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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 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. ***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 • 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 • 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 • 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 • 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 • 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.
