The rate of photosynthesis

• What three factors affect the rate of photosynthesis?


  Light intensity, CO₂ concentration, and temperature
• Why is water considered a limiting factor in photosynthesis?


  Because a severe shortage of water can hinder the process of photosynthesis
• What are the limiting factors that can affect the rate of photosynthesis?


  • Light intensity
  • CO₂ concentration
  • Temperature
  • Chlorophyll levels
• What does it mean when a factor is described as the limiting factor in photosynthesis?


  It means that the factor is preventing photosynthesis from occurring at a faster rate
• Which factor is typically limiting at night for photosynthesis?


  Light intensity
• What is often the limiting factor for photosynthesis during winter?


  Temperature
• When are CO₂ levels usually the limiting factor for photosynthesis?


  When it is warm enough and bright enough
• How can chlorophyll become a limiting factor in photosynthesis?


  By being affected by disease or environmental stress, reducing its ability to absorb light
• What is the role of light in photosynthesis?


  It provides the energy needed for the process
• What happens to the rate of photosynthesis as light intensity increases?


  It increases steadily up to a certain point
• What occurs when light intensity exceeds a certain level in photosynthesis?


  The rate of photosynthesis no longer increases
• How can you change the light intensity in a lab experiment?


  By moving a lamp closer to or further away from the plant
• What is required to obtain a proper graph of the rate of photosynthesis against light intensity?


  You need to measure the light intensity at the plant using a light meter
• What is one raw material needed for photosynthesis?

  CO₂
• What happens to the rate of photosynthesis as CO₂ concentration increases?


  It increases up to a point, after which it levels off
• What indicates that CO₂ is no longer the limiting factor in photosynthesis?


  When the graph of the rate of photosynthesis levels off as CO₂ increases
• What is the effect of temperature on the enzymes involved in photosynthesis?


  Temperature affects the rate at which enzymes work
• What happens to enzymes involved in photosynthesis at high temperatures?


  They can be damaged, affecting the rate of photosynthesis
• At what temperature do enzymes involved in photosynthesis typically get damaged?


  About 45 °C
• What should you understand about graphs showing limiting factors in photosynthesis?


  • They can show the effect of multiple limiting factors.
  • The rate of photosynthesis increases with light intensity until a limiting factor is reached.
  • Different lines on the graph can indicate different limiting factors based on their levels.
• What does it mean when a graph levels off in relation to limiting factors?


  It indicates that the factor being measured is no longer limiting the rate of photosynthesis
• How can you determine which factor is limiting photosynthesis from a graph?


  By observing which line levels off first and at what point
• What should you be prepared to do in an exam regarding graphs of limiting factors?


  Describe what is happening in the graph