Transpirational Pull And Cohesive Force Of Water

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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 as transpiration pull or transpiration tension. The water molecules within a column are joined to one another by a strong mutual force of attraction called cohesion force.
Its magnitudes is very high and account for the continuity of water column in xylem against its own weight and resistance caused by internal tissues in its translocation.

Thus transpiration tension draws water upwards by a force from roots and continuity of water column in maintained by cohesive force present amongst water molecules. This is the most widely accepted theory

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• Transpirational
• Pull
• And
• Cohesive
• Force
• Of
• Water