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Investigate factors affecting rate of transpiration in a leafy shoot.

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Introduction

Transpiration Investigation. Aim: the purpose of this investigation is to measure and investigate factors affecting rate of transpiration in a leafy shoot. Materials: * 4 - test tubes * Tin foil * 4 leafy shoot * Test tube rack * Sticky labels. * Top - pan balance Method: Select a suitable leafy plant, cut off 4 shoots from it. o Weigh the shoots and record their weights. o Fill the 4 test tubes with the same volume of water. o Mark the water level on the test tube. o Place the test tubes in a test tube rack. o Cover the openings of the test tubes with tin foil. o Push the shoots through the tin foil coverings and leave them in the test tubes. NB: be careful not to break the shoot or create too big a hole in the covering. o Using sticky labels, label the test tubes: Controlled * Warm * Dry * Windy * Place all the test tubes into the environments they've been labelled with for the same length of time. ...read more.

Middle

Both events result in a steeper concentration gradient of water molecules from leaf atmosphere to external atmosphere. The steeper this gradient, the faster is the rate of diffusion. Alternatively, it can be said that water potential increase inside the leaf while decreasing outside the leaf. In still air a layer of highly saturated air builds up around the leaf, reducing the steepness of the diffusion gradient between the atmosphere inside the leaf and the external atmosphere. Any air movement will tend to sweep away this layer. Thus windy conditions result in increased transpiration rates, the increase being most profound at low wind speeds. High winds may result in closing of the stomata, stopping transpiration. Safety: in an easy, non-complicated experiment such as this there are no major safety precautions to take to mind. Just be sensible. Results: Starting Water Level Finishing Water Level Difference Starting Mass (g) Finishing Mass (g) Loss of Water/per unit mass (ml/g) ...read more.

Conclusion

A good point being, the test tubes were covered in an attempt to reduce evaporation of the water. Evaporation would have caused wrong results to be obtained on the rate of transpiration. One factor I feel could have been improved was the shoots that were used. The shoots were very different in that they had different number of leaves, different stem lengths and thickness. I feel that all these do affect transpiration. Remembering that leaves are the surface from which water is lost therefore the more the leaves the bigger the surface area from which the water can be lost. Some shoots had more of their stem in the water than others. Another factor is the volume of water that was used. At the start of the experiment a measuring cylinder should have been used to measure the same exact amount of water for all the test tubes. I feel that potometers should have been used for this experiment instead of test tubes. Four potometer should have been set up in their different environments. They would have increased the accuracy of the results obtained and would have made the investigation more fair. ...read more.

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