Q: How Do Plants Exercise? A: They Photosynthesize

Plants use light sources to gain energy for photosynthesis. The amount of energy exerted by the plant to preform photosynthesis is directly related to how much it respires such as how breathing becomes heavier after physical activity. In order to visualize this process, you will need:

·       1 250mL graduated cylinder

·       Distilled water

·       Aquatic plant (Cabomba)

·       Scissors

·       Dissecting needle

·       Light source such as a lamp

·       Timer

To prep for the experiment, take one sprig of the Cabomba plant and carefully flatten its fronds against its stem. Fill the graduated cylinder with 200mL of distilled water. With adult supervision, poke holes along the stem using a dissecting needle and cut the bottom of the stem using scissors at an angle. Immediately place the sprig in the graduated cylinder with the freshly cut end at the top. Make sure the entire plant is completely underwater. Place the plant 15 centimeters from the light source for five minutes to equilibrate the photosynthesis process. Then count the number of bubbles released by the plant for 30 seconds. Record the data and repeat two more times at the same distance. After you have recorded three data points for the distance of 15 centimeters. Move the plant 10 additional centimeters away from the light source so that it is a total of 25 centimeters away from the light source. Let the plant equilibrate for five minutes the repeat the 30 second intervals of bubble counting for three trials while recording each data set. After those three data points are recorded move the plant another 15 centimeters so that it is a total of 45 centimeters away from the light source. Once again, leave the plant to equilibrate for five minutes and then count the amount of bubbles produced by the plant over the course of 30 seconds for three data points. After you have three data points each for each distance, compile the data in a table such as Table 1 below which represents my data during this same experiment.

It is important to note that the light source is the control variable, the plants distance from the light source is the input variable, and the number of bubbles produced is the output variable. As shown by the table, the farther away the plant was placed from the light source the amount of bubbles produced decreased. Similarly, the closer the plants are to the light source the better it preforms photosynthesis. Based on this logic, the more efficient the plant is at photosynthesis the more it respires oxygen into the water. Photosynthesis takes energy from the plant such as exercise does a person. People use less energy walking so there breathing is normal, but once the person begins running, their breathing becomes heavier in order to obtain enough oxygen for their muscles. Plants at the 40 centimeter mark can be compared to the walking person. It is undergoing exercise during photosynthesis but it is not very intense. The 25 centimeter mark can be compared to jogging in which the intensity becomes more difficult than walking but not as intense as running. When the plant was placed at the 15 centimeter mark, its job became a sprint and required more energy so the plant respired more than the other two distance marks. 

The results I obtained were rather consistent in bubble production and support my hypothesis that increased distance from the light source would result in a decrease of bubble production. To better my personal results, more than one person should count the bubbles being released during the time trials to improve accuracy. To fuller quantify the amount of oxygen respired by the plant, the graduated cylinder could be sealed and measure the original air pressure. After each 5 minute timer, the air pressure could be measured at each distance. Using the density of oxygen, we can use the change in pressure to determine how much oxygen is actually released at each distance. I also predict that there will be an increase in bubble production if the light source’s power is increased due to an increased efficiency in photosynthesis.