How carbon dioxide can affect the rate of photosynthesis

Aim: To investigate how carbon dioxide can affect the rate of photosynthesis.

Hypothesis: The rate of photosynthesis in the water plant hydrilla will change as the rate of carbon dioxide changes.

Background information: Photosynthesis

Photosynthesis is the process of autotrophs turning carbon dioxide and water into carbohydrates and oxygen, using light energy from sunlight. Autotrophs are organisms that are able to produce nutrients and organic compounds using inorganic materials. Examples of autotrophs are green plants, algae, bacteria, etc. Organisms which are capable to photosynthesize are called photoautotroph. The chloroplasts (plant cell that contains chlorophyll) in autotrophs trap light energy from the sun and use it to combine carbon dioxide with split water to make food for themselves which are in the form of sugar, glucose, etc. Glucose in plants is made into a variety of molecules and chemicals to support its needs. Plant cells which contain complex chemical pathways add nitrogen and sulphur to produce amino acids and then protein. Plants make up their own cell membranes by rearranging carbon, oxygen, hydrogen and by adding phosphorus. We absorb chemicals produced by plants even though we can produce most of the chemicals we need because some chemicals like amino acids can only be obtained from plants. This shows that plants are crucial for animals as they are depended on it. Another function of photosynthesis is the waste product of the process is oxygen. Photoautotrophs transform carbon dioxide to oxygen when photosynthesizing. This is essential for life because oxygen is an important element for respiration which is performed by both autotrophs and animals.

Photosynthesis can ne summarized as the following formu...

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...sed, the stopwatch has to be reset and both classmates have to prepare for the next trial. These may only cost a few seconds but during these few second (time gap) the stem of the hydrilla has continued to release bubbles which we haven’t counted them which can affect the data because fewer bubbles were counted. We can improve next time by asking more people to help us with the timing. For example, after 1 minute when the 1st trial finishes, one student stops his/her stopwatch and simultaneously another student starts his/her stopwatch simultaneously. There is also an error shown in the graph. The mean of rate of bubbles per minute is expected to have a continuous increase but it decreases 0.33g starting from 8.0g to 10g. The results may not be accurate due to this. I can improve next time by conducting the experiment for several times until I get the relevant data.