Plant nutrition

• Photosynthesis


  A process which plants carry out to produce food by synthesising carbohydrates and oxygen from water and carbon dioxide using sunlight and chlorophyll
• Photosynthesis


  1. Water and carbon dioxide absorption

  2. Energy absorption from sunlight

  3. Production of glucose and oxygen
• The balanced chemical equation for photosynthesis is 6CO2 + 6H2O —> C6H12O6 + 6O2
• Plants can release CO2 at night or in dark spaces
• Chlorophyll


  Captures energy from sunlight to facilitate photosynthesis
• Leaf functions


  • Maximise light absorption
  • Maximise carbon dioxide absorption
• External parts of a leaf

  • Blade/Lamina
  • Leaf Margin
  • Apex
  • Base
  • Petiole
  • Midrib
  • Veins
  • Stipule
• Blade/Lamina


  • Rich in chlorophyll
  • Wide surface area
  • Thin for maximum light penetration
• Petiole


  Leaf stalk that arranges the leaf to avoid overlapping
• Midrib


  • Runs from petiole to tip
  • Supports the blade
• Veins


  • Provides support
  • Distributes water and food
• Cuticle


  A waxy waterproof layer that decreases transpiration
• Epidermis (upper)


  • Outer protective layer
  • Thin and transparent
• Palisade Mesophyll


  • Located near the surface
  • Contains most chloroplasts
  • Absorbs most CO2
• Xylem


  Transports water and mineral ions
• Phloem


  Transports cell sap
• Spongy Mesophyll


  • Irregularly shaped for gas exchange
  • Contains fewer chloroplasts
• Epidermis (lower)


  • No cuticle
  • Filled with stomata and guard cells
• Stomata


  Small pores for gas exchange
• Guard cell


  Specialised cell that opens and closes stomata
• Palisade cell adaptations

  • Thin cell wall
  • Packed with chloroplasts
  • Large central vacuole
  • Thin cytoplasm
  • Small size
• Factors affecting rate of photosynthesis

  • Carbon dioxide concentration
  • Light intensity
  • Temperature
• As CO2 concentration increases


  The rate of photosynthesis increases
• As light intensity increases


  The rate of photosynthesis increases until temperature becomes a limiting factor
• Photosynthesis occurs because enzymes are present with an optimum temperature of about 25 degrees
• At low temperatures


  Enzymes and substrates move slower, slowing photosynthesis
• At high temperatures


  Enzymes denature, slowing photosynthesis
• Requirements for photosynthesis


  • Carbon dioxide
  • Chlorophyll
  • Light
• Testing for starch in a leaf

  1. Destarch leaf

  2. Cover part with dark paper

  3. Expose to sunlight

  4. Boil in water

  5. Soak in ethanol

  6. Test with iodine
• Producing oxygen with pondweed

  1. Inverted test tube over funnel

  2. Observe water level decrease

  3. Test gas with glowing splint
• Independent variables in experiments

  • Light intensity
  • Carbon dioxide concentration
  • Temperature
• Constant variables in experiments

  • Mass and type of pondweed
  • Time
  • pH
• Safety measures include using gloves and goggles
• Main parts of a glasshouse


  • Glass
  • Artificial lighting
  • Heater
  • Ventilation
  • Carbon dioxide supply
  • Water supply
  • Humidifier
• Nutrients essential for healthy plant growth

  Nitrogen<|>Phosphorus<|>Magnesium<|>Potassium
• Nitrogen


  • Enters soil through nitrogen fixation
  • Forms amino acids and proteins
• Phosphorus


  • Makes DNA and RNA
  • Makes ATP for respiration
• Magnesium


  • Forms chlorophyll
• Potassium


  • Essential for healthy leaves and flowers
• Uses of glucose produced in photosynthesis


  • Made into cellulose
  • Stored as starch
  • Respired for energy