Measuring Stomatal Density Lab Report

Measuring Stomatal Density

Materials:

Two sets of white oak leaves Microscope slides Clear nail polish

Clear wide packing tape Sharpie Lens paper

Procedure:

The following steps are to be done with white oak leaves from two sample groups.

1. Apply a fairly thick layer of clear nail polish to an area about 1 cm2 on the underside of a leaf from each of the two sample groups, taking care to avoid leaf veins. Allow several minutes for the polish to dry.

2. Cut a 2-3 cm piece of clear packing tape and fold down one corner for a “handle.”

3. Place the piece of tape over the nail polish and press down firmly with your thumb.

4. Using the “handle,” pull the tape from the leaf. You have just created a cast.

5. Tape your peeled impression to a clean microscope slide and trim off the excess tape. Use the sharpie to label your slide (name and sample group 1 or 2).

6. Use the microscope techniques you learned last week to bring the leaf impression into focus under high power. Position your slide so that there are no veins in your field of view.

7. Count the number of stomata in your field of view and record the number in your data table.

8. Repeat steps 6-7 two additional times, repositioning the slide to a new field of view each time.

9.. Using the field-of-view area that was calculated last week, find the density of stomata (stomata/mm2) for each counting. Record the densities in your data table.

10. Go to http://www.graphpad.com/quickcalcs/ttest2 to run an unpaired t test to determine if the difference in your means is significant.

Results:

Table 1: Stomatal Density of White Oak Leaves from Sample 1(INNER LEAVES)

	Stomata/field	Area of microscope field of view under high power (mm2)	Stomatal density (Stomata/mm2)
Field of view #1	102	.159 mm2	102/.159 mm2 = 641.51/mm2
Field of view #2	103	.159 mm2	103/.159 mm2 = 647.80/mm2
Field of view #3	74	.159 mm2	74/.159 mm2 = 465.41/mm2
Field of view #4	104	.159 mm2	You finish the rest of the calculations
Field of view #5	73	.159 mm2
Field of view #6	86	.159 mm2
Field of view #7	59	.159 mm2
Field of view #8	69	.159 mm2
Field of view #9	79	.159 mm2

Table 2: Stomatal Density of White Oak Leaves from Sample 2 (UPPER/OUTER LEAVES)

	Stomata/field	Area of microscope field of view under high power (mm2)	Stomata/mm2
Field of view #1	91	.159 mm2	Calculate these densities just as in the table above
Field of view #2	97	.159 mm2
Field of view #3	60	.159 mm2
Field of view #4	126	.159 mm2
Field of view #5	138	.159 mm2
Field of view #6	99	.159 mm2
Field of view #7	112	.159 mm2
Field of view #8	122	.159 mm2
Field of view #9	115	.159 mm2

Table 3: Mean, Standard Deviation and SEM for two sample groups

	Sample group 1	Sample group 2
Number in sample (N)
Mean
Standard deviation (SD)
Standard error of the means (SEM)

Table 4: Statistical Analysis

t value
Degrees of freedom (df)
Standard error of difference
Two-tailed P value
Mean of Group One minus Group Two
95% confidence interval of this difference

Conclusion and Discussion

1. Is the difference between the mean stomatal densities of your two sample groups considered to be statistically different?

2. Why might the stomatal densities of your two sample groups be different?

What to submit: 1) this completed form; 2) printout of your Graphpad analysis; 3) answers to the two Conclusion and Discussion questions above (word processed in Times New Roman with size 12 font and single spacing).