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How light intensity affects Photosynthesis.

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Introduction

P l a n Photosynthesis is the chemical process, which takes place in every green plant to produce food in the form of glucose. Plants use water and carbon molecules and the suns energy to join together to form glucose, which is sent around the plant to provide food. Cells in the root or stem can use the glucose to make energy, if the plant does not need to use all the glucose immediately then it is stored which is difficult because glucose is hard to store in water. Plants have adapted with this problem by joining hundreds of glucose molecules together to make a starch compound. Starch does not dissolve in water very well so it makes a better food store. Photosynthesis takes the palisade mesophyll cells in the leaf of a plant. It is these cells that contain the green chloroplasts and are very well adapted to their task. They are near the upper side of the leaf where they can obtain the maximum amount of light, they are packed very closely together and contain a green pigment called chlorophyll, and these absorb the sunlight and therefore help greatly to the production of photosynthesis. The cells are arranged like a fence, these help the energy entering the surface (top) of the leaf to travel a long way through the palisade cells. To obtain the most sunlight as possible, leaves have a large surface area and the more sunlight the plant receives, the better it can photosynthesise. ...read more.

Middle

* Turn on light source (lamp) at suitable distance from plant, measured by the metre rule so it gives more accuracy. * Measure light intensity by lightmeter and record observations on the face of the lightmeter. * Next apply the light to test tube, with plant inside it (upside down) which is in water. The plant must be upside down because then the bubbles can be seen quicker and easily therefore resulting in a far more reliable experiment. Also the lamp may be moved up and down constantly so the light reaches the plant but it is preferred to leave the lamp alone. This is due to the fact that if you move the lamp then you are; then, changing its distance from the plant and therefore altering the amount of light intensity the plant receives which will make the experiment unreliable. Patiently wait until bubbles can be seen, then count and record total amount of bubbles until a given time limit (1-minute) is reached. * Record observations and repeat two more times and take average to give a concordant of reliable results. * Continue until five light intensity results, which are repeated three times each, have been observed and recorded (also averaged). Record total amount for each experiment. The following safety precautions had been considered; electricity from the light source and water from the test tube. It would be very dangerous if water and electricity would coincide with one another, as this would provide some injury to a student, as water is quite a good conductor. ...read more.

Conclusion

this is an anomaly. Another anomaly was in the first experiment for '50cm' from plant, as its value was too high compared to the remaining two results. This was dealt with easily as I took the concordant value. There were anomalies because the reading of the bubbles could be incorrect due to human error. Also the amount of carbon hydroxide which was put in might not have been the exact same thus causing anomalies as this affects the process photosynthesis due to carbon dioxide being one of the main component for photosynthesis. Another factor is that the Canadian pondweed I used was not the same one I used throughout the whole experiment. This would certainly cause anomalies as different plants have different abilities to produce photosynthesis. The conclusion is reliable because I have quite accurate and reliable measurements with good scientific understanding applied to it. My method was very good and it provided some very good results. If I re-did the experiment I would use the same plant throughout the experiment, use the exact amount of carbon hydroxide and also take an average after five results, therefore a total of twenty-five experiments. An alternative way of measuring the same outcome variable is to use a manometer. This would have been much better and very accurate in measuring the rate of photosynthesis. This would overcome problems such as counting the bubbles and less chance of human error. The experiment would have provided very reliable results. Here is a diagram of what I would do. Husnain Ali Biology Coursework: How light intensity affects the rate of photosynthesis 1 ...read more.

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