Photosynthesis Lab

June 5 2016


In our lab we used a Cabomba plant to see if light intensity will affect the rate of photosynthesis. In order to do this experiment we needed a cabomba plant, a beaker, parafin, a ruler/meter stick and a lamp. When the experiment was conducted we placed the beaker which was filled with water and had the cabomba plant placed inside at the end of the meter stick and we called that loaction 0 cm. At 0 cm we shinned the light at the beaker and counted the amount of bubbles we saw as this was oxygen (product of photosynthesis). After 1 minuted we moved it back 5 cm each time until we reahced 20 cm


Looking at the lab we noticed that the closer the light was to the beaker the rate of photosynthesis increased as there were more bubbles being released whereas when the light was further away from the beaker rate of photosynthesis decreased because less bubbles were being released. This change happened because photosynthesis is based on 2 parts, light dependent and light independent reaction. What was impacted during the experiment is the light dependent reaction as this reactions limiting factor is the amount of light or the light intensity. Even though if we graph rate of photosynthesis and light intensity it is a directly proportional (straight line) relationship. Rate of photosynthesis lowers because in the light independent reaction 18 ATP and 12 NADPH is needed and these comes from the light dependent reaction. During the light reaction as light falls upon the leaf, ATP is made via the ATP synthase pumping hydrogen ions and NADPH is made in the NADPH reductase when NADP plus gets oxidized into NADPH. This process speeds up as when more light falls upon the leaf and gets slowed down when there is less light falling upon the leaf.

Difficulties in Preparing the Lab

Some of the notable difficulties in preparing this lab is firstly the fact that this is the first time I ever prepared my own lab. This is a difficulty because throughout all my science classes the teacher normally assigned us the lab with the materials list and procedures but this was the first time we had to come up with one. The first problem was determining the purpose of the lab or what we had to measure or calculate and we chose to see how light intensity affects the rate of photosynthesis. The second problem was determining the best procedure so that we can get maximum results. In order to do this we used a pro-pro chart and this presented another problem because throughout high school I used a pro-con chart to contrast between a certain thing rater than compare to very similar things in order to get a better outcome. The last problem I encountered was choosing what plant to use in order to get the best results. I ended up choosing to use the cabomba plant to get the best results because some of the other plants needed more time to able to photosynthesize and time wasn't wasn't our friend for this lab

What changes would you make to the lab procedure in the future?

After the creating the best possible lab procedure from multiple websites and links there are still some minor changes that could have been done, and which we did, to make the lab better. An example of this was the use of baking soda. This is because during the lab before we used baking soda we noticed that we very getting very minimal results and we couldn't see the trend of how light intensity affects photosynthesis. When we put some baking soda into the beaker with water and the plant we noticed more bubbles being released which meant photosynthesis was happening. Also this changed helped our lab because when we moved the lamp further back we noticed that less bubbles were being released. Baking soda really helped because soda is sodium bicarbonate. When adding the baking soda we gave the cabomba plant extra carbon so it would increase the amount of carbon (reactant).


Rate of Photosynthesis: Limiting Factors. (n.d.). Retrieved June 5, 2016, from of photosynthesis limiting factors.pdf