Question

Explain transpirational pull theory in a short form

Answer 1

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 mesophyll 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 stem which take water from Xylem of roots. Thus, water flow in a channel. This water channel is held together by cohesion force (force of attraction between water molecule), Adhesion (force of attraction between water molecules and walls of cells) and keeps the water column in the place. It is known as transpirational pull.