The basic elements of the cohesion theory for the ascent of sap are

✅ Explanation: The cohesion-tension theory explains how water moves up from the roots to the leaves of plants, even against gravity. This theory relies on three primary elements:
Driving force: Transpiration from leaves creates a negative pressure or tension, pulling the water column upwards.
Cohesion of water: Water molecules stick together due to hydrogen bonding, maintaining a continuous column in the xylem.
Hydration: Adhesion of water molecules to the xylem walls helps prevent the water column from breaking under tension.

🔑Key Points :
-The movement of absorbed water molecules against the pull of gravity to the topmost parts of the plant is called ascent of sap. 

✏️Three main theories regarding ascent of sap are:
-Vital-Force Theory – It includes Godlewski‟s Relay-Pump Theory, Bose‟s Pulsatory Movement Theory, 
-Root-Pressure Theory
-Physical-Force Theory – It include Boehm‟s Theory, Imbibition Theory of Sachs, Cohesion-Tension Theory
-The most widely accepted theory for the ascent of sap in trees is the ''Transpiration pull and cohesion theory;'' 
-It was given by Dixon & Jolly 

✏️The transpiration driven ascent of xylem sap depends mainly on the following physical properties of water:
-Cohesion – the mutual attraction between water molecules.
-Adhesion – attraction of water molecules to polar surfaces (such as the surface of tracheary elements).
-Surface Tension – water molecules are attracted to each other in the liquid phase more than to water in the gas phase.
-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.
-In plants, capillarity is aided by the small diameter of the tracheary elements – the tracheids and vessel elements.

• 🛑Additional Information:
Bose's Pulsatory Movement Theory – 
-Sir J.C. Bose (1923) said that living cells of the innermost layer of the cortex of a plant, just outside the endodermis are in rhythmic pulsations.
-Such pulsations are responsible for pumping the water in an upward direction.
-According to Bose, the pulsatory cells pump the water into vessels.