Scientists use sampling and counting techniques to investigate the distribution of stomata on leaves. They count stomata to investigate:
Below are two methods with which stomata can be counted.
The density of stomata on a leaf is recorded per unit area, usually the number per sq mm.
In the illustration, the diameter of the field of view of the microscope is 0.40 mm.
Its area can be calculated using formula
= radius of the field of view
If the diameter of the field of view is 0.40 mm, the radius is 0.20 mm.
The number of stomata in the field of view is 12.
The area of the field of view is 0.13 mm2.
Therefore, based on this single count, the density of stomata over 1 mm2 is:
The density of stomata is therefore 92 stomata per mm2.
Using the same microscope, what is the density of stomata per mm2 based on the following counts?
24 23 22 27 28 25 26 24 26 25
The average count =
The mean count = 25.
The field of view is 0.13 mm2.
Therefore, the number of stomata over 1 mm2 =
The density of stomata is 192 per mm2.