Question

During a severe drought, the soil becomes dry, and its water potential decreases. Many plants will wilt in such an environment. Consider that the overall water potential for a system is represented by the equation: Ψsystem = Ψtotal = Ψs + Ψp + Ψg + Ψm What is one reason that plants are unable to draw water from the soil?

a. The water potential of the soil becomes lower than the water potential of the plants.
b. The water potential of the soil becomes lower than the solute potential of the plants.
c. The water potential of the soil becomes higher than the water potential of the plants.
d. The solute potential of the soil becomes lower than the water potential of the plants.

Answer 1

Plants wilt during drought because the water potential of the dry soil drops below the plant's water potential, disrupting the normal water uptake.

Step-by-step explanation:

One reason that plants are unable to draw water from the soil during a severe drought is that the water potential of the soil becomes lower than the water potential of the plants. This is represented by option (a): "The water potential of the soil becomes lower than the water potential of the plants." If we consider the water potential equation Ψsystem = Ψtotal = Ψs + Ψp + Ψg + Ψm, where Ψs, Ψp, Ψg, and Ψm refer to solute, pressure, gravity, and matric potentials respectively, we understand that water moves from regions of higher water potential to regions of lower water potential. Thus, when the soil's water potential is lower due to drought conditions (becoming very negative), the gradient for water movement reverses, leading water to potentially move from the plant to the soil which contributes to plant wilting.