How do cohesion and adhesion that exist in the xylem of a plant?
The attraction between two like molecules is called cohesion.Water has an unusually high cohesive force again due to the 4 hydrogen bonds each water molecule potentially has with any other water molecule. The attraction between two unlike molecules is called adhesion.Because both water and cellulose are polar molecules there is a strong attraction for water within the hollow capillaries of the xylem. Transpiration Pull and Cohesion theory: This theory was proposed by Dixon and Jolly (1894). According to this theory leaves loose water into atmosphere by transpiration. This in turn decreases water potential of mesophy II cells. These cells draw water from adjacent cells having high water potential. This potential gradient extends upto sap of xylem.As a result, a tension is created in xylem elements of leaf which is transmitted down to the xylem elements of leaf which is transmitted down to the xylem elements of root.This puts the water in xylem to a great pull or tension. This is known a
