Transpiration

• What is transpiration ?

  water constantly evaporating from the surface of leaves
• What is the process of transpiration stream ?

  • evaporation of water from cells inside the leaf
  • water vapour than diffuses through the air spaces through the stomata
  • water passes through the xylem into the leaf to replace the water that has been lost
  • now water is drawn into the root hair cells and up the xylem vessels to the leaf
• What is the important process of transpiration ?

  • brings water to the leaf (for photosynthesis)
  • transports dissolved mineral ions e.g. magnesium
  • cools the leaf down mainly in warm weather
• What are the factors affecting transpiration ?

  • rate is greater at higher temperatures (evaporation is faster )
  • faster in dry conditions not humid (evaporation takes place quicker)
  • in windy conditions (wind removes any water vapour)
  • when light intensity increases (high light increases rate of photosynthesis )
• How do stomatas work ?

  • surrounded by two guard cells
  • when light intensity is high the guard cells swell and and change their shape (stomata opening )
  • carbon dioxide diffuse into the leaf and used in photosynthesis