plant structure and function

• Photosynthesis

  • Carbon dioxide, water, glucose and oxygen
• Water and mineral ion uptake

  1. Osmosis

  2. Active transport in shoot tips
• Water and mineral ion uptake

  • Large surface area
  • More water can move in
• Photosynthesis


  1. Light energy transferred to chloroplasts in leaves

  2. Endothermic reaction, takes in more energy than it releases
• Limiting factors of photosynthesis

  • Temperature
  • Light intensity
• Temperature increases


  Rate of photosynthesis increases until enzymes denature
• Light intensity increases


  Rate of photosynthesis increases
• Plant structure and function

  • Large permanent vacuole affects speed of water movement
  • Mitochondria provide energy for active transport
  • Xylem transports water and mineral ions
  • Lignin deposited in cell walls to withstand water pressure
  • Phloem transports products of photosynthesis
• Carbon dioxide concentration needed to make glucose
• Interaction of limiting factors
• Light intensity core practical
• Inverse square law


  As distance increases, light intensity decreases
• Stomatal movement


  1. Cells change shape to open and close

  2. Allows gas exchange
• Translocation


  Movement of food made in leaves up or down phloem
• Leaf adaptations


  • Overlapping veins
  • Thick inner cell walls, thin outer walls
  • Increased air movement around leaf
  • Steep concentration gradient for water vapour
• Extreme plant adaptations


  • Leaf shape and size reduced
  • Waxy cuticle prevents evaporation
• Positive phototropism


  Auxins move to shaded side, stimulating growth
• Negative gravitropism (horizontal shoot)


  Auxins move to lower side, cells grow more, shoot bends and grows away
• Positive gravitropism (horizontal root)


  Auxins move to lower side, cells grow more, root bends and grows downwards
• Chlorophyll is the most efficient colour to absorb light
• Leaf thinness allows short CO2 diffusion distance
• Large leaf surface area allows more light absorption
• Temperature increases


  Transpiration rate increases
• Relative humidity increases


  Transpiration rate decreases
• Uses of plant hormones: weed killers, rooting powders, tissue culture growth
• Gibberellins allow seed germination and fruit growth
• Ethene controls fruit ripening
• Advantages of MRSA: engineered to target only unhealthy cells, not affect healthy cells
• FSH stimulates ovary maturation
• Optimum, denatured, optimal