Question 1

1. How do I calculate water potential?

Accepted Answer

Use the formula Ψ = Ψs + Ψp, where Ψs is solute potential and Ψp is pressure potential. Solute potential is found with Ψs = −iCRT, so just add both values together to get the total.

Question 2

2. What is water potential measured by?

Accepted Answer

Water potential is measured with an instrument called a psychrometer, which detects tiny changes in humidity around a sample. In labs, it's also commonly estimated using the Chardakov method with solutions of different concentrations.

Question 3

3. What is the maximum water potential?

Accepted Answer

The maximum water potential is 0, which is the value for pure water at standard atmospheric pressure. Every solution has a lower (more negative) value than this because solutes always reduce it.

Question 4

4. What is water potential?

Accepted Answer

Water potential is the measure of the free energy of water and its tendency to move from one area to another. Water always flows from a region of higher water potential to a region of lower water potential.

Question 5

5. What is the unit of water potential?

Accepted Answer

Water potential is measured in megapascals (MPa), though bars and kilopascals (kPa) are also used sometimes. Since it describes pressure energy, it shares the same units as pressure.

Question 6

6. Is 0 a high water potential?

Accepted Answer

Yes, 0 is the highest possible water potential, because it represents pure water with no solutes or pressure restrictions. Any added solute or tension makes the value negative, which means lower water potential.

Plant Science

Water Potential Calculator Calculate Total Water Potential