1.

What are the factors responsible for ascent of xylem sap in plants? 

Answer»
  • Cohesion: The mutual attraction between water molecules 
  • Adhesion: The attraction of molecules to polar surface e g., the surface of tracheary elements 
  • Surface Tension: The water molecules are attracted to each other in liquid phase more than to water in 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 tracheids and vessels.



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