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Experiment to investigate the effect of different concentrations of Carbon Dioxide on the rate of photosynthesis.

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Experiment to investigate the effect of different concentrations of Carbon Dioxide on the rate of photosynthesis. Introduction Photosynthesis is the main source of energy in all plants and by this route supplies energy to the whole ecosystem. Photosynthesis is a plant's way of creating food, the plant takes in carbon dioxide and water and using light energy (usually from the sun) the plant converts the carbon dioxide and water into glucose and oxygen. Light + chlorophyll [image001.gif] 6CO[2] + 6H[2]0 C[6]H[12]O[6] + 6O[2] carbon dioxide + water sugar + oxygen The equation above shows the overall action of photosynthesis but represents the total of a number of different reactions going on. Photosynthesis takes place mainly in the leaves of a plant. Leaves are a good location for photosynthesis to take place because they have a large surface area for light absorption. Leaves are also thin allowing easy gas diffusion in and out of the leaf and the vein system supports the leaf and provides a way of carrying substances to and from all the cells in the plant. The chloroplasts within the leaf cells contain chlorophyll. This substance gives the leaves their green colour and absorbs the sunlight providing energy for the photosynthesis. Limiting factors Light can limit the rate of photosynthesis even if carbon dioxide and water are both present; a maximum rate of photosynthesis is reached at a certain light intensity. ...read more.


Water can also be a limiting factor but the same volume of solution was used each time and water is probably never a limiting factor for a water plant. Obtaining A measuring cylinder was used to make the dilutions of sodium hydrogen carbonate accurately and to conduct the experiment in the same volume of solution each time. A thermometer was used to record the temperature of the water to make sure that it was not heating up too much from the heat of the lamp. A stopwatch was used to measure the 2 minutes for the plant and solution to settle before a reading was taken. It was also used to time the one minute bubble recording time accurately. The lamp was set at 5 cm from the measuring cylinder because a distance of 5 cm was found to give a good rate of photosynthesis in a preliminary experiment. This distance was checked at the start of each experiment. Results: Temperature and bubble count readings at each dilution of sodium hydrogen carbonate NaHCO[3]% Initial water temperature (�C) Final water temperature (�C) Number of bubbles/min (1) Number of bubbles/min (2) Average number of bubbles/min 50 27 28 0 0 0 60 28 29 6 4 5 70 24 27 23 27 25 80 26 29 27 22 24 90 26 28 51 66 58 100 25 28 69 71 70 The average was found by adding the two sets of results and dividing the answer by 2. ...read more.


This variation could have been reduced if the volume of oxygen given off could have been measured, by collection in a graduated tube, thus difference in bubble size would not have mattered. � Both readings for a given concentration of sodium hydrogen carbonate solution were made from the same dilution. The second reading was therefore made when the solution had already provided some carbon dioxide for photosynthesis during the first reading. Each reading at a given concentration of sodium hydrogen carbonate solution could have been done with a freshly made up dilution to ensure that the starting concentration of carbon dioxide available was the same. � Calcium carbonate was deposited on the Elodea because distilled water was not used to make the sodium hydrogen carbonate dilutions. Use of distilled water would avoid this problem. An improvement to the experiment would have been to collect some of the gas released and test it to check that it was oxygen. When collected into an upturned test tube the gas should have relit a glowing splint. The effect of carbon dioxide concentration on the rate of photosynthesis could also have been studied at different light intensities and temperatures. A different water plant could be used. It would have be put in water otherwise the oxygen bubbles could not be counted or collected. Books referred to: Biology by DG Mackean Biology for you by Gareth Williams The Penguin Dictionary of Biology A New Introduction to Biology by B. Indge, M. Rowland, M. Baker Internet site: Learn.co. ...read more.

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