By James Casieri, Claire Wille, and Evan Kuehnert PLANTING SCIENCE By James Casieri, Claire Wille, and Evan Kuehnert

Question How does the pH of a plant’s environment impact the process of photosynthesis?

Hypothesis We hypothesized that the less drops of acidic or basic compounds added to the  water-soap solution, the faster photosynthesis would occur because in prior experiments with enzymes, the H+ ions in acids and OH- ions in bases interfered with the reaction.

Materials Spinach Leaves Carbonated Water (300mL) Syringe HCl (Acid) NaOH (Base) Soap Water Hole Puncher Timer Beakers (3)

Procedure Gather Materials Create 14 leaf disks for each solution Pour 100mL of carbonated water into each beaker Put enough drops of acid in one beaker to make the solution 4 pH Put enough drops of base in one beaker to make the solution 10 pH Leave the third beaker neutral Add soap to a separate beaker Put 14 leaf disks in the syringe and fill it with the water-soap solution Create a vacuum by placing thumb over the top and pull down for 10 seconds; repeat until all the disks sink Do steps 8 and 9 three times

Procedure (Continued) 11. Put the disks into each beaker, each beaker should receive 14 disks 12. Record number of floating disks every 30 seconds

Control Group Our control group was a neutral (pH 7) solution

Data Time Neutral Acid 0:00 3 0:30 1:00 4 7 1:30 5 11 2:00 12 2:30 6 13 3:00 14 3:30 4:00 8 4:30 9 5:00 9 14 5:30 6:00 6:30 7:00 7:30 8:00 8:30 11 9:00 9:30 10:00

Graph  

Analysis The data clearly demonstrates that the acidic solution is the ideal environment for photosynthesis. The pH of the acidic solution (which was 10) must be either close to or the same as the optimal pH of the spinach plant leaves. After further research, the drastic increase in the speed in which photosynthesis transpired in the acidic solution is because the optimal pH of the enzymes responsible for breaking up electrons in water molecules to create hydrogen ions and oxygen gas must have been at or around the pH of the acidic solution, thus causing the leaf disks to rise faster.

Sources of Error Some leaf disks may have been damaged to the point that they would not float Some leaf disks may have been prepared improperly, causing them to float to the top without the help of photosynthesis. Never could conduct experiment with basic solution, for the NaOH compound reacted to the carbon dioxide in the carbonated water.

Conclusion Based on the results of our experiment, we have concluded that an acidic environment is best for photosynthesis in spinach leaves, contradictory to our hypothesis that a neutral pH would be the ideal environment. However, this is not necessarily the case for all plants; some have an optimal pH higher or lower (more often the latter) than that of the spinach plant. Thus, the results of this experiment do not apply across the board, but rather only pertain to spinach leaves. To sum up, the ideal environment for photosynthesis in spinach leaves is an acidic one.