What is the effect of population density of plants on the rate of photosynthesis? By: Adam Harvey, Emerson Perry, Alex Palmer, and Spencer Olson

Goal The goal of our experiment was to see the effects of different population densities (number of plants in a given area) on overall growth and photosynthesis. Also we wanted to see if different species of plants would handle resource deprivation differently.

Hypothesis In our experiment, we predict that population density will most certainly have an affect on the rate of photosynthesis. We believe that the competition for resources will cause the plants overall health and growth to suffer. There will be a direct relationship between the number of plants in the same pot and the rate of photosynthesis. The more plants in the pot, the less healthy those plants will be. Also we believe that different species will handle resource deprivation better when living together.

Research In researching our topic, we found another experiment posted online that was very similar to ours. The group concluded that there was weak to no correlation between population density and plant growth (photosynthesis). We also found that Charles Darwin believed that similar organisms would grow the worst together because they would be competing for the same resources needed for their growth.

Design Our experiment had 7 plant containers with 2 different species of plants. 1 planter with 2 Wisconsin Fast Plant species growing together 1 planter with 2 Lilliput Zinnia species growing together 1 planter with 4 Wisconsin Fast Plant species growing together 1 planter with 4 Lilliput Zinnia species growing together 1 planter with 8 Wisconsin Fast Plant species growing together 1 planter with 8 Lilliput Zinnia species growing together 1 planter with 4 Wisconsin Fast Plants and 4 Lilliput Zinnia growing together

Summary of Procedure Each of the cups was observed for a few weeks and at the end we measured the rate of photosynthesis and observed the overall health and growth of each plant. We then reached our conclusion based on our data provided in the next slide……………….

Results…

Statistics for fast plants For our stats we ran an F-test in excel. Our f critical value comparing all of the fastplant groups was Our actual F value was In order to reject the null hypothesis, our F value must be below Therefore we are concluding that there is not a big enough difference for there to be a correlation between population density and rate of photosynthesis.

Stats for Zinnias For the Zinnia groups, we had an F-Critical value of 3.12 and an actual F value of Therefore we cannot reject the null hypothesis since our F value is not lower than We concluded for this group that there is no correlation between population density and rate of photosynthesis.

Qualitative Data The plants in the planter that contained more plants in it looked whiter, and droopier. The plants in the planter with only one other plant looked greener.

Quantitative Data Contradicting our qualitative data, the plants that grew with a higher population density, had a faster rate of photosynthesis. This was very odd to us but we have some reasons for error on the next slide that could possibly explain why our hypothesis was wrong.

Reasons for error The first reason for error is simply over watering. We may have given the plants too much water causing the plants with a higher population density, to grow better. Also we had a very small sample size and therefore, if one of the seeds was bad in a particular container, it would throw off the results for that group. Had we done the experiment again, a much larger sample size would have been used.

Conclusion Based on our initial thoughts, we thought that there was a correlation between population density and rate of photosynthesis. However, after running our stats in excel we found that this was not the case. In conclusion, there is no correlation between population density and rate of photosynthesis for our experiment.