Distribution of Stomata

There are two parameters normally used for expressing the distribution of stomata.

1. Stomatal frequency: The number of stomata per unit area.
2. Stomatal index: The ratio of number of stomata to the total number of cells per unit area.

Plants differ in their stomatal frequency. In monocots the upper and lower surfaces usually have the same frequency but in dicots the lower surface usually has a higher frequency than the upper surface. However, the frequency of stomata can change with the position of leaves on the plant.