humidity’s effect on transpiration

7/28/2019 Humiditys Effect on Transpiration

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Burhan Riaz Spruce Creek High School

IB Biology HL/Period 3 Planning Date: 09/29/08

Richard Snodgrass Execution Date: 09/30/08

Humiditys Effect on Transpiration

Introduction:

The accurate description of transpiration is the loss of water from plant leaves.

Environmental factors play a major role in the rate of transpiration in every day plants

(Perlman). As water exits the leaf through acute spaces in the leaf called the stomata, the

rate of transpiration changes according to solar radiation, temperature, wind, and misting

(Perlman). Transpiration in plants is similar to transpiration in animals since both are

used for related purposes. One major purpose for this process is to cool the organism to a

certain level in order to maintain the best possible conditions for optimum metabolic

activity (Ritter).

Low humidity, for example, creates a gradient between the organism and the air, which

initiates transpiration (Janes). Soil can affect transpiration depending on the size of pores

between soil particles, which can cause low soil capillary, which makes it hard for the

plant to attain moisture (Ritter). In particular, this experiment addresses three of the many

transpiration-changing factors; Light intensity, relative humidity, and wind movement.

Light Intensity The intensity of light is a controlling factor of the opening and

closing of the stomata. Generally, low intensity is less effective than high

intensity. Thus, the stomata often is not open as wide on a cloudy day as on clear

days, and often do not remain open for as much of the daylight period (Perlman).

Relative Humidity As the humidity relative to the plant increases around the

organism, the rate of transpiration should fall since the plant has less reason to


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transpire in that kind of situation. It is much easier for water to vaporize into dry

air as apposed to saturated air (Perlman).

Wind movement: Movement of air has shown to increase the transpiration rate

since the moisture has less time to cool the plant due to the wind removing the

water molecules before they have a chance to have an effect (Perlman).

It should also be noted that although these factors will be measured, factors such as soil-

moisture availability and type of plant would limit the experimentation and unfortunately

vary the collected data (Janes). Since those factors are not controlled in this experiment, it

may be difficult to deduce an accurate conclusion regarding the experiment. In this case,

the effect of humidity or misting on transpiration will be measured in order to prove

higher humidity causes a lower rate of transpiration.

Problem:

Will the variation of humidity affect the rate of transpiration?

Hypothesis:

If the level of humidity is measured and altered, then there will be an effect on the rate of

transpiration on the plant. The effect should be the higher the humidity, the lower the

transpiration rate since generally speaking, as the relative humidity of the air surrounding

the plant rises, the transpiration rate falls. This makes it easier for water to evaporate into

dryer air rather than into more saturated air. Based upon this generalization, the

experiment should support the mentioned assumption although it must also be noted that

uncontrolled factors may alter the final data and thus hamper the conclusion.


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Independent Variable: Humidity (misting)

Dependent Variable: Transpiration

Controlled Variables:

Materials: Using the same materials per trial is essential in this experiment

in order to have a consistent means of measuring data. This however does

not guarantee that all instruments will record data correctly since the data

collected will be accumulated by different people at different times.

Plant type: The species used in the experiment will have to be the same

since different plants have varied reactions to factors of transpiration. (ex.

Stomata may take more or less time to open than other plants)

Testing Site: Testing will not be done in any other location besides original

place of experimentation to reduce transpiration-related factors to affect the

results. (ex. Lighting, humidity)

Light Since light is a transpiration factor, light must stay consistent

throughout the experiment to avoid trials from being different from each

other.

Humidity- This humidity is different from the humidity that is used as an

independent variable, which will be done through misting. This humidity is

already there, as an environmental factor, and it can stay constant if the

experiment is done at a single location.

Materials:

Arboricola This plant will be the standard organism to be measured.


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Utility Clamps Secures the plant in place as well as the gas pressure sensor.

Vernier Gas Pressure Sensor Determines the change in pressure when

experiment is set up. Communicates with computer.

Vernier Logger Pro 3 Program used to record and analyze data from the gas

pressure sensor.

Computer Displays the Vernier Logger Pro 3 program. Communicates with gas

pressure sensor.

Ring Stand Provides upright support for the attached parts of the experiment

(ex. Plant, gas pressure sensor)

Plastic Tubing Clamps Provides a link between the plant and the gas pressure

sensor.

Metric Ruler Measures the surface area of the leaf.

100 Watt Light Source Provides light to the plant, alters transpiration rate.

Scalpel Cuts the leaves off the plant.

Syringe Transfers water to the plastic tube.

Plant Mister Alters transpiration due to change in humidity.

This experiment involves no safety hazards and does not safety equipment.

Procedure for Controlled Variables:

1. Materials, especially measuring instruments, should not be changed at any

time during the experiment, as this will obstruct accurate data collection.

When conducting the experiment, the materials used should be noticed by

the scientists.


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2. The Arbricola plant is to be used consistently since if any other plant was

used, it may not correspond to the factors of transpiration these same way

as the Arbricola plant.

3. Testing site cannot be changed amidst the trials as this would change the

environmental factors that are already affecting the plants transpiration

rate.

4. The intensity of light is a transpiration related-factor and cannot be

changed. Using the same testing site will insure this.

5. The environmental humidity level is also a transpiration related-factor and

cannot be changed. The same testing site should be used.

Procedure for Data Collection:

1. Attach two utility clamps on an upright ring stand. One should be higher than

the other.

2. Attach the gas pressure sensor to the top utility clamp (Gravity of water).

3. Cut a piece of the plant where the leaf branches off and attach to bottom

clamp.

4. Attach a plastic tube to the end of the branching part of the leaf. Vaseline may

be used to secure in place.

5. Fill water with a syringe through the opposite side of the tube and attach to the

gas pressure sensor. Avoid any air bubbles.

6. Connect the gas pressure sensor to a computer running Logger Pro 3.


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7. To record data, click on Collect on the programs interface and click stop

after 300 seconds.

8. To visually see the rate of transpiration, left click the interface and select

Linear Fit.

9. To measure humidity, water is to be sprayed onto the plant with a mister. A

constant amount of sprays should be used. Record data through Logger Pro 3.

10. Conduct multiple trials while minding the controlled variables.

Raw Data:

Controlled Group Statistics

Surface Area (cm2) Temperature Relative Humidity Light Y2 Y1 X2 X1 Slope

62 25.4 51.2 52.1 101.08 101.3 654 0 -8.5E-0

95 25.5 55.9 546 100.002 100.57 300 0 -0.0017

91 78.3 499 494.5 101.916 102.493 903 0 -0.0012

70.5 23.8 52 400 102.95 102.78 100 300 -0.0005

119.5 24.3 54.8 49.6 101.365 101.877 328 0 -0.001

62.5 23.5 44.5 537 103.055 104 139 0 -0.0058

104 77.1 72.6 293.1 98.075 98.639 217.8 2.45 -0.000

65 77 65 46.2 100.79 101.02 361.5 0 -0.000104.9 23.9 59.5 426 99.6 100.45 421 6 0.0020

73 25.2 56.5 113 96.88 96.94 400 0 -0.000

Humidified Group Statistics

Surface Area (cm2) Temperature Relative Humidity Light Y2 Y1 X2 X1 Slope

49 69.4 78.5 79.8 105.295 105.384 264.4 0 -7.113E-0

65 77.4 81.3 47.6 100.858 101.189 299.2 0.6 -0.00057

61 25.8 82.5 251.3 102.84 103.06 400 0 1.91E-0

71 75.7 84.6 67.4 100.51 100.85 362.6 18.7 -0.00034

56.5 75 91.7 310 101.25 101.4 251.7 0 0.0005957 24.33 78.5 97.8 101.538 101.6 306 0 -0.00034

53 25.4 78.1 25 100.238 100.173 70.6 1.7 -0.00027

67.5 24.8 85.3 400 102.72 102.84 299 26 -0.0001

96 78.5 87.1 410.6 102.69 102.75 291 0 -0.0002

36.5 25.4 56.5 100.2 100.45 300 0 -0.002


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Transformed Data:

Slope (Kilo Pascals) Divided by Surface Area (cm2)

Control Humidity

-1.374 E -6 -1.45163E-06

-1.875 E -5 -8.76923E-06

-1.362 E -5 3.13115E-07

-7.506 E -6 -4.78873E-06

-9.423 E -6 1.05133E-05

-9.36 E -5 -5.96491E-06

-1.146 E -5 -5.09434E-06

-2.568 E -6 -1.48148E-061.914 E -5 -2.08333E-06

-2.548 E -6 -5.47945E-06

-1.248 E -5 N/A

-5.739 E -6 N/A

-2.911 E -6 N/A

Transformed Statistics

(Kilo pascals/ cm2) Control Humidity

Mean -1.253 E -5 -2.43E-06

Median -7.507 E -6 -3.44E-06

Standard Deviation 2.60 E -5 5.29E-06

Sample Variance 6.761 E -10 2.79E-11

Range 1.127 E -4 1.65E-05Minimum -9.36 E -5 -5.96491E-06

Maximum 1.914 E -5 1.05133E-05

Sum -1.628 E -4 -2.42867E-05

Discussion:


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My hypotheses can be proven correct by the raw and transformed data. If the raw

data is looked upon in a simple manner, it is easy to realize that individual transpiration

rates are smaller than the individual control group transpirations. This is what was to be

expected in the first place since positive humidity has a negative correlation with the rate

of transpiration. In the transformed data, the mean rate of transpiration, -3.44E-06, is less

than the mean of the controlled rate of transpiration, 1.253 E 5. Again this reconfirms

that there is a difference and it seems that when increased humidity is applied, the rate of

transpiration is decreased.

Not all of the data can be correct since the sample variation for the controlled

group is 6.761E-10 while the humidified group has a variation of 2.79E-11. Although

there are discrepancies in the total raw data, all of the transformed data recorded is in

favor of the original hypothesis and confirms the generalization about the negative effect

of humidity of transpiration. Unfortunately, what could not be measured were the P-

Values and the T-Values. These values would greatly help support hypothetical claim,

particularly if the P-Value were below .05. This brings the question whether our

transformed data is enough to have a concrete conclusion about this problem. If this

experiment could be redone, the P-value would have a lot of priority. This brings the

question whether our transformed data

Evaluation:


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Errors:

This experiment was a major resource for errors and there is a lot of reason for it.

First, many individuals were assigned to complete tasks only for a few times and under a

time restraint that at times might of made them accidentally not follow part of the

procedure or not maintain the controlled variables. Materials especially may of caused

some of the errors since a big volume of people were assigned to use them and might of

forgotten to follow proper protocols. The environment was in a classroom lab with

automatic air conditioning, which may have varied at times trying to keep a constant

temperature. For example if a trial was under a vent while the air was blowing through, it

would have different results that a trial that was not under a vent. Since other groups were

working nearby the trials, air from blow dryers could have traveled to the trial and

impacted the results.

Improvements:

Although the results did come in favor of the original hypothesis that does not

make the way our experiment handled professionally satisfying. There are many ways we

could have improved the experiment. For example, an isolated environment where less

factors could affect transpiration, would have made it easier to have clear results. Also

control variables need to be coordinated through the different groups that were

conducting the trials. Some data seemed to be in different units and could not be

deciphered. Also, there seemed to be many extraneous results that may indicate error on

someones part. Most of all, the P-value and the T-value need to be listed in the

transformed data section of the data, which could help us confirm a solid conclusion.


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Works Cited


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Howard Perlman, Howard. "The Water Cycle: Transpiration." The Water Cycle (Water

Science for Schools). 13 Aug. 2008. USGS.

.

Janes, B. "Effect of Carbon Dioxide, Osmotic Potential of Nutrient Solution, and Light

Intensity on Transpiration and Resistance to Flow of Water in Pepper Plants1."

Plant Physiol 45 (1970).

Ritter, Michael. "Transpiration." The Physical Environment. 21 July 2006.

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humidity’s effect on transpiration

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