotonic has just the opposite problem: the solutes outside of the cell are less than the solutes within the cell...making it look swollen. You could even observe that the cell has ruptured.
