Question

estions to consider: 1. How do the three different light levels affect the rate of photosynthesis in C3 plants? a. In C4 plants? eins 2. Were the photosynthetic rates different between C3 and C4 plants? illa. Was this more dramatic at any of the light levels? 3. You did not use temperature as a variable in any of your analyses but you still collected data on it. Why is it still important to monitor the temperature? 4. Recall CAM plants from BIOL 141. How would a CAM plant behave differently if we had used it in this experiment?

Answer 1

1. When a plant is exposed to dim light, the rate of photosynthesis in the plant will be low due to less light availability and less energy reaching the leaves. With increasing light intensity, the rate of photosynthesis increases as we see in an aquatic plant under laboratory conditions. We can see more O2 bubbles evolving with increasing light.But after some rise in the rate, it remains constant. The rate of photosynthesis reaching steady state is observed both in C3 and C4 plants.

In case of C3 plants the increase in the Co2 fixation is less compared to C4 plants as the temperature rises. Increase is in temperature is much more beneficial to C4 plants than to C3 plants

In C4 plants the rise in the CO2 fixation or photosynthesis is almost double that of the C3 plants.

2. The photosynthetic rates are different for C3 and C4 plants. At higher temperature, the increase in photosynthetic rates in C4 plants are much more than C3 plants. There is sudden rise in the rate of photosynthesis in C4 plants at higher temperature.

3. Whenever an experiment is used, we keep the other variables constant and only change the variable that we would like to study. So it is important to record the temperature. When the light intensity is very high, temperature may also be high and plant enzymes may not work properly at that temperature that are required for photosynthesis. So to observe that the temperature is not reaching such levels in the plant, it is important to keep the temperature recorded in both plants C3 and C4. Also to see that the observations we are making is not due to any differences in temperature.