What Affects The Rate Of Photosynthesis?

                       Light + chlorophyll

6CO2 + 6H2O          ⇛          C6H12O6 + 6O2

Carbon   + Water    ⇛          Glucose    + Oxygen      

Dioxide

Prediction:

1. The factors I think that will affect the rate of photosynthesis are light, temperature, water and carbon dioxide. I predict that the temperature will affect the rate of photosynthesis in two ways. Firstly if you increase the temperature the rate of photosynthesis will also increase, but it will increase to a certain point and that is when there is a limiting factor. But if you increase it too much, the enzyme will be denatured. On the other hand if you decrease the temperature, it will also decrease the rate of photosynthesis. If the temperature is increased by 10°C, it will double the rate of photosynthesis.

Prediction:

2. The amount of CO2 will also affect the rate of photosynthesis. Increasing the amount of CO2 will affect the rate of photosynthesis by taking it into the leaf and diffusing it. I think that the experiment should not take more than to hours so that excess amount of light doesn’t get in.

Prediction:

3. All plants need water for the process of photosynthesis and if there isn’t enough of it the rate of photosynthesis will slow down rapidly.  When the plant lacks water, the stomata closes, it also closes when the plant lacks CO2, which means that CO2 is linked with water. The plant makes its food by mixing CO2 and water in the chloroplasts.

Prediction:

4. And finally I predict that increasing the light intensity will also increase the rate of photosynthesis at a continuous scale where light is inversely balanced to distance from light source to plant. This is true to a certain point until another factor is limiting. Pigments in the leaf such as chlorophyll absorb light energy. The leaf doesn’t absorb green or yellow much but reflects them well. If you decrease the amount of light, the rate of photosynthesis will also decrease.

Method:

1. Set up the apparatus as shown on the previous page but leaving out the pondweed, test tube and sodium hydrogen carbonate.
2. Fill half of the beaker with water and put a bit of NaHCO3 (sodium hydrogen carbonate).
3. Get a piece of pondweed and place it in the test tube full of water.
4. Put your finger on top of the test tube and turn it upside down and place it in the beaker.
5. Move your finger away and use the clamp to put the test tube slightly above the base of the beaker.
6. Place the lamp 5cm away from the away from the test tube and switch on the lamp.
7. Record your results.
8. Do this another 2 times so you can get an average for the results
9. Plot the average on the graph.
10. Repeat steps 6, 7, 8 and 9 for the distances of 5cm, 10cm, 20cm and 30cm.

Evaluation: 

Overall, I would say that my experiment was a success since my prediction was supported by my results. This is important in reflection success only if my prediction was sensible and logical. Just as important was where the experiment was not a success and why. The photosynthesis experiment was probably not performed as accurately as it could have been due to some uncontrollable conditions. While performing the experiment, carbon dioxide may have initially limited the rate of photosynthesis.

The negative effects from these problems may be inaccurate data from some readings. These would show up on the graph. However there was only one anomaly. This showed up on the graph, I don’t know what happened but on the distance of 10cm was not in correlation of the graph.

Temperature was a factor controlled by the lamp being used. Even though that the pondweed was in a test tube, that did not stop some of the heat from reaching the plant. The extra heat, however did not affect the temperature of the water.

Conclusion: From the results, which I have gathered, I can state that an increase in light intensity certainly does increase the rate of photosynthesis. When measuring light intensity in terms of distance, the greater the distance, the slower the rate of photosynthesis. While the rate of photosynthesis was decreasing, the rate at which it was decreasing was also decelerating. This is where the line graph decreased. The decreasing of the line graph can be explained by the fact that, light intensity is inversely proportional to the distance. This means that as distance increases, the light intensity decreases at an exceptional rate. If light intensity decreases exceptionally, photosynthetic rates that depend on light intensity also decreases exceptionally. The line graph would eventually reach to ‘0’ where photosynthesis stops as light intensity limits this rate.