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Find out what factors affect the rate of photosynthesis. Rate being the amount of photosynthesis produced per minute.

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Aim: To find out what factors affect the rate of photosynthesis. Rate being the amount of photosynthesis produced per minute. Variables: Equation for Photosynthesis: Representing sunlight Co2 + H2O Glucose, ATP and O2 - Temperature. Because Photosynthesis is an enzyme based reaction and enzymes dependant on the temperature. As we know, enzymes work better when the temperature increases, and they can be frozen if the temperatures are too low. However, when the temperature is too high, the enzymes could denature and therefore the plant would die and no photosynthesis would occur at all. - Light intensity, Because sunlight is needed for photosynthesis to occur. Sunlight is needed for the plant to turn into food. This process is Photosynthesis, so without Sunlight, there is no photosynthesis. So then this basically means if u give the plant more sunlight (higher light intensity), there is more photosynthesis to make more food. - Concentration of Co2 in water. Because Co2 is needed for Photosynthesis to occur. So then if there were a higher supply of Co2, there would be more photosynthesis. Therefore the concentration of Co2 in the water is able to affect the rate of photosynthesis. - Amount of water. Because water is needed for photosynthesis to occur. Without water, a plant cannot photosynthesize; meaning that Photosynthesis is also dependent on the amount of water. So then if we change the amount of water, so will the rate of photosynthesis. - Colour of light. Different frequencies of light can affect the rate of photosynthesis. Since the colour of chlorophyll is green, it means that the plant will reflect green colour light and absorb the other colours of light accordingly. - Different type of plant. Because the leaf structure, and amount of chlorophyll is different in each plant. For example, if a plant has more leaves (chlorophyll), it is likely to photosynthesize more than a plant that has less leaves (less chlorophyll) ...read more.


per 5 minutes. If I were to do this experiment again, I would therefore use a cm cubed gas measurer than a cm one. Another point is that too much Sodium hydrogen bicarbonate was used. It was maybe too strong and therefore harmed the plant making the result for 20 cm no photosynthesis at all. Therefore, a better way to do this experiment is to use more water in the sodium bicarbonate solution. I also recorded the results from furthest distance to the closest distance e.g.: from 20cm to 15cm, to 10cm. This makes my results inaccurate because the plant needs time to adapt from a lower light intensity to a higher light intensity. For example, the reading for 0 cm should be higher than it is, because I included the adaptation time in the 10 mins allowed for the plant to photosynthesize. Therefore if I were to do this experiment again, I would take readings from closest distance to furthest distance or either give the plant a slight adaptation time. Actual Experiment Apparatus - Gas measurer - Beaker - Sodium hydrogen bicarbonate (100ml) - Funnel - Ruler - Lamp - Sheet of glass - Water (150ml) - Pondweed (16cm) - Clamp - LUX meter (to measure light intensity) Fair test: In order for the experiment to be a fair test, all the other variables apart from the chosen variable must be controlled. In this case, the chosen variable is light intensity. - Temperature. In order to keep the temperature constant, I will use a sheet of glass to screen off most of the I.R energy emitted by the lamp. By doing this, then the light intensity is hardly affected (because the glass is transparent) but then the sheet of glass absorbs much of the heat. - Light intensity. In order to keep the light intensity consistent, the same power light bulb will be used each time. ...read more.


In result I should have started measuring further away from the plant so that I could use light intensity instead. Also, the experiment is about light intensity vs. rate of photosynthesis, so it would be more relevant and clear to directly use light intensity rather than distance. Further more, I think the lamp in the experiment was not strong enough to allow the limiting factors to take place. Therefore I cannot identify them from my results. Therefore if I had to repeat the experiment, I would use a stronger light bulb. The bulb itself is about 3 inches away from the lamp-head, this means that when my results was recording 0cm, it actually meant 3 inches. This issue is very hard to improve, provided that we can take off the head of the lamp. Also, it was hard keeping the classroom pitch black so that the plant is only photosynthesizing the light emitted from the lamp itself. Also, everyone in the classroom is working close to each other, in result the plant I was working with may have photosynthesized the extra light emitted from other lamps around the room. So if I had to do the experiment again, I would do it by myself in a pitch-black room, to ensure that no extra light is affecting the rate of photosynthesis. Since the repeat experiments were conducted on different days (with different climates) then the variables have automatically changed. E.g. it was a hot day, then the classroom temperature would rise and enzymes in the plant would work at a different rate. If it was a sunny day, there would be more light seeping through the windows and this would also affect the rate photosynthesis. If I were to further investigate into this investigation, I would investigate the carbon dioxide concentration factor. Since Co2 is another element that plant needs in order for photosynthesis to occur. This is much easier to measure compared to light, and can produce just as accurate results. ...read more.

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