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Factors affecting the rate of transpiration

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Factors affecting the rate of transpiration page * Introduction 2 * Pilot Experiment & Risk 5 * Method 6 * Results 8 Results under standard conditions 8 Results at wind speed 1 8 Results at wind speed 2 9 Results at wind speed 3 9 * Analysing Results 10 Analysing evidence and drawing conclusions 10 Evaluation evidence and procedures 12 Experimental limitations 12 Extending the investigation 13 * Appendix 14 Index of Appendix: 14 Graph A 15 Graph B 16 Extended Results: Temperature and wind effect on plant 17 Graph C 18 Calculations: For graph A 19 For graph B 20 Hypothesis: My hypothesis is that if the intensity of the wind is increased then the rate of transpiration of a plant will increase given that humidity, light, pressure and temperature stay the same. Introduction: Water normally leaves the plant as water vapour. The change from a liquid state to a vapour state requires the addition of energy which is provided by the sun, and it is this energy that maintains the flow of water through the entire plant. Transpiration can occur through the stomata, cuticle or lenticels. Water is brought to the leaf in the xylem vessels. The xylem is part of the vascular bundles which spread to form a fine branching network throughout the leaf. The branches end in one or a few xylem vessels that possess little lignification. Water can therefore escape easily through their cellulose walls to the mesophyll cells of the leaf. There are 3 main theories of how the water moves from the roots to the leaf. The apoplast pathway, symplast pathway and vacuolar pathway. The apoplast is the system of adjacent cell walls which is continuous throughout the plant. Up to 50% of a cellulose cell wall may be "free space" which can be occupied by water. The symplast is the system of interconnected protoplasts in the plant. ...read more.


mm/20s 1 2 3 4 5 6 7 8 9 10 Average ?ave For the calculation part of this experiment I measure the diameter of the capillary tube which is 0.0013m or 1.3mm. Therefore the radius is 0.00065. The formula for the rate of transpiration is ?r��(distance travelled(?ave)) / leaf area / time. The ?ave in this experiment is the sum of the averages I obtained from the 3 experiments. The leaf area is .221m� and the time was 200s. To complete the table repetitions of the same experiment have to be taken. Therefore I repeat every experiment at least 3 times. The room temperature (23�C), pressure, humidity, light are kept constant to an extend. This is due to that pressure cannot be influenced as well as humidity. Temperature can be affected by heaters in the room and light by turning them on or off. Results I measured a time interval of 20s and achieved the following results: Measurement under normal conditions Measurment 1st check 2nd check 3rd check Average In mm/20s 1 6 7 6 6.33 2 6 7 7 6.67 3 6 6 7 6.33 4 7 7 7 7.00 5 6 6 7 6.33 6 6 7 7 6.67 7 7 7 7 7.00 8 4 6 7 5.66 9 6 7 6 6.33 10 6 6 7 6.33 Average 6.0 6.6 6.8 ?ave64.65 Calculation of the rate of transpiration: ?r��distance travelled(?ave) / leaf area / time ? � (0.00065m)� � 0.06465m / .221m� / 200s = 1.941 � 10-9 dl m-� s-1 1.941 � 10-9 dl m-� s-1 � 60s = 1.164 � 10-7 dl m-� min-1 Measurement at air current using fan stage 1 Measurement 1st check 2nd check 3rd check Average In mm/20s 1 8 7 9 8.00 2 7 8 8 7.67 3 9 9 7 8.33 4 8 9 7 8.00 5 8 8 8 8.00 6 7 7 9 7.67 7 8 8 8 8.00 8 8 8 8 8.00 9 7 7 8 7.33 10 8 8 7 7.67 Average 7.8 7.9 7.9 ?ave78,67 Calculation of the rate of transpiration: ?r��distance travelled(?ave) ...read more.


the stomatal pores started to close after being affected by the wind. Therefore the starting point is higher than at stage 1 (lowest wind speed) but the speed at which water is taken up is steady and similar to the stage 1 (lowest wind speed) speed. Also the stage 3 (highest wind speed) results are very similar to the stage 2 (intermediate wind speed) results. It shows that from stage 2 (intermediate wind speed) the stomata are affected and reacting on the fact that wind is blowing on the leaves. Anomalies in the results section were achieved because the bubble in the potometer sometimes made a jump or got stuck for a second. Those results were mostly eliminated due to repeating the experiment. Experimental limitations There was only limited time to improve the experiment changing different key variables, or increasing the number of repetitions. Further investigation on the effect of temperature as well as the effect of humidity would lead to an interesting investigation. More repetitions could be made having more time. Therefore the results would be more exact. The control of the wind speed in this experiment could only be achieved using a simple fan. Therefore only arbitrary units can be given when drawing the graph. An exact wind speed may lead to better results and graphs. Improvements could be made by using a fan where a determination of the exact wind speed can be made. The graph produced from this would give a much better result. When introducing a bubble into the system the bubble should be always the same size because the bubble might flow up slower when it is bigger due to the force acting between the bubble and the capillary tube. Extending the investigation Further investigation on the effect of temperature, different speeds of wind, different distances as well as different positions of the wind origin would improve this experiment. Using different plants as well as changing different key variables humidity for instance also would improve this experiment. ...read more.

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