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An Investigation into the Rate of Photosynthesis.

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An Investigation into the Rate of Photosynthesis Aim The aim of this investigation is to determine how sunlight affects the amount of oxygen produced during photosynthesis, therefore investigating the rate of photosynthesis Plan For all green plants, it is essential to produce their own food. The process by which they do this is called photosynthesis. During photosynthesis plants produce the sugar, glucose. This, as well as various other chemicals absorbed through the roots, is then used as raw materials in the manufacture of all the substances which form a plant. For photosynthesis to take place, sunlight energy is required. This energy is absorbed by chlorophyll in the plant. This is a found in small green pigments in the leaf called chloroplasts. This energy then combines with water molecules (from the soil) and carbon dioxide (from the air). This reaction takes place to produce glucose, and oxygen, which is released into the air as a waste product. The equation for to show this is as follows: 6CO2 + 12H2O C6H12O6 + 6O2 + 6H2O Light and chlorophyll Cells in plants are specially adapted to aid with photosynthesis. Factors The rate of photosynthesis can be affected by various factors including light intensity, temperature, accessibility of water, and availability of nutrients. If the conditions that the plant requires are improved, the rate of the reaction should increase. Therefore, one factor is to be considered is temperature. Increasing the temperature from, for example, 15 degrees to 30 degrees could increase the rate of photosynthesis, possibly doubling it. ...read more.


It must be set down firmly in place with a paper clip, upside down in the test tube, as leaves have a greater number of stomata on the underside of their leaves, so gas will be released more readily. I will set up the desk lamp 15 cm away from the pondweed and every time I will move it 5cm further away measuring the distance with a meter ruler. Then I will turn on the desk lamp and start the stop watch, and immediately begin counting the bubbles for 1 minute. After recording my results, showing distance in cm and number of bubbles I will repeat the experiment for distance 25 cm, and then do the same with distances of 20, 25, 30, 35, 40, 45, 50 cm. Carrying Out I had no problems during my experiment. To ensure that it was a fair test I was carrying out I did the experiment all together, instead of carrying it out over for example 2 days. This ensured that the conditions were relatively the same throughout. I also used the same piece of pondweed throughout. This was important because the size and surface area of the leaves on the pondweed could have changed on a different piece of pondweed and therefore would have altered the result. To overcome this problem I could have weighed the different pieces of pondweed and made sure they were the same weight, but this wouldn't have been totally accurate. Therefore using the same piece throughout was the best decision. I always counted the bubbles given off from the pondweed for the same amount of time (1 minute), and also every ...read more.


This would certainly be more reliable. Had no anomalous results, but if there were there are several reasons why it could be. Firstly, I could have miscounted the bubbles. Also the pondweed might not have been producing oxygen as properly due to an airlock I did not notice. Furthermore, lots of people were crowded in the same room carrying out the experiment. Now I can't be certain that the position of my equipment remained the same as it is possible that part of the apparatus could have been moved. To overcome this problem I could have used chalk to mark the position of everything. In addition, with the curtains open, extra light from the windows or other experiments could have easily affected the rate of photosynthesis. Also, as I did each repeat, the pondweed most likely gained heat energy affecting the rate of photosynthesis. To develop and extend my experiment there are several different tests for photosynthesis I could carry out. The first test I could do is to put a piece of foil on a destarched leaf and leave the plant in the sun for three days. Then test the leaf for starch using iodine. If it turns blue-black there is starch present. The second is to test for chlorophyll. I would take a variegated leaf (one with white and green leaves) and test it for starch, remembering that only green parts of plants contain chlorophyll. The last is to leave a destarched leaf in a plastic bag that contains soda, lime, and crystals for three days. This would absorb carbon dioxide and so there should be no carbon dioxide for the plant to use. Also next time I would do more repeats to make my results more accurate. ...read more.

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