What drives the flow of water through the xylem?

Question

Quizplus · Accepted Answer

The flow of water through the xylem is primarily driven by transpiration, which is the process of water evaporation from the leaves. As water evaporates from the leaves, it creates negative pressure or tension forces which pull water up from the roots through the xylem vessels. This process is known as the transpiration-cohesion-tension mechanism.

Answer: E 
 Some species of plants have tracheid and vessel elements in their xylem tissue. These cells have pits and perforations that allow for active transport of water through the xylem. This process is known as the hydraulic mechanism and relies on the active pumping of water against gravity by tracheids and vessel elements to generate a positive pressure that can move water up the stem. However, this mechanism is not as prevalent as the transpiration-cohesion-tension mechanism.

What Drives the Flow of Water Through the Xylem