Transpiration

• Transpiration


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


  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 the lost water

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


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

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


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


  Pores on the leaf surface that allow gas exchange
• Guard cells


  Cells that surround the stomata and control their opening and closing
• Stomata opening and closing

  1. High light intensity: Guard cells swell, causing stomata to open

  2. Hot conditions: Plant closes stomata to reduce water loss