Question

Question 12 Discuss the factors responsible for ascent of xylem sap in plants.

Class XI Biology Chapter - Transport in Plants Page 193

Answer 1

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.

Answer 2

Xylem is responsible for the transportation of water and salts from the root. It is used for transpiration.