Factors Affecting Rate of Photosynthesis

Question 1

What are the factors affecting rate of photosynthesis?

Answer 1

• light intensity
• CO2 concentration
• temperature
• supply of water
• presence of photosynthetic pigments

Question 2

Light Intensity Notes

Answer 2

• Higher light intensity, faster light dependent stage of photosynthesis
• Produces more ATP and reduced NADP for calvin cycle
  .
  A decrease in light intensity causes :
• Decrease in TP and RuBP concentration
• Slight increase in GP concentration
  (less light available, NADPH and ATP do not form, so GP builds up because it is not converted to TP, lack of TP means RuBP will not form)

Question 3

CO2 Concentration notes

Answer 3

• CO2 is combined with Ribulose Bisphosphate during carbon fixation
• SO more CO2 present means calvin cycle can occur faster
• Increasing levels of CO2 can be toxic
  .
  Low concentrations of CO2 cause a decrease in GP and TP concentration, but increase in RuBP. RuBP accepts CO2, so when theres no CO2, RuBP builds up. Lack of CO2 fixation means GP and TP do not form

Question 4

Temperature Notes

Answer 4

• Temp increase, rate of photosynthesis in light independent stage increases
• Enzymes control the reactions
• Temp increase to a point, then enzymes denature
• Increasing temp can cause stomata to close to reduce water loss, CO2 cannot enter leaves, photosynthesis slows
• In light dependent reaction, proton move across thylakoid membrane, whose permeability can be influenced by high temperatures

Question 5

How can all this be used in agriculture?

Answer 5

• Greenhouses can be used to maximise crop yield
• Sensors can monitor light intensity, humidity and CO2 concentration
• Water irrigation systems
• Fertilisers
• Natural pests or pesticides
• Crop yield, environmental damage, and cost of maintenance need to be considered