Question

Water potential of pure water and its solution are –
A. $0$ and $1$
B. $0$ and $0$
C. $0$ and more than $1$
D. $0$ and less than zero.

Answer 1

Water potential – The difference between the free energy of water molecules in pure water and the energy of water in any other system (Example: Water in solution) is termed as water potential.

Complete answer:
Let us analyse the options to find the correct answer.

Option A, B and C: As the water potential is $0$ or less than $0$ as some solute is being added to the solvent. Therefore, these options are incorrect.
Option D: The pure water at atmospheric pressure, has zero water potential. The water potential of a solution can be determined by using pure water as the standard. When the solution is prepared, a solute is added to the solvent. The presence of solute particles reduces the free energy of water and thus decreases the water potential. Therefore, water potential of a solution becomes negative i.e. less than zero. Therefore, this is the incorrect option.

Additional information: In plants various Plant water relations are seen as water is important for both animals and plants. The various relations are,

Water potential - Water has some amount of kinetic energy and thus, greater the amount of water in the system greater is its kinetic energy.
Osmosis - It can be defined as the process by which water moves across a semipermeable membrane from a higher concentration to lower concentration.
Imbibition - It is the process by which the water is absorbed by solids leading to increase in its volume
Plasmolysis - It is the process by which the water moves out of the cell and leads to shrinking away of cell membrane from the cell wall.

Hence, the correct answer is option (D).

Note: Greek word $\psi$(psi) designates the water potential. The water potential is expressed in pressure units such as Pascals (Pa), bar or atmospheres. Plants use water potential to transport water to leaves for photosynthesis.