Final answer:
Water normally moves from soil to plant roots due to water potential gradients, but during drought conditions or when soil is overly saturated, this can be disrupted.
Step-by-step explanation:
Under normal circumstances, water moves from the soil into a plant's roots, a process driven by water potential gradients. However, this process can be disrupted in certain conditions.
For example, during drought conditions, the water potential of dry soil becomes more negative compared to the plant's water potential; hence, water moves from areas of higher to lower water potential.
As a protective mechanism, plants will close their stomata to conserve water, and they may shed leaves to reduce transpiration. In such situations, water might not move from the soil into the plant's roots efficiently.
Another circumstance might include overly saturated soil during instances of heavy rainfalls, leading to surface runoff, where the water might preferentially flow over the surface or percolate into the subsoil to become groundwater, rather than being absorbed by the plant's roots.