Recall questions

• What features do all gas exchange surfaces have in common?

  Large surface area, Thin walls, Good ventilation
• What gases do plants need and why?

  Carbon dioxide for photosynthesis AND Oxygen for respiration
• What is the main gas exchange surface in plants?

  Spongy mesophyll
• Where do gases move in and out of plants?

  Stomata
• Give one adaptation of leaves to gas exchange?

  Large surface area with lots of air spaces in spongy mesophyll
• Describe how stomata help to control water loss?


  When plants have little water, potassium ions are actively moved out of the guard cells causing water to leave by osmosis down the concentration gradient. This causes the guard cells to become flaccid so they close the stoma
• Describe an adaptation of plants that live in dry environments?

  Few stomata to help reduce water loss