Question

Which theory of water transport in xylem can also be used to explain the primary movement of water in nonvascular plants such as mosses? A) cohesion-tension B] capillarity C) proton pump D) air pressure E) active transport by tracheid and vessel elements

Answer 1

The correct answer is: A) cohesion-tension

Water movement in xylem of plants is passive process that is driven by pressure and chemical potential gradients. Xylem is plant tissue that transports water from roots to leaves. This upward water flow (against the force of gravity) through the xylem of plants is possible because of water properties.

Cohesion refers to cohesive force between water molecules which attracts them towards each other. As a result surface tension in liquid water occurs.

Tension is the result of transpiration. Negative pressure is generated by the evaporation of water from the leaves (transpiration).  

So, transpiration pull (via capillary action and the inherent surface tension of water) is responsible for water movement upwards.