Transpirational Pull

Definition - What does Transpirational Pull mean?

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 pull is a passive process that functions without any energy input from the plant. However, it is a critical process and is the strongest force that pulls and transports water to the leaves of all plants.

MaximumYield explains Transpirational Pull

While transpiration on its own refers to the loss of water in a plant through exposed surfaces, it is countered by the process of transpiration pull, where water is absorbed from the roots and spread throughout the plant, reaching all parts. Transpiration pull is a result of the evaporation of water from the surfaces of the cells in the leaves, which, in turn, is caused due to the attachment of the surface water to the pores of the cell walls.

The high surface tension of the water results in enough force to lift the water molecules as high as a hundred meters from ground level to a tree’s highest branches. However, at times, plant height hindrances in transpiration pull can trigger tension on the water columns, leading to a break and resulting in air bubbles. These bubbles compromise the plant's capillaries and damages the tree.

It is important to note that there are two types of transport tissues in plants: xylems and phloems. Both of them contain many capillary-like structures where capillary action takes place. Capillary action refers to the process where liquids such as water ascend the sides of narrow tubes through cohesion and adhesion.

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