Limiting factors

• Law of limiting factors


  At any given moment, the rate of a physiological process is limited by the factor that is at its least favourable value
• Factors that can limit photosynthesis


  • Light intensity
  • Temperature
  • CO2 concentration
• Usually only one factor is limiting at a time
• The overall rate of photosynthesis is determined by the rate of whichever steps in the process is proceeding most slowly
• The rate of photosynthesis is partly dependent on light intensity
• Compensation point - At a particular light intensity, the rate of photosynthesis matches the rate of respiration (volume of CO2 taken in = volume of CO2 released)
• Oxygen is used as quickly as it is produced
• The compensation point is reached as light intensity increases/ decreases- early mornings and late evening
• Photosynthesis occurs at a slower rate at the compensation point, respiration is relatively constant
• If the light intensity increases beyond the compensation point, the rate of photosynthesis increases proportionally
• Light intensity

  A) Rate of photosynthesis

  B) Light intensity

  C) Plenty of CO2 and heat

  D) CO2 or temp needs to be increased

  
• CO2 concentration

  A) Rate of photosynthesis

  B) Light or temp needs to be increased

  C) Plenty of light and warmth

  D) CO2 concentration

  
• Temperature

  Increased temp = increased energy and rate of photosynthesis

  A) Rate of photosynthesis

  B) enzymes denature

  C) temperature

  
• Provided that other factors are not limiting, the rate of photosynthesis increases in direct proportion to the temp
• Between 0-25 degrees Celsius, the rate of photosynthesis is approximately doubled for each 10 degree rise in temperature
• Light intensity

  • Electrons do not leave chlorophyll
  • ATP is not synthesised
  • NADP is not reduced
  • reduction of GP into TP is reduced
• CO2 concentration

  • Carbon does not combine with RuBP to make GP
  • RuBP and NADP build up
• Temperature

  • Rubisco is an enzyme
  • No GP formation