The cohesion-tension theory explains the movement of water from roots to leaves in xylem vessels in plants.

It suggests that water is pulled up through the plant under tension, due to the transpiration pull and the cohesive and adhesive properties of water.

Adhesion is the attraction of polar water molecules to the non-polar cellulose in xylem vessel cell walls.

This helps water to rise through the plant against gravity.

Cohesion is the attraction between polar water molecules due to hydrogen bonding.

This helps water molecules stick together and move up the plant as a continuous column in the xylem vessels.

The transpiration pull is the upward movement of water from the roots to the aerial parts of a plant, driven by the evaporation of water from the leaves.

1. Water enters a plant's root hair cells via osmosis 
2. It moves through cell cytoplasm or cell walls towards the xylem
3. The xylem transports water from the roots up to the leaves