Pharmacognosy II Lecture Notes Fall 2024/2025 PDF

Course Title: Pharmacognosy II Course Code: PHG 213 Week number: 9 Lecture number: 7 Lecturer: Dr. Hanan Samir Marzouk Fall 2024 / 2025  Subterranean Organs (Under ground Organs) Subterranean stems Subterranean roots as rhizomes, corms, as roots an...

Course Title: Pharmacognosy II Course Code: PHG 213 Week number: 9 Lecture number: 7 Lecturer: Dr. Hanan Samir Marzouk Fall 2024 / 2025  Subterranean Organs (Under ground Organs) Subterranean stems Subterranean roots as rhizomes, corms, as roots and bulbs and tubers root tubers  The Main Characters of Subterranean Organs:  They are storage organs, they are full of reserve food materials as: Starch in Filixmas and Rhubarb Sugars in Gentian Inulin in plants belonging to Family Asteraceae (Compositae)  They are devoid of chlorophyll. I- Roots  I- Roots The root is the portion of the plant axis which grows vertically downwards into the soil, it never develops leaves, usually bearing no buds and the growing point is covered by a special tissue called root-cap or calyptra. It does not show nodes and internodes and is characterized by the absence of chlorophyll. Roots bear only one kind of lateral appendages namely branches which are similar in construction and general characters to the main root; the origin of the branches is described as "endogenous", characterized from those of the stem "exogenous", because the growing point of the root branches arise in the outer most layer of the stele, (Pericycle). They arise opposite either to the protoxylem or to the conducting parenchyma separating the xylem group from the phloem groups. The lateral roots occur, therefore, in rows either of the same number as that of the primary xylem groups or twice this. Adventitious roots arise from the pericycle or endodermis of the stem.  Types of Roots  Primary root  Fibrous root e.g. Senega e.g. Grass  Secondary root  Aerial roots e.g. Krameria e.g. Ficus, Hedera  Adventitious root  Respiratory roots e.g. some plants growing in e.g. Ipecacuanha water logged soil.  Prop root  Storage roots (root e.g. Maize tubers) e.g. Belladonna, Umbelliferous, Calumba  Primary root Secondary root Fibrous root Tap root Storage root (root tubers) Types of Roots: Primary roots: Developing into tap-root as in senega and Belladonna. Secondary root: or lateral as in Krameria. Adventitious roots: Arising neither from the main root nor from its branches. They usually arise from the stem as in Ipecacuahna. Prop root: they are adventitious roots growing from the stem, nearly above the soil and extending diagonally into the ground e.g. Maize. Aerial root: they are adventitious either hanging in the air, e.g. Vanilla or growing down to anchor in the ground, e.g. Ficus bengalensis, or climbing and then called tendrils, e.g. Hedera or for absorbing water from the air, as in air-roots of Orchis. Fibrous roots: Very slender roots as in grasses. Storage roots: Swollen with reserve food material. Swollen primary root occur in Belladonna and Carrot. Swollen secondary roots occur in Asafetida. Swollen adventitious roots occur in calumba, Ipecacuahna and Jalap. These which are very swollen e.g., carrot are called root tubers, tuberous or tuberculated roots.  Mention the type of root General Scheme for Description of Roots Condition: 1) Dry or Fresh 2) Entire or sliced longitudinally or sliced transversely 3) Peeled Shape and Size: Cylindrical or Subcylindrical or Teret or Twisted or Obconical or Fusiform or Napiform Type:  Structure of Roots Histology or Microscopical Characters  I- Young Roots Monocot Root Dicot Root  II- Old Root cork Phelloderm Remember: Secondary structure occurs only in dicots & Gymnosperms  The following T.S. is of: a) Young monocot root drug b) Old monocot root drug c) Young dicot root drug d) Old dicot root drug Activity I Mention the Type of the Followings  II- Subterranean Stems The underground stem is fundamentally a mean of propagation of the plant as well as a storage organ. It is characterized from root by bearing scale leaves, axillary buds, adventitious roots and by having the growing point (bud) protected by scale leaves but not by root-cap. Internally it never shows a central solid mass of xylem and in dicots always having parenchymatous pith. Distinction from Aerial Stem  It bears scale leaves not foliage leaves.  It bears adventitious roots arising generally from the nodes. Direction of Growth Horizontally Vertically Obliquely Types of Subterranean Stems Rhizome Stem tuber e.g. Rhubarb e.g. Potato Root stock Corm e.g. Colcasia, e.g. Senega Colchicum Sobole Bulb: e.g. Couch grass a. Scaly e.g. Allium Sucker b. Tunicated e.g. Mentha, Rose e.g. Squill  Scaly bulb Corms Stem tuber Tunicated bulb Rhizome Sucker Rhizome: with nodes and short or long internodes, terminal buds and aerial shoots are also present. They are usually thick and perennial. Sobole: a kind of rhizome which is long, thin rapid in growth and with long internodes Sucker: It is a branch growing under the ground arising from the stem as in Mentha or from the top of the root as in Rosa. Stem tuber: A swollen underground stem or part of stem, usually its tip. It differs from root tuber by bearing small scales and buds e.g. potato. It is full of food materials and serving for vegetative propagation. Corm: A shortened swollen erect underground stem, most commonly the base of the stem, covered with brown scale- leaves arising at the nodes and having usually a large apical bud and small axillary ones. The daughter corm is produced below the large bud as in colocasia or at its side as in Colchicum. Corm differs from stem tuber by having enveloping scales and flowering bud. In distinction from rhizome, it is formed of one season growth, the previous season corm having usually disappeared. Bulb: Underground stem, reduced to a small flattened disc, crowned with crowded fleshy scaly leaf bases where food materials are stored and adventitious roots arise from the base of the bulb e.g., Scilla. Stolon: It is an underground stem, it travels near the surface of the soil e.g Liquorice Rootstock: It is a vertical rhizome, the internodes are short and the surface has ring-shaped leaf scars often transverse wrinkles due to shortening to keep the crown at the ground level e.g., Gentian. General Scheme for Description of Subterranean Stems Condition: 1) Dry or Fresh 2) Entire or sliced longitudinally or sliced transversely 3) Peeled 4) Broken peices Shape and Size: Direction of Growth Mode of Branching Kind  Structure of Subterranean Stem 1. The tegumentry layer: (outer protective layer) a. Epidermis b. Cork 2. The cortex 3. The Endodermis 4. The vascular bundles: a. open b. closed c. dictyostele  a) The subterranean stem can be distinguished (differentiated) from the root by: 1. The presence of radial vascular bundle & presence of pith 2. The absence of radial vascular bundle & presence of pith 3. The presence of radial vascular bundle & absence of pith 4. The absence of radial vascular bundle & absence of pith b) The followings are types of subterranean stems: 1. ………………………. 2. ………………………. 3. ………………………. 4. ……………………….  Mention the type of the following T.S. Activity II Mention the Type of the Followings  Difference between Root and Subterranean Stem Root Subterranean stem Morphologically 1. 1. 2. 2. 3. 3. Histologically 1. 1. 2. 2.  Homework  Differentiate between the Following: 1. Subterranean Organs & Other Plant Organs. 2. Subterranean Root & Stem 3. Young & Old root 4. Young monocot & dicot roots 5. Young & Old Stem