A traditional method for determining stomata distribution in a plant is to make an epidermal impression using a clear nail varnish; in the absence of nail varnish, use Germolene New Skin or a water-based varnish, available at do-it-yourself shops. A microscope, a leaf, clear tape, a microscope slide, and nail varnish or alternate material are required for the process.
Coat the surface of the leaf with the nail varnish. Wait for the nail varnish to dry, then use clear tape to peel the dried layer of nail varnish from the leaf. Use the tape to attach the epidermal impression to a slide. If the epidermal impression peels off directly, use water to attach it to the slide. Place the slide with the epidermal impression under the microscope and count the number of stomata present.
If an eyepiece graticule is available, work at a lower magnification, and count using the number of stomata within different squares as replicates. Without the eyepiece, use a higher magnification to count a number of different fields at a time.
Be sure to get enough counts to create sufficient data for a statistical analysis. Calculate the area of the leaf using a micrometer to adjust the numbers to the size of the field of view. The result is the number of stomata per square millimeter.
In some instances, the solvent in the nail varnish may damage the leaves and cause them to turn brown, preventing the leaf from producing an impression.