Pharmacognosy 1 Lecture 1: Flowers (Introduction) PDF

Pharmacognosy 1 (PHG 1202) Flowers (Introduction) Lecture 1  Pharmacognosy-1 1. Overall Aims of Course Upon successful completion of this course, the students should be able to illustrate with details the macro- and micrmorphological characters of medicinal plant...

Pharmacognosy 1 (PHG 1202) Flowers (Introduction) Lecture 1  Pharmacognosy-1 1. Overall Aims of Course Upon successful completion of this course, the students should be able to illustrate with details the macro- and micrmorphological characters of medicinal plants composed of flower, bark, wood seeds & fruits. The students will also have information about pharmacognostical drugs and mention the active constituents and uses of some medicinal plants.  Course contents 1. Flowers 2. Barks and gall 3. Wood 4. Seeds 5. fruits 1- FLOWERS  By the end of this lecture you will be able to: Define flower. Understand the development of flowers and its role for the plant. Mention different parts and types of the flower. Compare between different types of flowers. Define inflorescence and mention its types.  Definition Flower is the reproductive structure found in flowering plants (angiosperms). The biological function of a flower is to mediate the production of fruits and seeds (propagation of the plant). Flowers may help in the identification of unknown plants. Plant Life Cycle  Parts of flower A typical flower is formed of four sets of floral leaves arranged on receptacle. 1- The calyx composed of sepals 2- The corolla composed of petals **When calyx and corolla are alike they are known as perianth (tepals). 3 The androecium composed of stamens (Anther + filament) 4 The gynaecium composed of carples (Stigma + style + ovary) **Bract: is a leafy structure from the axis of which the flower arises. **Involucre: is a group of bracts arranged in one or more whorls surrounding a group of flowers ** The calyx and corolla are considered non-essential floral parts, while both androecium and gynoecium are essential floral parts  Parts of the Flower (1-Receptacle) It is the swollen or expanded apex of the flower stalk or pedicel. It bears all the floral parts on it.. When the receptacle is elongated below the calyx and ovary, it is called Hypanthium (e.g. Clove).  Parts of the Flower (2-Calyx) Gamosepalous Polysepalous It is the outermost whorl of the floral parts, and composed of a number of sepals. Color: Always green, but some times brightly colored. Function: Protects the essential floral parts especially in the bud stage. Types: A- Polysepalous calyx: When the calyx consists of free sepals. B- Gamosepalous calyx: When the calyx consists of united (fused) sepals forming a tube with free apical tips in the form of lobes, segments or teeth, the number of which indicates the number of sepals.  Epicalyx In some flowers the sepals are stipulate and each pair of stipules fuse together forming an outer sepal-like structure called epicalyx.  Parts of the Flower (3-Corolla) Gamopetalous Polypetalous It is the second floral whorl after the calyx, and composed of a number of petals. Color: Usually brightly colored. Function: Attract the pollen grains carrying insects (Pollinators), and also protects to some extent the essential floral parts. Types: A- Polypetalous corolla: When the corolla consists of free petals. B- Gamopetalous corolla: When the corolla consists of united (fused) petals forming a tube with free apical tips in the form of lobes, segments or teeth, the number of which indicates the number of petals.  Parts of the Flower (4-Androecium) Didynamous stamens It’s the male sexual organ of the flower. It consists of one or more whorl of stamens. The complete stamen consists of a filament bearing an apical swollen structure called the anther which is responsible for the production of pollen grains. Types: 1 According to the number of stamens: a.Defenit: when the number of stamens is few and can be counted. Monandrous: one stamen – Diandrous: 2 stamens – Triandrous: 3 stamens – Tetrandrous: 4 stamens (Didynamous: if they were 2 long and 2 short) b.Indefenite: when the numbers of the stamens are numerous and can not be counted. (Polyandrous).  Parts of the Flower (4-Androecium) Tetradelphous Syngenesious Polydelphous 2- According to the cohesion of the stamens (if the stamens are fused): a. Monodelphous: when the filaments are fused in one group. b. Diadelphous: when the filaments are fused in 2 groups. c. Tridelphous: when the filaments are fused in 3 groups. d. Polydelphous: when the filaments are fused in several groups. e. Syngenesious: when the filaments are free, but the anthers are fused.  Parts of the Flower (4-Androecium) Epipetalous Gynandrous 3- According to the adhesion of stamens with other floral parts: a. Epipetalous: Adhesion occurs between stamens and petals. b. Episepalous: Adhesion occurs between stamens and sepals. c. Gynandrous: Adhesion occurs between stamens and gynecium.  Parts of the Flower (Pollen grains) They are very minute particles produced by the anther. They have different shapes and sizes and are very charecterstic for each plant. Its wall consists of 2 layers, exine followed by intine. The surface of the pollen grains may be smooth, spiny or granular. **The stamens may be sterile i.e. not producing pollen grains and are termed staminoid  Parts of the Flower (5-Gynaecium) Gynaecium is the female sexual organ, and composed of one or more carpels (pistils). It may consists of one carpel: Mono-carpellary – 2 carpels: Di-carpellary and so on… Types: a. Apocarpous: when the carpels are free. b. Syncarpous: when the carpels are united. Each carpel consists of: Stigma: The apical part of the carpel, swollen, sticky, and covered with papilla. Ovary: Enclosing one or more ovules arranged on the placenta. Style: a stalk connecting the stigma to the ovary.  Parts of the Flower (Gynaecium) Hypanthium Inferior ovary Superior ovary Types of ovary according to insertion of floral parts: a. Superior: floral parts are inserted on the receptacle below or at the same level as the ovary. b. Inferior: floral parts are inserted on the top of the ovary.  The Inflorescence Flowers: solitary or aggregates Main axis of the inflorescence is called the rachis, while the stalk is called pedicel.  Kinds of inflorescence Inflorescence Racemose Cymose Indefinite, monopodial branching Definite, sympodial branching The youngest flower at the apex or Shows the youngest flower at the base or outside. at the center. The oldest at the The oldest flower at the apex or at the center It base or outside includes simple cyme and compound cyme. Racemose inflorescence Cymose inflorescence  Capitulum Disk florets Ray florets Capitulum = (Flower head): axis is swollen conical on which sessile flowers (florets) are inserted (e.g. chamomile). Types of florets: a. Disk (tubular) florets: The central florets which have tubular corolla. b. Ray florets: The marginal florets which have strap-like corolla.