Sample Lab Activity Note
Activity Note – Observing Leaf Stomata
Introduction:
Photosynthesis is the process that green plants use energy from the sun to convert carbon dioxide from the air and water from the plant cells to make glucose, which the plant uses as food, and gives off oxygen gas.The carbon dioxide and oxygen gets into and out of the leaf through the small pores on the bottom of the leaf called stomata. The actual opening into the leaf is called a stoma, and the two cells that can change shape to open and close the stoma are called guard cells.
In this activity, we are going to make a nail polish impression of leaf stomata and observe the stomates under high power magnification. The stomate density (how many stomates are in every square millimeter) can be calculated using the formula:
Stomate density = number of stomates in high power view / 0.2 mm
Materials and Procedure:
Refer to Annex A, class handout “Observing Leaf Stomata”
Data Collection and Analysis:
Below is a picture taken from the microscope digital camera of our leaf impression at 400 x magnification.
We observed 9 stomata in our field of view. The stomata density using the formula given was calculated to be 45 stomates per mm^2.
Conclusion:
The method of obtaining a stomata impression from nail polish and tape worked very well. It was very easy to see the stomates. A stomata density of 45 stomates/mm^2 was quite large. It makes sense that there would be a lot of stomates in the leaf, since the leaf is designed to perform photosynthesis. If there weren’t enough stomates, then the carbon dioxide and oxygen gases would not be able to get into or out of the leaf very well. It would be interesting to compare stomata density with other leaf species, or leaves that are in the shade versus the direct sun.
