PlantingScience: The Rate of Photosynthesis By: Andy Blake, Sophia Lo, and Melissa Mikalsen

Question: How does the rate of photosynthesis differ within different plants?

Hypothesis: Different species of plants will have different rates of photosynthesis. If a plant is a darker green, then it should photosynthesize faster because the plant contains more chloroplasts and thus has more chlorophyll, one of the key components for photosynthesis.

Experimental Control ❖ The experimental control was the different species of plants used: Dieffenbachia, Red Chard, Spinach, and Romaine Lettuce

Procedure 1.Select four plants (in this experiment, the plants included Dieffenbachia, Red Chard, Spinach, and Romaine Lettuce) and make 10 leaf disks for each plant. 2.Fill 4 cups halfway with water and add a pinch of baking soda and a drop of soap. Carefully mix it together; the soap should not foam. 3.Using a syringe, sink the leaf disks by placing the leaf disks into the syringe and filling the syringe about ⅓ of the way using the mixture of water, soap, and baking soda. Then, place your thumb at the bottom of the syringe and pull, creating a vacuum to sink the disks.

Procedure cont. 4. Repeat Step 3 for each of the plants. Once you have sunk the disks for one plant, place the disks into one of the four cups. 5. After all the leaf disks have sank, place all four cups under a lamp. 6. Record how many leaf disks have floated up every minute and record the data in a chart.

Quantitative Data: Number of Leaf Disks Floating per Minute Time (minutes) Leaf Disks Floating: Dieffenba chia Disks Floating: Red Chard Disks Floating: Spinach Disks Floating: Romaine Lettuce

Quantitative Data cont. Time (minutes) Leaf Disks Floating: Dieffenba chia Disks Floating: Red Chard Disks Floating: Spinach Disks Floating: Romaine Lettuce

Quantitative Data cont. Time (minutes) Leaf Disks Floating: Dieffenba chia Disks Floating: Red Chard Disks Floating: Spinach Disks Floating: Romaine Lettuce

The Rate of Photosynthesis in Different Plants

Analysis of Data ❖ The graph and data table show that spinach has the fastest rate of photosynthesis because photosynthesis had occurred in all 10 leaves within 5 minutes. ❖ Romaine Lettuce and Red Chard had similar rates of photosynthesis because both the Romaine lettuce and Red Chard showed a similar trend on the graph. ❖ Romaine lettuce has a faster rate of photosynthesis at the beginning, but a higher number of Red Chard disks photosynthesized at the end of the experiment.

Analysis of Data cont. ❖ Dieffenbachia had the slowest rate of change, with only 5 disks which had photosynthesized. ❖ The data were consistent; there were no unusual data points, although dieffenbachia was expected to photosynthesize more quickly, but because it is an indoor plant, it may not need as much light to grow.

Possible Errors ❖ Some of the cups could have been exposed to more light than the others. This is due to some of the cups being closer to the edge of the lamp. ❖ One of the spinach disks rose before it was placed under the light. This is because the spinach disks were sunk first.

Effect of Error on Data ❖ Since some of the cups could have been exposed to more light than the others, there disks would have photosynthesized at a higher rate. ❖ Since one of the spinach disks rose before it was placed under the light, most of the other plant disks were also photosynthesizing before being timed.

Conclusion The hypothesis stated that greener and darker plants would be able to photosynthesize more quickly, and this was somewhat correct. The plant that was able to photosynthesize the fastest was spinach, which was a darker green and had less vein in the leaves than the romaine lettuce and the red chard. It was not, however, as dark as the dieffenbachia, which had dark green and some white coloring, and the dieffenbachia was the slowest photosynthesizing plant.

Conclusion cont. With the exception of dieffenbachia, the darker plants with less veins were able to photosynthesis faster. One way to explain why dieffenbachia had a slower rate of photosynthesis could be that it is an indoor plant and does not require as much sunlight while spinach is a plant that grows best when fully exposed to the sun, so different species of plants do have different rates of photosynthesis which may depend on its color, the amount of veins in the leaves, and where it is grown.