Students will investigate questions concerning the number of stomata on plant leaves. The student may generate a hypothesis if desired. Questions include:
Is the stomatal density the same on the top or bottom leaf surfaces?
Do house plants have a higher stomatal density than outside plants?
Clear fingernail polish/sealer, plant leaves, microscopes, slides, transparent tape, transparent ruler.
- Students 'paint' a leaf surface with fingernail sealer. A small area is all that is required - smaller than a cover slip. A thin coating is sufficient.
- Let the polish dry, usually < 5 minutes.
- Apply a piece of transparent tape to the sealer and quickly lift up to remove the sealer from the leaf. The sealer bears an imprint of the leaf surface showing the epidermal cell boundaries and the stomates.
- The taped imprint is applied to a glass slide. No cover slip is needed. Typically the slide is viewed at 400x.
- Less sophisticated students can count the number of stomates within the field of view (FOV).
- More sophisticated students can calculate the area of the FOV by using the transparent ruler with the scan objective and adjusting the area by the proportion of magnification. This will yield a stomate density.
- Note some plants have LOTS of stomates in the FOV. Students may have to do some sub-sampling (count stomates in ¼ of the FOV) for their estimates.
- Multiple FOVs on the taped imprint can be used for repeated trials or imprints from other leaves or plants used.
Record plant used, numbers of stomata, FOV, calculations and stomatal density. Sketch a typical stomate with surrounding epidermal cells.
Use your data to answer the question.
Stomata Activity Data Sheet
Plant name __________________________________________________
|Magnification||Method||FOV||FOV area (show calculations)|
|10 * 4 = 40x||Measured||Area = πr2 =|
|10 * 10 = 100x||Measured|
|10 * 40 = 400x||Calculated|
|Manipulated Variable||Magnification||Stomata count||Density (show calculations)|
|count / area =|