Gas Exchange in Plants

• What are Mesophytes?

  Plants adapted to a habitat with adequate water
• What are Xerophytes?

  Plants adapted to a dry habitat
• What are Halophytes?

  Plants adapted to a salty habitat
• What are Hydrohytes?

  Plants that are adapted to a freshwater habitat
• How are plant leaves adapted to increase Surface Area?

  • Wide and Flat
  • Spongy Mesophyll are spaced far apart
• How are plants adapted to decrease diffusion distance?

  • Thin
  • Spongy Mesophyll create air spaces
• How do plants maintain a carbon dioxide concentration gradient?

  • Wind circulates air around the leaf
  • Carbon dioxide is constantly being used by photosynthetic cells
• How is Marram Grass adapted to reduce water loss?

  • Thich waxy cuticle
  • Small leaf SA:Vol ratio
  • Sunken stomata
  • Leaf hairs around stomata
  • Rolled leaves
• How are Cacti adapted to increase their water uptake?

  • Wide reaching roots
  • deep roots
• Why can’t blocks be used to model SA:Vol ratio?

  • They’re a regular shape, cells are not
  • They don’t have a selectively permeable membrane
  • Much bigger than cells
• Why do plants close their stomata at hours of darkness?

  • Need light for photosynthesis
  • No light
  • So need to gain carbon dioxide
• Why can’t water evaporate directly from the surface of the leaf?

  • Leafs are covered in a waxy cuticle
  • This is hydrophobic
  • So no water can pass through
• What does a Thick Cuticle do?

  Stops uncontrolled evaporation from leaf cells
• What does small leaf surface area to volume ratio do?

  Reduces evaporation
• What does putting stomata in sunken pits do?

  Maintains humid air around the stomata to create a shallower concentration gradient
• What do leaf hairs do?

  Maintains humid air around stomata to create a shallower concentration gradient
• What do rolled leaves do?

  Maintains humid air around stomata to create a shallower concentration gradient
• What do Deep Roots do?

  Access to deep water sources
• What do widespread shallow roots do?

  Rapid access to rainwater