1.

Explain the mechanism of ascent of sap

Answer»
  • A transpiration driven ascent of xylem sap depends mainly on the following physical properties of water 
  • Cohesion – mutual attraction between water molecule 
  • Adhesion attraction of water molecules polar surfaces such as tracheary elements. 
  • Surface tension -water molecules are attracted to each other in a liquid phase than in gas phase. 
  • These properties gives water ability to rise in the thin tubes. 
  • Water evaporates through stomata it results in pulling of water into leaf from the xylem transpiration can generate pull sufficient to lift a xylem sized column of water over 130 meters.


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