Calculate total water potential from solute concentration, temperature, and pressure potential.
| Water potential (MPa) | – |
Use this calculator for a plant-physiology or soil sketch of which way water will move. More negative water potential (ψ) means a stronger pull. Here total ψ is solute potential plus pressure potential, for an ideal non-dissociating solute (van 't Hoff, i = 1).
Solute potential is −c R T, with R = 0.008314 L·MPa/(mol·K), c in mol/L, and T in kelvin. Pressure potential is the megapascals you type. Total ψ is the sum, in megapascals (MPa). Temperature can be entered in Celsius (°C) or Fahrenheit (°F); the value is converted to Celsius and then to kelvin inside the formula. Solute concentration stays in mol/L and pressure in MPa; those units are not converted by the unit selector.
This ignores matric potential, gravity, and ion dissociation (for salts, multiply concentration by the van 't Hoff factor i yourself before entering). Atmospheric pressure is about 0.1 MPa; turgid cells are often 0.5–1 MPa.
Solute concentration (mol/L): Osmolarity of a non-dissociating solute, in moles per litre.
Temperature: Temperature used for the gas-law term. Enter the value in °C or °F. The default is 20 °C.
Pressure potential (MPa): Turgor or applied pressure in megapascals.
Water potential (MPa): Total ψ = ψs + ψp, in megapascals.
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