Question

What are the physical properties of water responsible for the ascent of sap through xylem in plants?

Answer 1

• The ascent of sap in the xylem tissue of plants. is the upward movement of water and minerals from the root to the upper parts of the plants such as leaf, stem etc. Factors responsible for the ascent of xylem sap in plants - Transpiration driven ascent of xylem sap is dependent chiefly on the physical properties of water that are the following:
  
• Cohesion: The mutual attraction between water molecules.
  
• Adhesion: The attraction of molecules to polar surfaces e.g., the surface of tracheary elements (tracheids and xylem vessels)
  
• Surface tension: The water molecules are attracted to each other in a liquid phase more than to water in the gas phase.
  
• All these properties provide water high tensile strength (an ability to resist a pulling force) as well as high capillarity (ability to rise in a thin tube). In plants, capillarity is aided by the small diameter of both tracheary elements (tracheids and vessels).