Zebrina Leaf and a Wet Mount
Purpose: The purpose of this lab investigation is to introduce the student to the technique of preparing a wet mount. As part of the exercise the student will examine the surface cells on the underside of a leaf.
Materials and Methods: For this lab, the student will require a microscope, lens paper, clean glass slides, cover slips, a dropper, clear fingernail polish, and the plant called Zebrina. The student should have completed the lab on the care and use of the compound light microscope.
Experiment: Obtain a leaf from Zebrina and paint the underside of the leaf with clear fingernail polish. Allow the polish to dry. Now peal a small strip of the dried fingernail polish from the leaf. You may have to break the leaf to free the polish. Apply the sliver of finger nail polish to a clean glass slide. Flatten the polish strip out on the slide, add a drop of water, and then lower a cover slip over the preparation. (Lower the cover slip by first placing one edge against the drop of water at about 45 degrees.) Obtain a microscope and locate the cell imprints on low power, but make additional observations using the high power objective. Be sure to adjust the lighting with the iris diaphragm. Make a sketch of what you see in the space below:
Conclusion: The large cells are called epidermal cells. Smaller sausage-shaped cells that are in pairs are called guard cells. The space between them is called a stoma (stomata, pl.).
What do you think is the purpose of these stoma?
Had you checked the topside of Zebrina, you would not have located guard cells or stoma. Why are these arranged on the lower side of the leaf?