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, and matrix effects.

2. How Does the Calculator Work?

The calculator uses the water potential equation:

Where:

• \( \Psi \) — Water potential (bars)
• \( i \) — Ionization constant (dimensionless)
• \( C \) — Molar concentration (mol/L)
• \( R \) — Pressure constant (0.0831 L bar/mol K)
• \( T \) — Temperature (Kelvin)

Explanation: The equation accounts for the effects of solute concentration and temperature on water potential.

3. Importance of Water Potential

Details: Water potential is crucial for understanding water movement in plants, soils, and cells. It helps predict the direction of water flow and is fundamental in plant physiology and soil science.

4. Using the Calculator

Tips: Enter the ionization constant (i), molar concentration in mol/L, and temperature in Kelvin. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What are typical values for water potential?
A: Pure water has Ψ = 0 bars. Most plant cells have Ψ between -1 to -3 bars. Dry soils can reach -15 bars or lower.

Q2: How does temperature affect water potential?
A: Higher temperatures increase the magnitude of solute potential (makes Ψ more negative) because it increases molecular movement.

Q3: What is the ionization constant (i)?
A: It represents the number of particles a solute dissociates into. For NaCl, i ≈ 2; for glucose, i = 1.

Q4: Why use Kelvin for temperature?
A: The Kelvin scale is an absolute temperature scale required for thermodynamic equations where zero means absolute zero.

Q5: How is this different from osmotic potential?
A: Osmotic potential is the solute component of water potential. Water potential also includes pressure and gravity components.