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# What is Plant Transpiration? (page 2)

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Author: Michael Calhoun

### Experimental Procedure:

1. Fill two test tubes approximately three-fourth full of water. Stand both test tubes in an empty metal can.
2. To control for water evaporation place sheets of clear plastic wrap over the mouths of one of the test tubes and seal with masking tape.
3. Use the plant stem to poke a hole into the test tube so that it stands upright in the tube. Seal around the hole with tape.
4. Use a ruler to measure the height of the water in each test tube. Be sure to hold the test tube level, and measure from the waterline to the bottom of the curve at the bottom of the test tube. Record these measurements in a data table similar to one shown labeled "Initial."
 Time Test tube with plant (A) Test tube without plant (B) Initial After 15 min After 30 min After 45 min After 60 min
1. Wait 15 minutes, and measure the height of water in each test tube again. Record these measurements in the data table.
2. Reap step 4 three more times. Record the measurements each time.
3. Wait 24 hours, measure the height of the water in each test tube. Record these measurements in the data table.
4. Using the data in the table plot a bar or line graph of the Rate of Transpiration by showing the time (min) along the X-axis verses the water level height (mm) in the test tubes along the Y-axis.
5. Calculate the rate of transpiration by using following operations:

Test tube with plant:

Initial height - Overnight height = Difference in height of water (A)

Test tube without plant:

Initial height - Overnight height = Difference in height of water (B)

Water height difference due to transpiration: Difference A - Difference B = Water lost due to transpiration

 Initial amount of water Amount of water left after 24 hours Amount of water lost Tube with plant branch Tube without branch
6. To calculate the rates of transpiration and evaporation per hour use the following formulas: Amount of water lost ÷ 24 hours = ________ water transpired /hour Amount of water lost ÷ 24 hours = ________ water evaporation/hour

Terms/Concepts: Transpiration; evaporation; evapotranspiration; stomata; solar radiation

References:

Books:

Title: How Do Plants Grow?

Author: Melissa Stewardt

Publisher: Cavendish, Marshall Corporation ISBN-13: 9780761433668 and ISBN: 076143366X

This five-chapter 32-page book explains the basics of plant photosynthesis. In the chapter "What Plants Need to Grow," the author describes how plant leaves collect energy from the sun and release water and oxygen to the atmosphere, while the roots absorb water and minerals from the soil this action makes transpiration possible.

Links to related sites on the web

Title: Transpiration

Title: Transpiration

Title:Transpiration Lab

NOTE: The Internet is dynamic; websites cited are subject to change without warning or notice!

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