(6) plant nutrition

• Photosynthesis


  Plants synthesise carbohydrates from raw materials using energy from light
• Chlorophyll


  A green pigment found in chloroplasts
• Chlorophyll


  Converts light energy into chemical energy for the synthesis of carbohydrates
• Carbohydrates in plants used for

  • Starch as energy store
  • Cellulose to build cell walls
  • Glucose in respiration to provide energy
  • Sucrose for transport in phloem
  • Nectar to attract insects for pollination
• Magnesium


  Makes chlorophyll, deficiency leads to yellow leaves
• Nitrate ions


  Make amino acids, stunted growth
• Factors affecting photosynthesis


  • Light intensity
  • Carbon dioxide concentration
  • Temperature (enzyme)
• Limiting factors


  Light, carbon dioxide, temperature
• Waxy cuticle


  Thin, prevents water loss
• Guard cells


  Open/close stomata for diffusion (carbon dioxide in, oxygen out) also contains chloroplasts
• Stomata


  Allow diffusion of gases in and out
• Upper/lower epidermis


  Protect inner cells, have no chloroplasts, thin allows more light to reach
• Palisade mesophyll


  Closely packed, many chloroplasts
• Spongy mesophyll


  Air spaces, allow diffusion of gas