B1.9 - Factors Affecting Photosynthesis

• What is the inverse square law?

  • The inverse square law states that the intensity of light decreases proportionally to the square of the distance from its source.
  • For example, if the distance is doubled, the light intensity decreases to 1/4 of its original value.
  • The formula is:

  I ∝ d21​

  Where:

  I = light intensity

  d = distance between light source and object
• What is the role of chlorophyll?

  To absorb light energy for photosynthesis
• Why may plants produce insufficient chlorophyll?

  • They lack the required nutrients 
  • They have a disease like Tobacco Mosaic Virus
• In addition to the amount of chlorophyll that a plant has, there are three environmental factors that affect the rate of photosynthesis. What are they?

  • Light intensity 
  • Amount of carbon dioxide
  • Temperature 
• • Light intensity 
  • Carbon dioxide concentration 

  
• Temperature

  
• Carbon dioxide concentration 

  
• Plateaued/stayed the same.

  
• • Carbon dioxide concentration 
  • Temperature

  We can see that the rate of photosynthesis is no longer increasing as light intensity increases. This means that another factor (such as carbon dioxide or temperature) must be limiting the rate.

  
• Farmers in cooler climates often use greenhouses. These help trap the heat energy from sunlight, and so increase the temperature. They also keep out pests which could otherwise damage the plants. 
• How can farmers ensure that photosynthesis takes place 24 hours a day?

  Use artificial lighting 
• What do plants need to carry out photosynthesis?

  Light, carbon dioxide, temperature, chlorophyll
• How does chlorophyll affect photosynthesis?

  Less chlorophyll means less photosynthesis
• What can cause a plant to have less chlorophyll?

  Disease, environmental stress, lack of nutrients
• What are the limiting factors for photosynthesis?

  Light, carbon dioxide, and temperature
• What is plotted on the x-axis of photosynthesis graphs?

  Light, carbon dioxide, and temperature
• What happens to the rate of photosynthesis as light intensity increases?

  The rate of photosynthesis increases
• What does it mean when the graph of photosynthesis plateaus?

  Another factor is limiting photosynthesis
• How does carbon dioxide concentration affect photosynthesis?

  Higher concentration increases the rate
• What happens to the rate of photosynthesis at high temperatures?

  It initially rises, then drops due to denaturation
• At what temperature are enzymes fully denatured?

  About 45 degrees Celsius
• What does a graph with two curves represent?

  Different experiments with varying conditions
• How can comparing two curves on a graph indicate a limiting factor?

  It shows how conditions affect photosynthesis rates
• What might farmers do to enhance photosynthesis in greenhouses?

  Provide heat, light, and carbon dioxide
• Why do farmers use greenhouses?

  To trap heat and protect plants
• What is one benefit of using fertilizers in farming?

  Ensures plants have essential minerals
• What must farmers consider when increasing production costs?

  Extra costs versus potential crop yield
• What are the main factors affecting the rate of photosynthesis?

  • Light intensity
  • Carbon dioxide concentration
  • Temperature
  • Amount of chlorophyll
• How do farmers create optimal conditions for photosynthesis?

  • Use greenhouses to trap heat
  • Provide artificial light
  • Pump carbon dioxide into greenhouses
  • Use fertilizers for essential minerals
  • Apply pesticides to control pests
• How do temperature and enzyme activity relate to photosynthesis?

  • Rate increases with temperature initially
  • Enzymes denature at high temperatures
  • Rate drops to zero when enzymes are denatured
• How do graphs help in understanding photosynthesis?

  • Show relationships between factors
  • Indicate limiting factors
  • Compare different experimental conditions