required practical

• Rate of Photosynthesis


  The rate at which photosynthesis occurs
• One graph may show the effect of many limiting factors
• The graph on the right shows how the rate of photosynthesis is affected by light intensity and temperature
• As light intensity increases


  The rate of photosynthesis increases
• When light becomes a limiting factor


  The rate of photosynthesis levels off
• At higher CO2 concentration (0.4%)


  The rate of photosynthesis levels off at a higher point than at lower CO2 concentration (0.04%)
• CO2 concentration was also a limiting factor at 0.04% CO2
• Temperature was not a limiting factor as it was the same (25°C) for both CO2 concentrations
• Oxygen production


  Shows the rate of photosynthesis
• Inverse square law

  • The relationship between light intensity and distance from the light source
• Measuring the rate of photosynthesis using Canadian pondweed

  1. Place light source at specific distances from pondweed

  2. Leave pondweed to photosynthesise for set time

  3. Measure length of O2 bubble produced

  4. Repeat with different light distances

  5. Can also measure effect of temperature or CO2 concentration
• Variables that could affect the results should be controlled, e.g. temperature and time the pondweed is left to photosynthesise
• The experiment is repeated twice at each light distance and the mean O2 volume is calculated