Appendix XI H. Stomata

(Ph. Eur. method 2.8.3)

STOMATA

There are several types of stomata (see Figure 2.8.3.-1), distinguished by the form and arrangement of the surrounding cells:

(1) The anomocytic (irregular-celled) type: the stoma is surrounded by a varying number of cells in no way differing from those of the epidermis generally,
(2) The anisocytic (unequal-celled) type: the stoma is usually surrounded by 3 subsidiary cells, of which one is markedly smaller than the others,
(3) The diacytic (cross-celled) type: the stoma is accompanied by 2 subsidiary cells, whose common wall is at right angles to the guard cells,
(4) The paracytic (parallel-celled) type: the stoma has on each side one or more subsidiary cells parallel to the long axis of the pore and guard cells.

STOMATAL INDEX

S
 = 
the number of stomata in a given area of leaf,
E
 = 
the number of epidermal cells (including trichomes) in the same area of leaf.

For each sample of leaf, make not fewer than 10 determinations and calculate the mean.

Figure 2.8.3.-1