Apparatus- Compound microscope, camera lucida, Drawing board ,chloral hydrate solution, Glycerine ,water, etc

Principle:

Stomal index is the percentage which the no. of stomata form to the total number of epidermal cells each stoma being counted as one cell. Stomatal index can be calculated using the following equation.

S.I = (stomatal index) = S/E+S into 100.

Where,

S.I.= stomatal index

S = No. of stomata per unit area.

E = No. of epidermal cells in the same unit area.

Where stomata number varies considerably with the age of the leaf & due to changes in environmental conditions, stomatal index is relatively constant, & therefore of diagnostic significance for a given species It is employed for the differentiation of allied or closely related same species genus in air dried as well as fresh conditions.

Procedure:

1) Clear the fragments of leaf from middle of lamina by boiling with chloral hydrate solution or alternatively with chlorinated soda peel out upper & lower epidermis separately by means of forceps.

2) Prepare the mounts of lower & upper epidermis separately in glycerine water.

3) Draw squares of known dimensions by means of a stage micrometer & camera lucida on a drawing paper.

4) Replace the stage micrometer by cleared leaf preparation Focus under the same magnification & trace the epidermal cells & stomata by looking through the microscope when a super-imposed image of the leaf is seen at the same time count the number of epidermal cells & stomata within the square. A cell being counted if half its area lies within the square provided 2 adjacent sides are considered for purpose of calculation.

5) Calculate the stomata number i.e number of stomata per sq.mm of leaf preparation calculate stomatal index.

Calculate the result as follows

Where S = the number of stomata in a given area of leaf ; and

E = the number of epidermal cells (including trichomes) in the same area of leaf.

For each sample of leaf make not fewer than ten determinations and calculate the average index