Pharmacognostic Importance of Epidermis

Leaves offer diagnostic characteristics which serve in

quality control of leaf drugs

  Shape, size and wall structure of the epidermal cells

Straight –walled epidermal cells are found in medicinal plants such as coca and Senna leaves

Wavy-walled epidermal cells are in found in Datura stramonium, Hyoscyamus niger and Atropa belladonna.  

Form, distribution and relation to epidermal cells of the stomata

  Stomata are classified on the basis of subsidiary cells into; ·       

  Anomocytic Stomata

o   When cells surrounding the stomata resemble other epidermal cells ·        

Anisocytic stomata

o   Stoma is surrounded by three or four subsidiary cells one of which is markedly smaller than others ·        

Paracytic stomata

o   Two subsidiary cells with their long axes parallel to the pore ·   

      Diacytic stomata

o   Two subsidiary cells with their long axis at right angle to the pore of the stomata

o   Variations among anisocytic, paracytic and diacytic types of stomata: · 

        Actinocytic type

o   Subsidiary cells are arranged along the radii of a circle

Form, distribution and abundance of epidermal trichomes

 Trichomes offer physical and chemical protection from microbes, aphids and insects.

Types of trichomes are characteristic of a plant family or genus

  Clothing trichomes –cover surface of the leaf

  Glandular trichomes –may be unicellular or multicellular (they store ergastic/drug substances) ·         Multicellular trichomes may be;  

o   Uniseriate, biseriate, multiseriate or complicated branched structures  

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