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 square mm.
Calculating the area
In the illustration, the diameter of the field of view of the microscope is 0.40 mm.
Its area can be calculated using formula πr2
Where π:= 3.14 r = radius of the field of view
If the diameter of the field of view is 0.40 mm, the radius is 0.20 mm.
Area = πr2 = 3.14 x 0.20 x 0.20 = 0.13 mm2
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 mm 2 is:
The density of stomata is therefore 92 stomata per mm2.
Using the same microscope, what is the density of stomata 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 therefore 192 per mm2.