1. What Is Water Potential?

Water potential (Ψ) is the potential energy of water per unit volume relative to pure water in reference conditions. It measures the tendency of water to move from one area to another due to osmosis, gravity, mechanical pressure, or matrix effects.

2. Components of Water Potential

The total water potential is the sum of its components:

Where:

• \( \Psi_s \) — Solute potential (osmotic potential, always negative)
• \( \Psi_p \) — Pressure potential (positive in turgid cells, negative in xylem)
• \( \Psi_m \) — Matric potential (due to surface adhesion, important in soils)
• \( \Psi_g \) — Gravitational potential (depends on height)

Explanation: Each component contributes to the overall water potential, determining water movement in plants and soils.

3. Importance of Water Potential

Details: Water potential is crucial for understanding water movement in plant-soil systems, predicting drought stress, and managing irrigation in agriculture.

4. Using the Calculator

Tips: Enter all components in MPa (megapascals). For negative values, use a minus sign. The calculator sums all components to give total water potential.

5. Frequently Asked Questions (FAQ)

Q1: What are typical water potential values in plants?
A: Leaf water potential typically ranges from -0.2 MPa (well-watered) to below -2 MPa (severely stressed).

Q2: How does water potential affect plant growth?
A: Lower (more negative) water potentials indicate water stress and can reduce cell expansion and photosynthesis.

Q3: What instruments measure water potential?
A: Pressure chambers, psychrometers, and tensiometers are common measurement devices.

Q4: Why is solute potential always negative?
A: Solutes reduce the free energy of water compared to pure water (reference state of 0).

Q5: How does water potential relate to water content?
A: The relationship is non-linear and described by moisture release curves in soils.