Transpirational pull is responsible for the ascent of water in the xylem. This ascent of water is dependent on the following physical factors:

• Cohesion – Mutual attraction between water molecules
• Surface tension – Responsible for the greater attraction between water molecules in liquid phase than in gaseous phase
• Adhesion – Attraction of water molecules to polar surfaces
• Capillarity –Ability of water to rise in thin tubes.

These physical properties of water allow it to move against gravity in the xylem.