Assignment 4

1 .		In the LeafLab, set up an experiment with tomato and set light intensity to 1000 mmol/m2/s. Leave temperature at its default value of 25°C, set gas flow to medium, and use the white light filter. Begin with a CO2 concentration of 0 ppm and continue this experiment by increasing CO2 concentration to 100, 200, 300, and so on, until you reach 1000 ppm. Record CO2 output after each change in CO2 concentration. Plot photosynthetic rate (P) versus C-in and fit a curve to the data. Interpret your plots as follows: Intercept = rate of dark respiration Slope = carboxylation efficiency Asymptote = photosynthetic saturation (maximum rate of photosynthesis) Note your assumptions below.
2 .		Repeat the experiment that you set up in exercise 1; however, use a leaf from corn and set gas flow to high. Plot P versus C-in for both tomato and corn and fit curves to both, then answer the following questions: How does the carboxylation efficiency differ between C3 and C4 plants? How does photosynthetic saturation differ between C3 and C4 plants? Are these differences in photosynthetic saturation consistent with the differences that you observed between C3 and C4 plants in other experiments? Do these differences make sense based on what you know about the anatomy of C3 and C4 plants? Explain your answers.