Pharmacognosy 1: Introduction to Medicinal Plants

Aims of the Course

• The course focuses on cultivated and wild medicinal plants used in pharmaceuticals, cosmetics, and the food industry.
• It deals with botanical drugs of leaves, flowers, barks, woods, and unorganized origin.

Course Content

• Leaves
• Flowers
• Barks
• Woods
• Unorganized drugs

Assessments

• Class work: 5 marks (5%)
• Midterm exam: 10 marks (10%)
• Practical exam: 25 marks (25%)
• Final written exam: 50 marks (50%)
• Oral exam: 10 marks (10%)
• Total: 100 marks (100%)

Parts of a Leaf

• Leaf base: the part of the leaf directly attached to the stem
• Stipules: appendages at the leaf base
• Petiole: the part of the leaf between the blade and the base
• Leaf blade or lamina: the green, flattened part of the leaf used for photosynthesis

Types of Leaves

• Simple leaves: consist of one continuous blade
• Compound leaves: have a divided leaf blade called leaflets

Leaf Insertion

• Cauline: leaves arise on the main stem
• Radical: leaves arise from a reduced stem

Phyllotaxy

• The disposition of leaves on the stem
• Leaves are arranged on the stem in a definite manner characteristic for each species of plants

Types of Phyllotaxy

• Alternate: a single leaf arises from the node of a branch
• Opposite: two leaves arise from the node in opposite directions
• Decussate: opposite leaves at any one node are at right angles to those at the upper or lower node
• Whorled: three or more leaves arising from the node

Leaf Petiole

• Petiolated: when a leaf stalk or petiole is present
• Sessile: when the petiole is absent

Leaf Base

• Stipulate leaves: leaves with stipules
• Exstipulate leaves: leaves without stipules
• Stipules are small outgrowths that are typically leaf-like and present on the sides (one or both) of the base of a leafstalk

Base of Lamina

• Symmetric: the two halves of the lamina are identical
• Asymmetric: the two halves of the lamina are not identical
• Decurrent: when the base of a leaf continues for a distance along the stem

Lamina Shapes

• Linear: longer and slightly broader
• Lanceolate: shaped like a lance
• Oblong: more or less rectangular as in banana
• Ovate: egg-shaped
• Cordate: heart-shaped
• Obovate: reverse of ovate
• Obcordate: reverse of cordate
• Rhomboid: kite-shaped

Lamina Margin

• Entire: when the margin is smooth
• Serrate: margin with teeth pointed upwards
• Dentate: margin toothed, the teeth are pointed outward
• Crenate: margin toothed and the teeth are rounded
• Lobed or incised: when the margin is so much dissected that it can no longer be described simply as toothed
• Parted: with lobes cut ½ to ¾ the distance to the midrib

Apex of the Lamina

• Acute: when pointed and narrow
• Acuminate: when the apex is drawn out into a long tapering tail
• Obtuse: when the apex is broad angled and blunt
• Rounded: the leaf apex is broadly rounded
• Truncate: an apex that terminates abruptly in a nearly straight horizontal edge
• Retuse: when the obtuse apex is slightly notched

Venation

• Reticulate venation: a network-like pattern of veins
• Parallel Venation: the veins run parallel to one another

Simple Leaves

• Entire simple leaves have plain, rounded shapes without any projections
• Lobed leaves have projections of the blade with gaps between them
• Palmate leaves have lobes that radiate from a single point
• Pinnate leaves have lobes that are arranged along a central stalk

Compound Leaves

• Have a divided leaf blade called leaflets
• Types of compound leaves: palmately compound and pinnately compound

Pinnately Compound Leaves

• Paripinnate (even-pinnate): leaflets are borne in pairs along the rachis, ending with a pair of leaflets on either side
• Imparipinnate (odd-pinnate): a single leaflet is present at the anterior terminal end of the rachis