Correct option is D
Explanation:
Let's evaluate each statement about water potential (ψ) in plants:
A. The major factors influencing the water potential in plants are potentials of solutes (ψ_s), pressure (ψ_p), and gravity (ψ_g).
This statement is correct. The total water potential (ψ) in plants is determined by the sum of three components:
Solute potential (ψ_s), which is affected by the presence of solutes.
Pressure potential (ψ_p), which refers to the physical pressure exerted on or by the water.
Gravitational potential (ψ_g), which depends on the height of the water in relation to a reference point. Therefore, A is correct.
B. The solute potential (ψ_s) increases the free energy of water by diluting the water.
This statement is incorrect. Solute potential (ψ_s) actually decreases the free energy of water. When solutes are added to water, they bind with water molecules, making the water less free to move. This reduces the free energy of the water. So, B is incorrect.
C. Positive pressures raise the water potential while negative pressures reduce it.
This statement is correct. Positive pressure increases the water potential (ψ), as pressure tends to push water into a cell or space, making it more likely for water to move. On the other hand, negative pressure (like tension or suction) reduces the water potential because it tends to pull water out of a cell or space. So, C is correct.
D. The gravitational potential depends on the height of the water above the reference-state of water, the density of water, and the acceleration due to gravity.
This statement is correct. Gravitational potential (ψ_g) is indeed determined by the height of the water, the density of water, and gravity. It represents the energy associated with the position of the water relative to the earth's surface, calculated using the formula:
ψg=ρgh\psi_g = \rho g hψg=ρghwhere ρ is the density, g is the gravitational acceleration, and h is the height. So, D is correct.
