Write a note on transpiration pull theory.
Answers
In botany, transpiration pull refers to the suction, force, or pull that draws water up through a plant. It is a biological process where the water molecules and ions are absorbed up from the roots, and then evaporation occurs within the leaves, spreading water throughout the plant.
Transpiration theory, given by Dixon and Joly is also called as cohesion tension theory. This theory explains the role of transpirational pull in plant for water transport.
The transpirational pull is created by cohesive and adhesive forces between the water molecules and the xylem column. As the water is evaporated from the mesophyll cells of the plants, negative hydrostatic pressure is created which draws the water up from the veins of the leaves. This creates a negative tension in xylem tissues and that creates a negative tension in roots which draws the water from the soil.