Lab

1
Lab ___ Transpiration

• Text Pages 746-748

2
Procedure I

• Attach the water-filled syringe to the small
  tubing.
• Prime the potometer by adding water (slowly) with
  the syringe until the level of the water forms a
  bead on the top of the longer tubing side.
• check to insure that the tubing side is about
  ½ the distance up the pipet side.
• Using the scissors, gently cut a tapered plant
  stem form the plant. Try to find a stem that
  would fit snugly firmly into the tubing side of
  the stem.
• Insert the cut stem into the tubing.
• Remember you want an air-tight system so make
  sure that there are no air bubbles present.
• Dry the area at the base of the stem near the
  tubing
• Seal the area with petroleum jelly.
  (Hypothesis??)

3
Procedure II

• Allow the potometer to equilibrate for 5 minutes.
  Note the level will go down and should slowly
  stop.
• Once it is equilibrated, gently press the plunger
  of the syringe until the water level reaches zero
  on the pipet. If it leaks add more jelly and
  start at a lower level on the pipet for your
  initial reading.
• Record your initial reading (0 ml) and monitor
  the potometer and record your data every 5
  minutes for 30 minutes.
• We will discuss the theory behind transpiration
  and begin our discussion on photosynthesis.
• Discuss -Leaf surface area determination (2
  ways)
• -Sources of Error

4
Determining Transpiration Rate

• At the end of the experiment cut off all the
  leaves from your stem, blot off excess water and
  take the mass of the leaves.
• Mass of all the leaves g
• Two ways to figure out the surface area
• Leaf trace method with graph paper
• Leaf mass method (we will do)
• Cut a 1 cm2 section from one of the leaves.
• Take the mass of this section g
• Multiply the sections mass by 10,000 to convert
  to m2. Leaf surface area m2
• Divide the total mass of leaves (grams) by the
  mass per square meter to determine the leaf
  surface area
• Record the value m2

5
Determining Transpiration Rate II

• Calculate the water loss per square meter of leaf
  surface area by dividing the water loss at each 5
  minute reading by the surface area you
  calculated.
• Place your calculated values in a table.
• Water loss at 0, 5, 10, 15, 20, 25, 30 (lab data)
• Water loss per m2 at same intervals
• Overall class averages will be determined.

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Data Collection Organization

• Plant species
• Table I All five conditions and 5 minute
  intervals
• Mass of all leaves g
• Mass of 1 cm2 section g
• Mass of all leaves (g) x 1 cm2 x
  (1 m 2)
• mass of section (g) (104 cm)
• Total Leaf surface area m2
• Table II Water loss
• Cumulative water loss / m2 for each condition
• Transpiration rate water loss/ m2 / minute
• Plot Graph all five conditions

7
Analysis Conclusion

• Do Question 1-5. Be sure to include the vacuum
  condition to all responses
• On the back Briefly state if your hypothesis is
  supported by this data or not and comment on
  sources of error that could have been a factor.

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Suggested Data Table (p. 1)
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Suggested Data Table (p. 2)
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Suggested Data Table (p. 5)
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Suggested Data Table (p. 6)