Explain the limiting factors of photosynthesis using the provided graph showing CO2 exchange over a 24-hour period.

here are the answers to your questions:

2.2.1

• A) Independent variable: Light intensity
• B) Dependent variable: Carbon dioxide exchange (or Rate of photosynthesis)

2.2.2
The two factors limiting the rate of photosynthesis in the experiment are:

• Light intensity
• Carbon dioxide concentration

2.2.3

• A) Point W to X
  • Time of day: Night / Early morning (before sunrise)
  • Explanation: During this period, there is no light or very low light intensity. Photosynthesis cannot occur or is very slow. However, the plant is still respiring, releasing carbon dioxide, leading to a net release of carbon dioxide.
• B) Points Y to Z
  • Time of day: Midday / Peak sunlight hours
  • Explanation: During this period, light intensity is high, allowing for a high rate of photosynthesis. However, the rate has plateaued, indicating that another factor, such as carbon dioxide concentration or temperature, has become limiting, preventing further increase in the rate of photosynthesis.

2.2.4
The flattening of the graph at points Y and Z signifies that the rate of photosynthesis has reached its maximum under the given conditions. At this stage, light intensity is no longer the limiting factor. Instead, another factor, most likely the concentration of carbon dioxide or the prevailing temperature, is restricting any further increase in the rate of photosynthesis, even if light intensity continues to rise.