The transportation of water in the xylem, which is responsible to the transportation of water, is regulated by water potential . The difference between these water potentials causes eater movement from a region with high water potential to a region with lower water potential. In addition, solute concentration, gravity and pressure can affect the water potential. Water enters the plant through osmosis. In plants, when water enters the cell, it fills the vacuole. As a result, cell will be turgid. However, when water exits the cell, the shrink king of the cell vacuole will occur.
This kind of things happens in the stomata. The stomata opens, when the cell will become turgid, however, it closes when the cell will be flaccid . Closing and opening the stomata, which mainly depends on some notations and regulated by guard cells, facilitate the water loss through transpiration. There are some factors that can affect the rate of transpiration. For example, temperature, air current and light intensity [11. Also, the rate Of transpiration varies to the plants in different conditions.
This practical aims at obtaining estimates for the rate of transpiration from a plant shoot in different conditions, such as windy and light conditions; at establishing how different factors affect the rate of transpiration and at evaluating the photometer, which will be used in this practical, as a piece of apparatus for assuring transpiration. Hypothesis: In every experiment, there will be a water loss, but especially under windy and light conditions more water will be uptakes by the plant shoot. Safety precautions During this laboratory work scissors were used to cut the plant shoot, so we should be careful while working with them.
In addition, be careful while assembling and handling the glass photometer, because it is very easy to break the long glass tube and also easy to cut yourself with the broken ends. If the sap from the plants Irritates your skin, then, tell it to the lecturer or teacher assistant. Moreover, we should wear eye protective equipment (goggles), gloves and a lab. Coat during the whole session. Also, We should keep the general laboratory precautions to avoid any emergency situation. Materials and Methods Procedure First of all, the apparatus was set up according to the provided diagram. The U-tube was placed and stood on a flat level surface.
It was ideally placed in the location where we did all our testing. Do not move the photometer since it was assembled. Water was added to create a meniscus on the top of both ends of the U-tube. A plant shoot that will fit into one hole bung was picked. The stem was cut under water before being placed in the bung. It is very important to make sure that you do not cover the leaves with water while setting up the apparatus, because this will affect the results. In addition, Baseline can be used to create a seal around the bung in order to make sure that there is a tight fit around the stem.
There must be no trapped air in the apparatus and U-tube was checked for bubbles. Then, the second bung with the graduated pipette was placed into the second stopper, making sure that the water on the left side of the U-tube was still just above the top of the be. Check for air bubbles was done, and if there is an air bubble start again and try to remove these air bubbles. The water was fairly high in the pipette so that a series of readings under different conditions could be done. All observations were clearly recorded into the logbook. Rest Its: Table 1 . Volume of water used during time intervals.
Time (min. ) Normal condition Windy condition Light condition 0. 50 ml 0. 10 ml 0. 05 ml 3 0. 70 ml 0. 20 ml 5 0. 85 ml 0. 40 ml 7 1. 00 ml 0. 15 ml Rate of transpiration 0. 14 ml/min 0. 07 ml/min 0. 02 ml/min Rate can be calculated using this formula: Rate of transpiration (normal condition) , Rate of transpiration (windy condition) = Rate of transpiration (light condition) = ; Average rate of transpiration (under all conditions) = Graph 1. Volume of water used vs.. Time (under normal condition) Graph 2. Volume of water used vs.. Time (under windy condition) Graph 3.
Volume of water used vs.. Time (under light condition) Discussion The purpose of this practical was to examine the rate Of transpiration under different conditions, such as normal, windy and light conditions. In the first experiment under normal conditions, the volume of water used increased as he time went by. The highest value, for volume of water that was used, was recorded as 1 ml at 7th minute. According to graph 1, the best fit line goes up steadily as the time passes by. This shows us that after cutting the plant shoot, it is still functioning and water is transported to the cells.
In the second experiment under windy condition, the rate of transpiration increases slightly. It seems to be incorrect in terms of ‘slightly, because as it was under windy conditions the rate of transpiration should be greater compared to normal condition. For example, at 7th minute volume under normal condition was ml, whereas volume under windy condition was 0. 5 ml. In biological terms, more water vapor is carried away from the near the leaf surface by increasing wind speed. Moreover, anemometer showed 23. Km/h. As a result, the rate of diffusion of water from the stomata also increases.
The humidity in the spongy mesosphere, particularly in the intracellular space, is reduced and the rate of evaporation from the cell is also increases. This would lead to the greater consumption of water by the plant shoot. However, we started this experiment after 7 minutes, and our plant shoot could have taken enough Water So that less water Was uptakes under windy conditions. The volume used by the plant shoot increases slightly and the values are O. Mil at 1st minute, 0. Ml at 3rd minute, and at 5th minute the volume doubles and shows 0. Ml, and finally 0. Ml at 7th minute. In the third experiment under light condition, the rate of transpiration also increases slightly. The best fit line goes up as the time went by. At 3rd and 5th minutes the volume was the same with 0. Mimi. After that, at 5th minute the volume increases moderately to O. Mil and to 0. 1 mi at 7th minute. Under light condition we should take onto account that not only light affects the rate of transpiration, but also the temperature, since over time the bulb heats up and consequently, temperature will also increase.
Moreover, experimental data do not correspond with my hypothesis, because the results partially contradict the theoretical facts, but it does not mean that my hypothesis is 100% wrong. And here the question arises about apparatus that was used, namely photometer. From this point, we can already assert that this kind of photometer is not an appropriate device to measure the rate of transpiration, since our results are to valid. Another noticeable feature is that there might be some errors during these experiments.
One of them is that our results may not be accurate, since the main problem was to put plant shoot, making sure that there were no air bubbles inside the U-tube. These air bubbles could affect the final results, since water will not be uptakes by the plant shoot. Also, we should be careful while working with the baseline, since if some baseline will be on the stem of our plant shoot, the plant shoot will not be able to take any water and our experiment could end before it started. Another error might occur while reading the value from the graduate pipette.
And also, the rubber connection between two parts of U-tube was the most uncomfortable part in terms of water filling. While adding water to the U-tube in middle of that rubber connection there always was some air bubbles. But, we were lucky and we have overcome this problem by using several attempts to get rid of air bubbles. Finally, we got U-tube without any bubbles. However, the rubber connection could greatly influence the final results, since this rubber connection between two parts of U-tube was highly sensitive, which caused omen problems with reading the scale on the graduated pipette.
In addition, there is another factor that affects the rate of transpiration which is surface area. As the surface area increases, the rate of transpiration goes faster. Furthermore, there is a suggestion that can improve this practical. Think that we should set up a chamber with consistent and controllable air current with the temperature that can vary. It is important to find an appropriate apparatus in order to make our results more valid and accurate. With this particular apparatus that we used in our practical we will never get valid results.
Conclusion TO sum up, three experiments were done under different conditions, namely under normal, windy and light conditions. In all three conditions the rate of transpiration increases as the time went by. However, the results under windy and light conditions were unexpected, since according to some books I thought that under windy and light conditions there will be more water uptakes, but the results partially contradict my hypothesis. In addition, we did this practical only once so that our results are unreliable. Since our results are unreliable and not valid, I dare to believe that my hypothesis is correct.
Moreover, some errors that could be during this practical were identified. For example, wrong reading the scale on the graduated pipette or the presence of air bubbles. Furthermore, to improve this practical and to make our results more valid, we should set up a chamber with consistent and controllable air current with the temperature that can vary.