NEET BIOLOGY

Detailed explanation-1: -This tension is transmitted to the roots. The molecules of water show cohesion and molecules of water and vessel wall show adhesion. Because of cohesive and adhesive forces, water column does not break and is pulled upward by the force called as transpiration pull.

Detailed explanation-2: -The ascent of sap in the xylem tissue of plants is the upward movement of water and minerals from the root to the aerial parts of the plant. The conducting cells in xylem are typically non-living and include, in various groups of plants, vessel members and tracheids.

Detailed explanation-3: -The transpiration driven ascent of xylem sap depends mainly on the following physical properties of water-cohesion, adhesion and surface tension. These 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.

Detailed explanation-4: -The theory states that transpiration pull or tension, cohesion property of water, and hydration of the cell walls (i.e., adhesion) are collectively responsible for the ascent of sap. Water movement through the xylem is a bulk flow caused by p (pressure difference) between one end of the system and the other.