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What factors affect the rate of transpiration.

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Date of investigation: 22nd May 2001 Title: Transpiration Question: What factors affect the rate of transpiration. Factors: Various environmental factors affect the rate of transpiration in a plant. Here are a few: - Temperature A temperature increase means that the water will evaporate more rapidly from the leaves of a plant causing more water to be absorbed through the roots. The thermal energy also helps to make the chemical reaction between carbon dioxide and water happen more often to make glucose more efficiently. As photosynthesis only use's 1%-2% of the water taken out by the roots this causes little change on the rate of transpiration. Availability of water The plant will have trouble transpiring steadily if the amount of water loss is more then the uptake of water by the plant. If the rate of transpiration exceeds the absorption of water, loss of turgor occurs. (The explanation of turgid can be found in my background information.) As a result of this the stomata closes, which leads to an immediate reduction in the rate of transpiration and photosynthesis. The loss of turgor in the plant causes it to wilt. Light intensity The sunlight warms up the plant causing more evaporation to occur on the surface of the leaves. The presence of light also stimulates the opening of stomata. The size of stomata this has a great impact on the rate of transpiration. The larger the stomata the more water vapour diffused from the stomata. This is the reason plants transpire more rapidly during the day. Wind factor When the air starts to fill with water vapour the humidity starts to affect the plant. ...read more.


By being able to view three sets of results I shall be able to circle out any anomalous results. My geranium will only be able to stay healthy for a few days. I will try to do the experiment efficiently to gather accurate results. While doing the experiment I will need to take a few precautions. When I am placing the geranium shoot into the rubber tubing I will try not to bruise the xylem cells, as this will affect the plants uptake of water. If that happens I cannot keep the uptake of water consistent. What to measure It is not easy to measure the rate of transpiration but I can use a potometer to measure the rate of water uptake. I know that the amount of water loss is less then the water taken up by the roots as some of the water is used for photosynthesis. I will move the fan 20cm at a time until the fan is 80cm away. I chose these measurements because earlier in my preliminary work I moved the fan 10cm at a time. I found out that this distance was too short because there was not much difference displayed between 10cm and 20cm, 20cm and 30cm and so on. Now I am moving the fan 20cm at a time, as this will show much clearer results. The air bubble in the capillary tube will be measured for 3 minutes for each fan distance. At first I decided upon 30 seconds but this did not show clear differences in the results. ...read more.


To obtain more accurate results I need to have repeated the experiment several more times to approach nearer to the accurate results. Reliability of method. My method was unreliable because it took to much time to carry out. The weather and the health of my geranium plant affected my results. The weather was never consistent; it may be hot one day and cold the next. If the xylem tubes of the plant were not in working order it would affect the rate of water uptake. I should have included a reservoir near the end of the capillary tube. When the experiment is finished I wouldn't have needed to wait for the air bubble to travel all the way to the stem of the plant. With the reservoir I can use a syringe to push water out of the capillary tube. The water will push the air bubble out of the capillary tube in a matter of seconds. To obtain an accurate result on the topic I should have looked at a wider range of plants and environments. I could look at different species of plants for example a cactus. A cactus takes up a lot of water trough it's roots but has a small percentage of water loss. The cactuses leaves have a small surface area because they cannot afford to loss much water as it hardly rains in the desert. I could also look at plants that live in water. These are some questions I could ask. The water vapour outside the plant cell is greater so how do they transpire? Does heat and light have much affects on the plants that live deep on the seabed? Could it be that they do not transpire or photosynthesis? 1 Mahbuba Begum 9DW ...read more.

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