Pharmacognosy II PG303 Notes PDF

Pharmacognosy II PG303 1  Course Grades 20 marks Periodical exam 40 marks Practical exam 15 marks Oral exam 75 marks Final exam 2 3  Introduction to Seeds Definition: A seed is a plant part derived from fertilized...

Pharmacognosy II PG303 1  Course Grades 20 marks Periodical exam 40 marks Practical exam 15 marks Oral exam 75 marks Final exam 2 3  Introduction to Seeds Definition: A seed is a plant part derived from fertilized ovule, so it is a mature fertilized ovule that contains an embryo. Ovules are transformed to give seeds Ovary swells and enlarge to give the fruit (enclosing seeds) 4 5 6 7  Function of seeds 1. Ensure continuation and distribution 2. Facilitate transportation 8 Structure of the Ovule 9  Structure of the Ovule The mature ovule, consists of: 1. Integument or coats of the ovules → Testa (protection) 2. Micropyle: an opening for entrance of pollen tube 3. Nucellus→Perisperm (nutrition) 4. Endosperm → (nutrition) 5. Embryo sac or Megaspore(ovum) → Embryo 10 After fertilization Before fertilization Ovule Fertilization + Seed Pollen grain 11  Double Fertilization ❑ One sperm unite with egg cell ( to give the embryo, male + female, n+n = 2n) ❑ The other sperm unite with 2 central nuclei to give the endosperm (nutritive tissue, n+2n= 3n) 12  Radicle is the first part to emerge from Radicle is directed downwards while the developing cotyledons and shoot is directed upwards. embryo and Cotyledons are the fist leaves of the directed developing embryo. downwards 13 Fertilization and development of embryo Fertilization is defined as the fusion of the male nucleus with that of the egg. The pollen tube enters the ovule through the micropyle into the nuclear tissue and it enters the embryo sac. Fertilization & the development of the embryo causes the production of a number of changes in the ovule as well as in the ovary and sometimes in certain parts of the flower surrounding the ovary The ovule increases considerably in size forming the seed. The integuments by thickening and lignification of the cell walls give rise to the testa which protects the embryo against drying and injury. 14  The mature ovule -Nucellus: parenchymatous tissue enveloped by one or two integuments and have a small opening called micropyle. nucellus -Chalaza chalaza the basal part of the nucellus V.b -Embryo sac: from which the integuments contains eight or seven arise. funicle nuclei. - Funicle a small stalk at the chalaza end, by which the ovule is attached to the placenta, when it is detached, it forms a scar called hilum. 15 -Raphe formed by the fusion of the funicle with the integument for some distance. 16  Ovary nucellus 1ry endosperm nucleus Embryo sac, zygote or ovum 17 ⮚ After fertilization of the Ovule Outside Integument Testa (Coats) s √ Nucellus Perisperm √/X 2ry Nucellus Endosperm (Endosperm √/X Nucellus) Egg Embryo √ Inside 18 After fertilization The typical seed has: 1. Integuments form the seed coat (testa) with 2 and/or 3 distinctive marks 1. (Hilum) scar at attachment of ovule to funicle. (scar of different color) 2. (Micropyle) where there is no testa, through this openeing waters enter through it and radicle gets out of seed through it. 3. (And/OR Raphe) a vascular bundle running through the testa. It is formed by the fusion of the funicle with the integument for some distance it runs to reach chalaza where it branches to other tissues. (line / ridge / furrow) 2. Perisperm originate from nucellus. 3. Endosperm results from fusin of the polar nuclei and one sperm cell. 4. Embryo (from fusion of egg cell and the sperm ell) consists of radicle and cotyledons (one: monocot, two: dicot) Embryo Testa Perisperm Endosperm Always present Always present Present/absent Present/absent Develop in For protection nutritive nutritive whole plant Kernel: All tissues enclosed inside the testa Albuminous seed: contain endosperm ± perisperm Exalbuminous seed: consists of testa and embryo only 19 The outer surface of testa shows certain markings: 1. Hilum The scar left by removal of seed from its funicle or stalk 2. Micropyle The hole in the seed coat, present because coats at apex are not complete, serving to transport water during germination 20 3. Chalaza The place at the base of nucellus Nucellus where vascular bundles from funicle branch to enter different parts of Chalaza vascular bundles ovules Funicle 4. Raphe: The stalk of the seed grows on side of the ovule. It is line running from hilum to chalaza 21  Types of seeds according to the endosperm 1. Exalbuminous seeds (non endospermic) The zygote develops rapidly, resulting in an embryo surrounded by testa. Other contents like nucellus and embryo sac are absorbed e.g. beans. 22  2. Albuminous seeds (endospermic) A. The endosperm nucleus divides rapidly resulting in the endosperm which surrounds the embryo. In this case the seed is composed of the embryo and the endosperm is surrounded by the testa. (The nucellus absorbed) e.g linseed 23 B. The embryo and endosperm remain small and the cells of the nucellus are more active and develops to form the perisperm which surrounds the endosperm and embryo, or surrounded by the curved embryo. The perisperm is well developed e.g. cardamom 24  Types of seeds according to the endosperm Exalbuminous seeds Albuminous seeds (non endospermic) (endospermic) The perisperm The endosperm & endosperm develop develop 25 External appearance of a seed testa position of radicle micropyle hilum 26  TYPES OF OVULES 1. Atropous [orthotropous: Straight ovule , funicle, chalaza & micropyle on 1 straight line, no raphe 2. Anatropous: Ovule is inverted, raphe runs from one end to the other, micropyle adjacent to hilum & chalaza at distal end (it is inverted 180⁰) (1/2 circumference of the seed) 27 3.Amphitropous: ovule partly bent, micropyle & chalaza on a line at right angles to hilum, raphe = half distance from chalaza to micropyle, (1/4 circumference of the seed) * *in above mentioned types = nucellus is straight 4.campylotropous: ovule bent upon itself, funicle, chalaza & micropyle close to one another, no raphe & nucellus curved 28  Types of ovules: Atropous → no raphe Anatropous → raphe Amphitropous → raphe Campylotropous → no raphe 29  What is the type of the following ovules? Atropus Anatropus Campylotropus 30  A typical seed consists of Testa Kernel Embryo: developed from fertilized (egg) ovum Endosperm: surrounds the embryo and is developed from primary endosperm nucleus Perisperm: from the nucellus *The kernel is all the layers enclosed within the testa *Testa: Originated from the integuments. It protects the Kernel 31 tissues and is formed of one or two seed coats  Orthoplocous Types of embryo radical bents #1 cots & Cots. fold against Accumbent Midrib radical bents Incumbent e.g. Crucifirae Straight #2 cots. radical bents Family e.g. Linseed e.g. Leguminosae #1 cots (Black Mustard) Family (Fenugreek) Coiled Curved (concave) e.g. Solanaceae Family *To determine the type of embryo: L-cut then T-cut *Cotyledon is a modified leaf ⸫ has midrib 32  Types of outgrowth: During the formation of certain seeds, arises additional growths outside the integument or developed from the integuments. Different names are given to these outgrowths according to their origin and nature. 33  OUTGROWTHS OF TESTA 1.Arillus: from funicle or hilum, envelopes whole seed as in Cardamom ‫الحبهان‬ 2.Arillode: from micropyle, covers part or whole seed in nutmeg ‫ جوزة الطيب‬: *Mace arises from funicle & micropylar tissue, so= arillus or arillode 3.Caruncle: localised fleshy, from tissue in neighbourhood of micropyle & covering it, eg. Ricinus ‫نبات الخروع‬ 34 4.Strophiole: local enlargement over position of raphe, eg. Colchicum genus 5.Wing: membraneous extention, eg. Strophanthus genus 6.Tuft of hairs: **maybe sessile at the summit eg. Apocyanaceae family **borne on a slender stalk (awn) as in Strophanthus genus 35  The Testa type (Texture) Membranous (Almond) Leathery (Linseed) Hard (nutmeg) Woody (Calabar beans) Fleshy (Mangolia) 36  Outer surface of testa (Shape) Longitudinally striated Smooth (Almond) (Linseed) Pitted Papillosed (Digitalis) (Grain of paradise) 37 Reticulated Hairy (poppy) (Nux vomica) Rugged (Cardamom) 38  Microscopical characters 1- Testa and outgrowths , if present. 2- Perisperm: parenchyma cells containing starch) 3- Endosperm (parenchyma cells containing starch, 4- Embryo. protein, or fixed oils “Nutrient”) 5- Cell contents: starch, protein, fixed oils 39  ❖ The testa: Formed of one or two integuments. Four basic layers can be observed. Epidermis ± hypodermis, Sclerenchymatous layer (protection, rigidity) Nutritive or hyaline layer (usually collapsed cells because of food consumed) Pigment layer (responsible for color of seed) 40  Epidermis Hypodermis Sclerenchyma layer Testa Nutritive layer Pigment layer Endosperm Embryo 41 Reserved food material: ⚫Carbohydrates: Starch, cellulose, hemicellulose ⚫Fixed oil and protein (aleurone grain) 42 Types of aleurone grains: ▪ A. Aleurone grains are either simple in structure and consist of amorphous mass of protein enveloped by a protein membrane e.g. Leguminous seeds. OR consists of: ▪ B. a. Crystalloid b. Globoid Both the crystalloid and globoid are embedded in protein ground substance. 43  globoid Aleurone grains 44 ⚫The ground substance The ground substance in which the crystalloid, globoid., are embedded, it is quite amorphous and usually finely granular in appearance. ⚫The crystalloids Like the ground substance, of proteinoid matter. They assume a crystalline form but differ from true crystals in the inconstancy shown by their angles and in the fact that, under certain conditions, they swell. ⚫The globoids Rounded or ovoid in shape. They are insoluble in water and in dilute caustic potash, but are soluble in dilute acids and in solutions of various salts. ⚫Calcium oxalate ⚫Prisms, clusters and rosettes 45