Stomatal density refers to the number of stomata present in a specific area of a leaf, and it is typically measured using a microscope.

To determine the stomatal density of a leaf, you first need to obtain a clear imprint of its surface. This can be accomplished by applying a layer of clear nail varnish to a small section of the leaf, allowing it to dry completely, and then carefully peeling it off. This process will yield a clear impression of the leaf’s surface, including the stomata.

Next, place the nail varnish imprint onto a microscope slide for examination. Under the microscope, you should be able to observe the stomata, which appear as tiny openings resembling mouths or pairs of sausages.

To calculate the stomatal density, count the number of stomata within a defined area. This measurement can be facilitated by using a graticule, a small measuring device that fits into the eyepiece of the microscope. The graticule features a scale that enables you to quantify the area under observation.

Once you have counted the number of stomata in a known area, you can calculate the stomatal density. This is typically expressed as the number of stomata per square millimeter. For instance, if you count $20$ stomata in an area of $1 \, \text{mm}^2$, the stomatal density would be $20 \, \text{stomata/mm}^2$.

It is crucial to take multiple readings from different regions of the leaf and calculate an average to obtain a more accurate measurement of stomatal density. This is important because the number of stomata can vary significantly across different parts of the leaf.