💧 Water Potential Calculator
Assess plant water status by summing component potentials (MPa) in laboratory or field measurements.
Typically negative; derived from osmotic potential measurements.
Turgor pressure in plant cells (positive) or tension in xylem (negative).
Usually negligible in small plants; include for tall trees or column height (≈0.01 MPa per meter).
Relevant in soils and tissues with adhesion; usually negative.
How to Use This Calculator
Measure component potentials
Use pressure chambers, thermocouple psychrometers, or soil probes to determine Ψ components.
Enter MPa values
Ensure consistent units (megapascals). Negative values indicate suction or tension.
Interpret totals
More negative total Ψ indicates drier conditions or greater plant water stress.
Formula
Ψw = Ψs + Ψp + Ψg + Ψm
Water moves from higher (less negative) Ψ to lower (more negative) Ψ. Most plant tissues have Ψ between 0 and −3 MPa depending on hydration status.
Full Description
Total water potential integrates osmotic forces, turgor pressure, gravity, and matrix adhesion to describe water movement in plants and soils. Monitoring Ψ helps optimize irrigation and diagnose stress.
Use this tool alongside sap flow sensors or soil moisture probes to maintain target irrigation setpoints in controlled environments.
Frequently Asked Questions
Why are some potentials negative?
Solute and matric potentials are typically negative because they reduce free energy compared with pure water.
Do I always include gravity?
Only when vertical distance is significant (≈0.01 MPa per meter between leaves and roots).
How do I measure Ψ<sub>s</sub>?
Use osmometry or determine solute concentration to calculate osmotic potential (Ψ<sub>s</sub> = −RTC).
What is a typical leaf water potential?
Well-watered leaves often range from −0.3 to −1.0 MPa, while drought-stressed plants can reach −1.5 MPa or lower.