Plants

• Explain how the leaves of dicotyledonous plants are adapted for gas exchange

  • Many stomata (high density) - large surface area for gas exchange
  • Spongy Mesophyll contains air spaces - large surface area for gasses to diffuse through
  • Thin - Short diffusion pathway
• What is a xerophyte?

  A plant adapted to live in very dry conditions e.g. cacti and marram grass
• Explain structural and functional compromises in xerophyte plants that allow efficient gas exchange while limiting water loss

  1)Thicker waxy cuticle

  • Increases diffusion pathway so less evaporation

  2)Sunken stomata in pits/rolled leaves/hairs

  • Traps water vapour/protects stomata from wind
  • So reduced water potential gradient between leaf/air
  • Less evaporation

  3)Spines/Needles

  • Reduces SA:Vol ratio