Discuss the factors responsible for ascent of xylem sap in plants.
The transpirational pull is mainly responsible for the ascent of xylem sap in plants.
This ascent of water is facilitated by the following physical factors:
i. Cohesion - It is the mutual attraction between water molecules
ii. Surface tension - It is responsible for the greater attraction between water molecules in liquid phase than in gaseous phase.
ii. Adhesion - Attraction of water molecules to polar surfaces like the tracheary elements.
iv. Capillarity -Ability of water to rise in thin tubes
These physical properties give water high tensile strength, i.e., an ability to resist a pulling force and high capillarity, i.e., the ability to rise in thin tubes. The thin tubes of xylem work like capillary tubes.
