Question

What is transpiration pull? How is it caused?

Answer 1

As the water is lost from the leaf surface by transpiration, more water molecules are pulled up due to the tendency of water molecules to remain joined (cohesion), and thus to produce a continuous column of water through the stem is called transpiration pull. Transpiration pull is an important force which causes the ascent of sap. Negative pressure or tension is produced in the xylem that pulls the water from the roots and soil.