Name: Transport of Water in Plants
Uploaded: 2019-07-19
Duration: 4 min 42 s
Description: Plants need water. The water transport system in plants is like a canal system. Explore this transport system from the root hair to the various parts of the...

Question

Define and explain water potential?

Accepted Answer

The difference between the free energy of water molecules in pure water and the energy of water in any other systems like Water in a solution or in a plant cell or tissue is called the water potential, and it is measured in pascals (Pa). Water potential is indicated by the Greek symbol Ψ (Psi). It is a comparative measure and the water potential of pure water is arbitrarily set at zero. So, the water potential of a solution is always represented in negative values. If some solute is suspended in pure water, the solution has less free water molecules and the concentration of free water molecules drops and decrease its water potential. So, all solutions have a lower water potential than pure water.

The quantum change in Ψ value on account of the addition of solute is called solute potential Ψ_s is always negative. The more the solute molecules, the lower is Ψ_s. For a solution at atmospheric pressure Ψ_w (water potential) is equal to Ψs (solute potential). If a pressure higher than atmospheric pressure is given to pure water or a solution, then its water potential raises. The cell converts turgid due to the entry of water into the cell. The quantity of increment in water potential in such cell is named Pressure potential. It is generally positive and is indicated as Ψ_p. The water potential of a cell is influenced by both solute and pressure potentials. The relation between them is Ψ_w = Ψ_s +Ψ_p.

Define and explain water potential?

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