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An Experiment to investigate a factor affecting the rate of Transpiration From a Shoot of Privet (Ligustrum ovale).

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An Experiment to investigate a factor affecting the rate of Transpiration From a Shoot of Privet (Ligustrum ovale) Introduction; Transpiration is the act or process of evaporation of water through the stomata (opened and closed by guard cells) underneath a plant's leaf. This water comes from the process of photosynthesis because not all the water, which is taken up by the roots by osmosis, actually makes it into the process of photosynthesis. This is because the plant could either be in the dark, or it has more water than is necessary in its leaves. Transpiration is a process that the plant does not want to take place, but it happens because of the need for Carbon Dioxide. The only way that a gas could get into a leaf is through gaps in the outer cuticle. These gaps, also known as stomata, also let the water out as transpiration. Water is near the stomata because this is the 'spongy' area of a leaf so this is where the 'wet cells' are to store the water for photosynthesis. Plants control the water loss through these stomata by being able to close them up. ...read more.


Key Factors; There are many key factors that affect the rate of transpiration including temperature and the amount of surface area on the plant. Throughout my experiment I will have to keep these factors constant to make this experiment fair. I will keep the temperature constant by measuring it and either opening or shutting the windows or using other means of raising or lowering the temperature. The wind is the factor that I will vary throughout my experiment. I will be using a fan that I can set to many different speeds and also I could move it closer and further away from the plant. Preliminary work; Before a finally set up my experiment (and apparatus shown below) and recorded the results for the graph I completed some preliminary work in which I found out some glitches to look out for. Firstly I found that it was very hard to have only water in the tube and no air bubbles, because if there are any bubbles in the tube then the area of uptake for the plant is greatly decreased and therefore less water would be taken up in a specific time. ...read more.


When the bubble moves along as far as I want it to then I will use the water reservoir to push the bubble back into its original position to repeat the experiment again. I am doing this again because then I will receive more accurate results for my graphs. For this experiment the wind speed is the independent variable so that I can measure the rate of transpiration. But it will actually measure the rate of water uptake, which is almost 99% due to transpiration. The temperature is a variable, which I will control by closing the windows and doing the experiments at the same time of day. The last variable is light, which I will keep constant by shutting the blinds and only having the light from the room lights. Lastly I will soak the plants' stem in water before each experiment because then this will prove that the water taken up by the plant is only transpiration and not for storage in the stem and the leaves. I will then place my results on a graph of water uptake against time. I am hoping that I will receive a graph like to one I drew above. Joshua Tucker 1 ...read more.

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