The Effect of Concentration of CO2 on the Average Rate of Photosynthesis in Spinach Leaf Disks

摘要

The purpose of this experiment was to determine the effect of carbon dioxide concentration on the rate of photosynthesis in spinach leaves. Small circular disks were cut out of the spinach leaves using a standard hole puncher. Then solutions of differing concentrations of carbon dioxide, 0.2%, 0.4%, 0.6%, 0.8%, and 1.0%, were all prepared, and each solution was spread equally among five cups. There was also a control solution that contained only water. Any gases within the leaves were then sucked with a syringe, using a specific technique to create a vacuum. For each solution of differing carbon dioxide concentration, there were five cups of solution with ten leaf disks per cup, so there was a total of 50 leaf disks per concentration. The cups were then exposed to light for 20 minutes, and the number of disks floating in each cup was measured every minute. Results were calculating by finding the ET50 for each concentration. The ET50 is the time it takes for 50% of the leaf disks to float and is a good indicator of the rate of photosynthesis. It was hypothesized that if the concentration of carbon dioxide was increased, then the rate at which photosynthesis occurs will also increase. The null hypothesis was that the concentration of carbon dioxide will have no effect on the rate of photosynthesis. The results of the experiment supported the hypothesis. So, the experiment suggests that there is a direct relationship between CO2 concentration and the rate of photosynthesis.