For each of the three experiments, identify the limiting factor for photosynthesis and explain why, using the provided graph and experimental conditions.

Here's the analysis for question 1.1.8:

To identify the limiting factor for each experiment, we need to compare the conditions and the resulting curves on the graph. A limiting factor is the variable that restricts the rate of photosynthesis.

• Experiment 1 (Curve 1):

  • Conditions: Temperature = $30\,^\circ\text{C}$, $\text{CO}_2$ = $0.13\%$.
  • The problem states "Experiment 1 measured the effect of light intensity on photosynthesis".
  • On the graph, curve 1 shows that as light intensity increases, the rate of photosynthesis increases significantly before leveling off. At lower light intensities, the rate is directly proportional to light intensity, indicating that light intensity is the limiting factor.

• Experiment 2 (Curve 2):

  • Conditions: Temperature = $20\,^\circ\text{C}$, $\text{CO}_2$ = $0.13\%$.
  • The problem states "Experiment 2 measured the effect of temperature on photosynthesis".
  • Comparing curve 2 to curve 1, the $\text{CO}_2$ concentration is the same, but the temperature is lower ($20\,^\circ\text{C}$ vs $30\,^\circ\text{C}$). Curve 2 shows a lower overall rate of photosynthesis than curve 1, even at high light intensities. This indicates that the lower temperature is limiting the maximum rate of photosynthesis.

• Experiment 3 (Curve 3):

  • Conditions: Temperature = $30\,^\circ\text{C}$, $\text{CO}_2$ = $0.03\%$.
  • The problem states "Experiment 3 measured the effect of carbon dioxide on photosynthesis".
  • Comparing curve 3 to curve 1, the temperature is the same, but the $\text{CO}_2$ concentration is much lower ($0.03\%$ vs $0.13\%$). Curve 3 shows a significantly lower overall rate of photosynthesis than curve 1, even at high light intensities. This indicates that the lower carbon dioxide concentration is limiting the maximum rate of photosynthesis.

Based on this analysis:

• Experiment 1: Light intensity
• Experiment 2: Temperature
• Experiment 3: Carbon dioxide concentration

This matches option C.

C) 1: light intensity, 2: temperature, 3: carbon dioxide concentration