What is the isotonic value for?
The isotonic value will tell you when the water potential of the potato and that of the solution are equal and opposite, meaning there is no net movement of water through osmosis. water potential is a combination of pressure potential and solute potential. The water potential of pure water is 0. Solutes will make the water potential negative, but pressure or tension can alter the water potential value. Water diffuses from a greater water potential value to a lesser value.
