Rate of photosynthesis

• What does a limiting factor do?

  Restrict rate of photosynthesis (stop from increasing) if in low levels.
• Describe and explain how temp affects rate of photosynthesis

  1. As the temp increases, rate increases ( so temperature = limiting factor)
  2. as enzymes controlling photosynthesis gain kinetic energy
  3. Above an optimum temperature, rate decreases
  4. as enzymes denature (active site changes shape)
• Describe and explain how light intensity affects rate of photosynthesis

  1. As light increases, the rate increases (so light intensity = limiting factor)
  2. As light provides energy needed for photosynthesis
  3. above a certain light intensity, rate stops increasing
  4. another factor is limiting e.g temperature / co2
• Describe and explain how co2 concentration affects the rate of photosynthesis

  1. As the conc increases, the rate increases (so co2 conc = limiting factor)
  2. as co2 is a reactant / raw material needed for photosynthesis
  3. Above a certain co2 concentration. , rate stops increasing
  4. another factor is limiting e.g temp / light intensity
• How does chlorophyll affect the rate of photosynthesis?

  Affects how much light energy can be absorbed
• what law describes the relationship between distance of a light source from a plant and light intensity?

  Inverse square law
• How can farmers use their knowledge of limiting factors to increase their profits? (HT only)

  • Remove limiting factors → gain maximum rate of photosynthesis → increase plant yeild
  • Profit from extra yield must be greater than the costs of providing conditions
• Common misconceptions: water is a limiting factor

  It is not considered a limiting factor as the volume needed is very small and water shortages affect other processes in the plant before affecting photosynthesis
• What factor is most likely to limit the rate if photosynthesis in plants in a greenhouse on hot summer's day ? explain why.(4)

  • Carbon dioxide concentration
  • As atmospheric carbon dioxide concentrations. is very low
  • Temperature is high
  • Light intensity is high