Factors The Rate Of Photosynthesis example essay topic

Photosynthesis investigation Spot skill, Analysis and Evaluation Aim To investigate the effect changing the level of light has on the rate of photosynthesis. What is photosynthesis? Photosynthesis is the process through which light energy, water, and carbon dioxide are converted to carbohydrate and oxygen in the presence of chlorophyll. Photosynthesis takes place in the leaves.

Photosynthesis needs all the factors to work steadily, if we limit one of these factors the rate of photosynthesis will decrease. To prove this we are going to try investigating it on pondweed and limiting the amount of light it gets and seeing what the rate is and how it changes. For photosynthesis to work effectively it needs: o carbon dioxide o water o light energy o chlorophyll The carbon dioxide comes into the plant from the air in the atmosphere, whereas the water is absorbed by the root system and then travels up the stem through the transpiration system to the leaves. The light energy is absorbed from the sun through the leaves. This picture explains where the sunlight is absorbed in the leaf: The main job of the leaf is to get light energy from the sun. It has a flat surface which provides a large surface area for the absorption of light energy from the sun.

These are the word and chemical equations for photosynthesis: (Above is the word equation for photosynthesis and below is the chemical equation) 6 CO 2 + 12 H 2 O + light energy -- - C 6 H 12 O 6 + 6 O 2 + 6 H 2 O Limiting factors Three factors limit photosynthesis from going any faster. Light Sometimes light is a limiting factor. A plant may have lots of water and carbon dioxide, but it will not photosynthesise very fast if there is not enough light; increasing the light intensity will make photosynthesis faster. This is what we are going to investigate. This shows that as the light is increased the arte of photosynthesis increases to a certain extent then slows down and eventually stops. Carbon dioxide Sometimes the level of carbon dioxide is limiting.

There may be plenty of light but the plant cannot photosynthesise because it has run out of carbon dioxide. The amount of water available to the plant will affect the rate of photosynthesis. If the plant does not have enough water, the plant's stomata will shut and the plant will be deprived of CO^2. Temperature Temperature can be a limiting factor too. The rate of photosynthesis will be limited if it is too cold for the enzymes to work properly. An increase in temperature usually increases the rate of photosynthesis.

But at 40 degrees the rate slows. At temperatures above this, the rate drops quickly. This is because the enzymes in photosynthesis are being destroyed. Because in our experiment we are limiting the light intensity, we have to make sure that these two factors stay the same and equal throughout the experiment to make it a fair test. As you can see from the results they were mainly the same throughout the investigation and you could usually see a pattern in the results but there were two anomalous results, these were in test number 1 at 25 cm and the second at test number 2 at 15 cm. in the first one the other two results were 13 and 9, these are quite close together but with the results from the first one the averages will be different and make it not fit.

This is the same as the second one; while the other two are 26 cm and 32 cm this one is 10 cm. It makes the averages odd. These anomalous results could have been because there was a change in one of the limiting factors. For example it may have been that the light was very hot and the heart increased the rate of photosynthesis for those two, or the results were recorded wrongly. Below, I have put them into a graph and drawn the line of best fit. The graph shows that the length of the oxygen bubble in the capillary tube gets smaller when the lamp is moved further away.

This means that the further away the light is the less oxygen is being produced which means the rate of photosynthesis is decreasing as the lamp goes further away. I have found that my results are not completely accurate. This may be because of varied conditions or they may have been recorded wrongly. I have noticed that the 2nd set of results is a lot different to the other two. This may have been the reason why some of the averages were odd. I have also noticed the less distance between the lamp and the source the longer the length of the oxygen bubble.

This happens because the more light the plant has the higher the rate of photosynthesis will be. Evaluation I think that the method that was used was probably the best way to collect the information. I also think that this experiment was a fair one. This is because each time the light was moved further away from the plant it was kept on for equal amounts of time and was also given the same amount of time to cool down.

I think that the results were mainly accurate. The bubbles were measured in MM so it was quite a small scale giving detailed results. Also the test was quite reliable because at each 5 cm the rate of photosynthesis was being measured 3 times making the results more reliable. Most of these repeats were reliable because they had almost the same outcome. Every time this was done the results gained were fairly similar proving the accuracy.

The only factor that was limited was light, because we gave the plant plenty of water and carbon dioxide (in the solution) we could find out if only one limiting factor needed for photosynthesis was effective. However we did find some anomalous result, mainly in the test 2 but others as well. For example in test one where the lamp was 20 cm the result is very out of place according to the other two times it was tested at this distance. This may be because it was the first one recorded so the plant got a lot of light at once or maybe because the heat of the lamp affected the rate of photosynthesis. To stop this from happening in further investigations like this a Perspex screen could have been placed between the light and the syringe to reduce any heating effect that the light may have. Also in the 15 cm column there is one anomalous result.

Two are round about 30 mm long and one is only 10 mm. These odd results may have occurred because the lamp was not given enough time to cool down and because the bulb was being switched on and off constantly every 5 minutes or so. This may have affected its light making it brighter or dimmer. If we had to do this experiment again I would use a more powerful lamp or torch with a straight line beam to improve it. This would be more effective because the light would mainly hit the plant and not light the entire dimly lit room. Using the same piece of pondweed for each experiment was impractical as the weed's photosynthesis rate decreased over time.

But using a different piece of weed for each experiment did create the problem of it being impossible for each piece to have the same surface area making the test unfair..