Demostrating transpiration. Image credit

Demostrating transpiration. Image credit

ZIMSEC O Level Combined Science Notes:Transpiration in plants

  • Water enters plant roots at all hours of the day.
  • Some trees absorb as much as 5 litres of water per minute.
  • Over 95% of the water that enters a plant through the roots exits the plant via the leaves.
  • Only a small amount of the water is used for processes inside the plant.
  • The loss of water via the leaves is known as transpiration.
  • Transpiration is the loss of water vapour from the leaves of a green plant.
  • Water is lost from all plant surfaces but it is lost mainly through the leaves.
  • As water is lost into the atmosphere it evaporates and helps to keep the plant cool.
  • As water is lost through the plant stem and leaves more is brought in by the roots to replace the water that is lost.
  • Water and ions from the soil enter the plant and move up through the plant.
  • The water and ions are transported to all parts of the plant.
  • It is used in processes like photosynthesis and growth.
  • The rate of transpiration varies from plant to plant and from day to day.
  • When a plant losses more water that it can absorb through the soil it wilts.
  • This is because the plant cells lose water and become soft/limp.
  • The cells lose their turgor (hardiness) and the leaves hang down.
  • Sometimes the whole plant droops.
  • If the loss continues to occur the plants will die.

To access more topics go to the Combined Science Notes page.

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