To understand the mechanism of transpirational pull.
An activity demonstrating transpirational pull.
Materials required:
  • Two small pots one with a plant and other with a stick
  • Plastic sheet
  • Take two small pots of similar sizes with the same amount of soil.
  • One pot should contain a plant and the other with a stick of the same height as the plant.
  • Cover the soil present in both the pots with a plastic sheet so that the moisture doe not escape by evaporation.
  • Now cover both the pots, one with the plant and the other with the stick with plastic sheets and place them under bright sunlight for about half an hour.
  • After half an hour, try observing the changes in both setups.
The experimental set up for transpirational pull
Water droplets will be found on the plastic sheet having plant, and no water droplets will be found on the plastic sheet which covers the stick.
We know that plants liberate water molecules into the air through transpiration. However, as the plant is covered with a plastic sheet, it does not allow the water molecules to escape. Due to this, water droplets appear on the plastic sheet. This does not occur in the pot without the plant due to the lack of transpiration. But, in few cases, water droplets appear due to the process of evaporation.
Thus, we can conclude that the transpiration in plants creates a pressure (transpirational pull) in the roots, resulting in water and mineral absorption.