Records were made of whether the droplets sank, rose or remained suspended in the solution. Suspension means the leaf tissue is isosmotic with the 20 ml test tube solutions. If the droplet sank, the leaf had a lower water potential than the solution, and if it rose it had a higher water potential. Water potential was calculated by using the calculation formula of water potential ( w = −iRTC). In this formula, i is dissociate coefficient, and sucrose is 1; R is gas constant, 0.083 L bar mol−1 K−1; T is absolute temperature (to wit: 273 ◦C + t, t is the temperature in experiment); C is the concentration of isotonic solution, mol/L