# Lab # ___ Transpiration

Document Sample

```					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
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.
Suggested Data Table (p. 1)
Condition   Initial   5 min.   10 min. 15 min.   20 min.   25 min
30 min.
Room        0.55      .60      .67     .74       .80
Mass:

Wind        0.0       0.0      0.005   .01       .014
Mass:

Mist        0.165     0.195    0.218   0.231     0.242
Mass:

Light       0.0100    0.0100 .3400     .3450     .3500
Mass

Vacuum      0.20      .205     .211    .219      .226
Suggested Data Table (p. 2)
Condition   Initial   5 min.   10 min. 15 min.   20 min.   25 min
30 min.
Room        .695      .705     .715    .719      .725      .732     .741

Wind        0         .017     .026    .035      .043      .055     .063

Mist        .458      .475     .480    .483      .484      .484     .485

Light       .148      .154     .163    .173      .188      .202     .216

Vacuum
Suggested Data Table (p. 5)
Condition   Initial   5 min.   10 min. 15 min.   20 min.   25 min
30 min.
Room

Wind

Mist

Light

Vacuum
Suggested Data Table (p. 6)
Condition   Initial   5 min.   10 min. 15 min.   20 min.   25 min
30 min.
Room

Wind

Mist

Light

Vacuum

```
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
 views: 29 posted: 11/23/2011 language: English pages: 11