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Lab # ___ Transpiration. Text Pages: 746-748. 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.

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Lab # ___ Transpiration

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lab transpiration

Lab # ___ Transpiration

Text Pages: 746-748

procedure i
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??)
procedure ii
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

determining transpiration rate
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 section’s 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
determining transpiration rate ii
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.
data collection organization
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
analysis conclusion
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.