The 2015 Hermitage Schools Plant Science Competition was centred on photosynthesis, and had seven experiments to do with plant growth and sunlight. For those interested, the instructions are very detailed and contain many interesting experiments.
My entry looked at the effect of sunlight on the rate of photosynthesis, and the effect of sunlight on the carbonic acid content of water. I also conducted a research project on the three types of photosynthesis (C3, C4 and CAM), why the different processes result in different rates of growth and water use, and the prospect of artificially improving the process of photosynthesis. My logbook is available here. The abstract and key results from my two experiments are listed below.
For my experimental write-up and research project, I received runner-up for the Paul Johnston Memorial for Senior Science Award.
Production of Oxygen in the Process of Photosynthesis
This experiment studied whether oxygen is a product of photosynthesis. Waterweed was sealed in a test tube containing carbonated water. The formation of bubbles indicated the production of a gas, most probably oxygen, as a by-product of photosynthesis. Although some bubbles were formed in the test tubes placed in the dark, many more bubbles formed in the test tubes exposed to light, confirming the hypothesis that the process of photosynthesis produces oxygen.
Volume of Gas Produced in a Test Tube of Waterweed Against Time
Intake of Carbon Dioxide in the Process of Photosynthesis
Waterweed was placed in sealed test tubes containing bromothymol blue indicator in water that had carbon dioxide dissolved in it. The colour of the solution indicated the pH, and therefore how much carbon dioxide was dissolved. The results showed that carbon dioxide was consumed by the waterweed much more rapidly when the waterweed was exposed to sunlight. The results also indicated that a blue filter did not have a major effect on the photosynthetic rates. A surprising outcome was the minor consumption of carbon dioxide by the waterweed in the dark. This was attributed to the second (light independent) stage of photosynthesis occurring.
For more information on the 2017 Hermitage Plants Schools Competition, see this post.