Transpiration

• Transpiration


  The process of water constantly evaporating from the surfaces of leaves
• Transpiration process


  1. Water evaporates from cells inside the leaf

  2. Water vapor diffuses through air spaces in the spongy mesophyll

  3. Water vapor exits the leaf through the stomata

  4. Water passes from the xylem into the leaf to replace lost water

  5. Water is drawn into the root hair cells and up the xylem vessels to the leaf
• Importance of transpiration


  • Brings water to the leaf for photosynthesis
  • Transports dissolved mineral ions
  • Cools the leaf down in warm weather
• Factors affecting rate of transpiration

  • Higher temperatures
  • Dry conditions (low humidity)
  • Windy conditions
  • Higher light intensity
• High light intensity

  Stomata open to allow carbon dioxide to enter for photosynthesis, allowing water vapor to pass out
• Stomata


  Pores on the leaf surface surrounded by guard cells
• Stomata opening and closing

  1. Guard cells swell and change shape in high light, causing stomata to open

  2. Plant closes stomata under hot conditions to reduce water loss
• Stomata and guard cells play roles in gas exchange and water loss in plants