Transpiration Lab Report-2 4oa17

Camila Vela 3 Period AP Biology April 30, 2014

Measuring the effects of environmental factors on the rate of transpiration 1. Objective: Understand which environmental factor will cause the highest amount of transpiration. 2. Research Transpiration is the evaporation of water from the roots of the plant to its leaves. It is the process in which moisture is carried through plants beginning at the roots and ending on the end of the stomata outside of the leaves. In here something that plays a very important role is the water potential (tendency of water to move across a membrane from one area to another) because water molecules move from a higher water potential to lower water potential (Pearson, 2013). In this process water is transformed into vapor and is released into the atmosphere. Transpiration also includes a process called guttation “which is the loss of water in liquid form from the uninjured leaf or stem of the plant principally through water stomata” (Perlman, 2014). Being that said, the stomata are tiny pores that are controlled by guard cells is the main exit for transpiration in plants. When the stomata are open the rate of transpiration increases, whereas when they are closed the rate of transpiration decreases. The guard cells control what comes in and out of the stomata, therefore it restricts the pores’ opening. A guard cell can be turgid when there is large amount of water, which allows the stomata to have a wider opening (Pearson, 2013). Transpiration when exposed into different environmental factors such as: Humidity, mist, and temperature the process have different reactions. When we talk about light (temperature), we see that the effect it has on the process is the increment of the rate of transpiration, because plants transpire more in light than in darker places. At the same time this occurs because light stimulates the stomata to open, allowing water to come out. In that way, one of the roles light has is that it warms the leaf, making water come out faster (NA, 2011). All this is possible because the opening of the stomata allows more carbon dioxide into the plant (for photosynthesis) that generates the increase in transpiration (BBC, 2014). Another environmental factor is humidity. Research demonstrates that a plant when exposed to humidity decreases the rate of transpiration because the diffusion of water vapor is delayed if the leaf is surrounded by moist air. That is why transpiration is more effective in dryer air than a thick air because it is more condensed with water molecules. This also means that the difference between the water potential in the plant and on the environment is less, therefore there are less molecules being transpired (Burba, 2013). Finally, wind is another environmental factor regarding the transpiration process. As previously stated when a plant is exposed into a moist environment the rate of transpiration decreases, in contrast when it is exposed for example to wind the rate of transpiration 2

increases. It increases because wind removes the extra water molecules that are located in the environment, this speed up the diffusion of water vapor coming out of the leaf. Never the less, plants like the jade, orchid, or cactus that grow in very dry environments; have developed another method for transpiration without the loss of water. This method is known as CAM (Crassulacean Acid Metabolism). These plants utilize a specific carbon fixation pathway in where the stomata only open at night and closes during daylight to avoid any water loss because the environment is too hot.

3. Hypothesis: Null: Environmental factors will have no effects on the rate of transpiration of Impatiens plant Alternative: Environmental factors like temperature will have effect on impatiens Experimental: If Impatiens is exposed to environmental factors such as an increase in temperature, then it will have a higher rate of transpiration, because the temperature source also emits light this will cause the plant to open its stomata so more carbon dioxide comes into the plant for the process of photosynthesis. 4. Experimental Design: Manipulated Variable

Responding Variable

Constants

Control

1. Environmental Factors:

1. Rate of Transpiration (measured in ml/m2/min )

1. Type of plant (Impatiens)

1. Potometer without environmental factors

˚ Humidity( Mist)

2. Surface area of the leaf (m2)

˚ Wind (Fan)

3. Room Temperature (22˚C)

˚ Temperature (Light bulb)

4. Amount of water in tubing (ml) 5. Temperature of water (22˚C) 6. Distance between environmental factor and potometer (30 cm)

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Manipulated Variable

Responding Variable

Constants

Control

7. Time intervals (every half hour) 8. Pressure in the environment (PA) 9. Exposure to the room light (sunlight/lamplight) 10. Same diagonal cut on the plant (45º) # Of Trials: 1 5. Materials: 1. Plant (Impatiens) 2. Plastic tray (one) 3. Plastic tube (one) 4. Ring stand 5. Knife (one) 6. Test tube clamps 7. 2 pipettes (1 milliliter) 8. Ruler 30 cm (one) 9. Marker (one) 10. Syringes 3 ml (one) 11. Transparent Tape (one) 12. Stopwatch (one) 13. Petroleum Jelly 14. Fan (one) 15. Light bulb (one) 16. Plastic bag (for mist) 17. Water (enough as needed) 18. Lab coat 19. Stop watch 20. Hose (check for leaks) Procedures: 1. Using the potometer along with the millimeter construct the pipette and the plastic tubing. a) Attach the millimeter pipette to one end of the plastic tubing. 2

b) Fill the construction with water by using the plastic syringe (Make sure there a

2. 3. 4. 5. 6.

) re no air bubbles present inside the tubing)Fix the construction on the ring stand (do not allow any water spill). With the scalpel cut a small section of the plant. Place the cut plant on the tip of photometer’s tubing. Seal the opening between the plant and the tubing with petroleum jelly (place the jelly around the plant and the tube) Let the experiment rest for ten minutes. Record the water level on the millimeter pipette section of the potometer at time zero. (This means after the 10 minutes have ed). a) Record the water level at a three minute interval for thirty minutes.

7. After thirty minutes have ed, remove the plant from the potometer and cut all of the plants leaves. 8. Calculate the leaves’ surface area with the paper your teacher gives you. 6. Results Table 1: Measurements of the water decrease (in ml) in the potometer time in minutes Treatment

0

3

6

9

12

15

18

21

24

27

control

0,00 0

0,002

0,003

0,003

0,004

0,004

0,004

0,005

0,005

0,005

light

0,00 0

0,004

0,006

0,009

0,014

0,017

0,024

0,033

0,037

0,046

light (w/obs)

0,00 0

0,005

0,006

0,007

0,008

0,009

0,011

0,012

0,015

0,019

fan

0,00 0

0,003

0,010

0,015

0,021

0,029

0,034

0,040

0,048

0,052

mist

0,00 0

0,008

0,008

0,009

0,009

0,009

0,010

0,010

0,010

0,011

Table 2: Calculated surface area of the plant used: treatment control

surface area m2 0,003500 2

light no obs

0,009500

light

0,004600

fan

0,007500

mist

0,007100

Table 3: Calculated rate of transpiration (ml/m2) ml/m2 time in minutes Treatment

0

3

6

9

12

15

18

21

24

27

control

0,0 0

0,57

0,71

0,86

1,14

1,14

1,14

1,43

1,43

1,43

light

0,0 0

0,42

0,63

0,95

1,47

1,79

2,53

3,47

3,89

4,84

Light (w/obs)

0,0 0

1,09

1,30

1,52

1,74

1,96

2,39

2,61

3,26

4,13

fan

0,0 0

0,40

1,33

2,00

2,80

3,87

4,53

5,33

6,40

6,93

mist

0,0 0

1,13

1,13

1,27

1,27

1,27

1,41

1,41

1,41

1,55

Analysis

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Rate of transpiration in ml/m2/min 8.00

Water level (ml)

7.00 6.00 5.00

Control Light Light (with obstac Fan Mist

4.00 3.00 2.00 1.00 0.00 0

8

15

23

30

38

Time (minutes)

Looking at the table and the graph we can see that there is an obvious effect by the different environmental factors being used during the experiment. As we can see the environmental factor with the higher rate of transpiration was wind, starting at 0.4 ml/m2 in minute 3 and then at minute 15 3.8 ml/m2, finally at minute 30 7.8 ml/m2. This demonstrates that wind created the highest amount of transpiration during the 30 minutes. Followed by the environmental factor of light without an obstacle which in minute 3 obtained 0.4 ml/m2 , in minute 15 1.7 ml/m2, and in minute 30 5.7ml/m2 . The control group along with the mist group had similar results (as the table demonstrates). Finally, the mist group was the one to have the lower results for transpiration. Being that at minute 3 it obtained 1.1 ml/m2, minute 15 1.2 ml/m2, and minute 30 1.5 ml/m2. As we can see the results had no greater increase than 1.5, meaning that it remain (in a way) constant during the whole experiment. Another thing that we should take into is that the control group and mist group had very similar results starting around minute 12 all the way to minute 30. Giving us the idea that not having an environmental factor at all or having mist will result in a lower rate of transpiration. 7. Conclusions:

The purpose of our experiment was to find out the effect different environmental factors like wind (fan), temperature (light), and humidity (mist) have on the rate of transpiration. At the same time we had to find out which environmental factor had the greatest increase of transpiration for the plant impatiens. The major findings we gathered surprised me a little bit. Given for the fact that I thought at first that increasing the temperature would diminish the rate of transpiration because the stomata of the plant would close, inhibiting the loss of water. In reality when you increase temperature as the research demonstrates, it stimulates the stomata to open 2

allowing the water to come out. This means that the guard cells are constantly open for water to get out. At the same time this allows diffusion of Carbon dioxide in, which is needed for the process of photosynthesis. Wind (fan) was the group that generated the highest rates of transpiration. Wind removes the extra water molecules that are located in the environment, speeding up the diffusion of water vapor coming out of the leaf. Furthermore, before we started the experiment our teacher Jen told us that if we did not have a control group we could use the light with obstacle as the control group. Never the less, as the graph and table demonstrates that mist was the most similar (in results) to our control group. This was due to the fact that a plant when exposed to humidity decreases the rate of transpiration because the diffusion of water vapor is decreased if the leaf is surrounded by moist air. That is why transpiration is more effective in dryer air than a thick air because it is more condensed with water molecules. This also means that the difference between the water potential in the plant and on the environment is less, therefore there are less molecules being transpired because. My hypothesis stating that If Impatiens is exposed to environmental factors such as an increase in temperature, then it will have a higher rate of transpiration, because the temperature source also emits light this will cause the plant to open its stomata so more carbon dioxide comes into the plant for the process of photosynthesis, was ed by my findings because the research and the results demonstrate that despite being the second result with the highest rate of transpiration, it increased the rate of transpiration more than mist or light with an obstacle. This was due to the opening of the stomata influenced by the presence of light. Some possible explanations that may be seen in the experiment is that despite wind (in the form of fan) was the group to demonstrate the highest rate of transpiration; temperature was the second group to demonstrate the highest rate of transpiration. This was due to the fact that it was benefited from the opening of the stomata to diffuse more carbon dioxide in, by that it left open the stomata and more water was released. Meaning that it was not the first cause (temperature increased transpiration) but directly related to photosynthesis which was in reality the first cause for the opening of the stomata. All this was given by the presence of light that influenced the opening of the guard cells of the stomata. The findings of our experiment were very similar for the ones found in other research such as in biology junction where it demonstrates that the major increment of transpiration was not given by wind (fan) rather by light (which was 4 ml/m2 ). Meaning that light has a positive impact in transpiration. Some human errors that were introduced into the experiment were for example that my group (control) experienced a leak from the hose, so we had to repeat the experiment one more time to secure the results. Another error was that at times you could get confused in the way we had to measure because we had to add another pipette and at first I thought we were measuring the rate of transpiration, but we were actually measuring the decrease of water after the ten minutes interval. Some recommendations I could offer would be the fact that school does not give enough time for experiments that are fundamental for an AP level course as this class, AP Biology, I think that students should have enough time so they do not rush with the results. Also a change I would do to the experiment would be instead of only 2

doing one group of the environmental factors (because of time) I would encourage students to experiment with all of the experimental factors. Finally, some recommendations for further study would be to experiment with different variables. For example you could change instead of testing high temperature you could decrease the temperature to check if it decreases, increases, or remains neutral the transpiration rate. Also, you could change the plant and experiment each manipulated variable in different types of plants. For example, cacti we know they are C4 plants, what would happen if we place them in a very cold environment? Or develop the experiment during night? It is quite interesting to see the evolutionary history plants hold because of their various adaptations they have had into the different environments in the world, and becoming more evolutionary organisms.

Works Cited BBC. (2014). Transport in plants. Retrieved May 18, 2014, from http://www.bbc.co.uk/schools/gcsebitesize/science/add_gateway_pre_2011/greenworld/pl anttransportrev2.shtml Burba, G. (2013). Transpiration. Retrieved May 20, 2014, from http://www.eoearth.org/view/article/156689/ Campbell, N. and Reece, B. (2005). AP Edition Biology, Seventh Edition. Pearson Education: San Francisco. N, a. (n.d.). CAM plants. Retrieved May 20, 2014, from http://www.biologyonline.org/dictionary/CAM_plant N, a. (2014). Transpiration - Water Movement through Plants. Retrieved May 17, 2014, from http://el.unl.edu/pages/informationmodule.php?idinformationmodule=1092853841&to picorder=6 N, a. (2011). Transpiration. Retrieved May 18, 2014, from http://s.rcn.com/jkimball.ma.ultranet/BiologyPages/T/Transpiration.html

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