Topic 2 Main-Photosynthesis

• Limiting factors


  Raw materials that become the determining factor for the rate of photosynthesis
• Photosynthesis affects crop growth, and reducing limiting factors will increase crop growth
• Leaf arrangement on a plant ensures each leaf can absorb maximum light and is not shaded
• Leaf structure


  • Upper epidermis
  • Cuticle
  • Palisade mesophyll
  • Spongy mesophyll
  • Lower epidermis
  • Stomata
• Light absorption in a leaf

  Maximised by: short distance between upper and lower surfaces, large surface area, thin transparent cuticle, lack of chloroplasts in epidermis, presence of chloroplasts rich in chlorophyll, regular structure of palisade mesophyll
• Gas exchange in a leaf

  Maximised by: intercellular air spaces in spongy mesophyll, stomata+Stomata-allows carbon dioxide to enter and oxygen to leave
• During the day when photosynthesis is occurring

  Carbon dioxide enters the leaves and oxygen moves out
• At dawn and dusk when light intensity is low

  Rates of respiration and photosynthesis are equal (compensation point)
• Using hydrogencarbonate indicator to determine carbon dioxide movement


  Bright red in normal CO2, yellow in increased CO2, purple in decreased CO2
• Where does photosynthesis take Place

  Green parts of plants
• What is carbon dioxide and water made into during photosynthesis

  Glucose
• What is glucose converted into

  Starch
• What type of reaction is photosynthesis

  Endothermic
• What is produced as a waste product In photosynthesis

  Oxygen
• What is the word equation for photosynthesis

  Carbon dioxide+water——->glucose+oxygen
• What is light energy from the sun converted into

  Chemical energy
• How is glucose from photosynthesis used

  Respiration- to provide energy

  Useful substances-such as cellulose protein for growth

  Storsge-converted into starch and oils for storage
• What is the starch test

  1.Take a leaf from a plant kept in bright light

  2.Put leaf in boiling water- stops chemical reactions

  3.Put leaf in boiling alcohol- removes chlorophyll

  4.Dip leaf in water to soften it

  5.Add iodine solution
• How to destarch a plant

  Deprive it of light for two days
• What are the factors affecting rate of photosynthesis

  Temperature, carbon dioxide, water, light
• What is the optimum level

  The level at which photosynthesis takes place at its maximum rate
• The leaf


  The site of photosynthesis
• What are leafs adapted for

  Light absorption

  Gas exchange