Introduction To Leaves PDF

Crude drugs whose active constituents are localized in leaves The pharmacognostical study includes: 1. Botanical studies: to be able to identify the drug in its entire form and identify its powder. 2. Overview on the main active constituents, uses and side effects of each d...

Crude drugs whose active constituents are localized in leaves The pharmacognostical study includes: 1. Botanical studies: to be able to identify the drug in its entire form and identify its powder. 2. Overview on the main active constituents, uses and side effects of each drug.  Plant parts: Shoot system which consist of stem carrying 1. Leaves: responsible for photosynthesis and hence food formation. 2. Flowers: responsible for reproduction. After fertilization it transforms in fruit which contain seeds. 3. Apical bud: responsible for elongation of stem 4. Axillary bud: responsible for giving lateral branches or flowers Root system responsible for absorbing water and nutrients which are essential for living and photosynthesis. 1. Primary root: the main one 2. Lateral root: branches from tap root. Translocation of water, nutrients between different plant parts takes place through vascular bundle: which consist mainly of: Xylem: responsible for water and mineral transport (raw material) Phloem: responsible for transport of food.  Leaves are lateral outgrowths on the stem. They have no nodes or internodes. But they have lateral branches arising in their axils. Consists of three parts: 1) Leaf lamina (The green wide part) 2) Leaf petiole (connects leaf to stem) 3) Leaf base (place of attachment to the stem) Leaf apex Leaf margin axillary Bud Vennation Midrib Leaf lamina Leaf petiole Leaf base  Functions of the leaf: 1. Photosynthesis 2. Formation of food materials. 3. Gas exchange between outer atmosphere and inner tissues (by stomata).  Types of leaves 1-Foliage leaves 2-Floral leaves 3-modified leaves  Types of leaves 4-Cotyledons 5-Prophylls 6-Bracts 7-Scaly leaves  Macromorphology of leaves 1- Leaf Insertion Radical Cauline Leaves are arranged Leaves are arranged on a discoid stem on elongated stem crowded on top of root eg: Carrot.  2- Leaf Phyllotaxis Arrangement of leaves on the elongated stem Alternate or spiral Opposite One leaf on each node Two leaves on the same node opposite to each other  Opposite decussate Whorled or verticillate Two leaves opposite Three or more leaves each pair is perpendicular on each node to the pair above and below  3- Leaf base or phyllopodium a. Stipules b. Sheath a. Stipules Lateral projection at the leaf base For protection of the axillary bud May be hairy, leafy or spiny Present Absent Stipulate Exstipulate  Shapes of stipules: -Leafy -Spiny -Tendrils  The leaf base or phyllopodium: stipulate or ex-stipulate. Some leaves have sheath (surrounds the stem).  4- Leaf petiole a. Occurrence b. Characters c. Pulvinous a. Occurrence Petiolate Sessile  5- Lamina or leaf blade It is usually flattened, having a green color. The lamina may consist of a continuous, undivided surface and the leaf is described as “Simple” or may be cut down into a no. of lobes, connected together and is said to be “Lobed or Divided’’, or it may be completely segmented into a number of separate leaflets or pinnae and thus called ‘‘Compound’’. Lobed Compound 1- Simple leaf: General outline or shape: A- Lamina having the same width: 1-Filiform 2-Acicular 3-Tubular 4-Linear 5-Oblong B- Lamina has the widest portion near the base: 1-Lanceolate 2-Ovate 3-Ensiform 4-Haustate 5-Cordate 6-Sagitate 7-Reniform C- Lamina has the widest portion near the apex: Lyrate D-Lamina is symmetric or rounded: Oval Elleptical Peltate Orbicular 2- Lobed leaf: The lobed leaf is considered as a simple leaf having the margin variously incised Pinnately-lobed Palmately-lobed A-If the incision is not more than halfway to the midrib or to the petiole, the leaf is described as: Palmatifid Pinnatifid  B-If the incision is more than halfway to the midrib or to the petiole, the leaf is described as: Palmatipartite Pinnatipartite C-If the incision is deeper reaching almost the midrib or to the top of the petiole, the leaf is described as: Pinnatisect Palmatisect  b. Incision Lobed Pinnate Palmate One main midrib several veins arising from the top of the petiole Pinnatifid Pinnatipartite Pinnatisect Palmatifid Palmatisect Palmatipartite  3- Compound leaf: The compound leaf consists of 2 or more leaflets, either coming out from the top of the petioles or arranged on a central axis called rachis which is continuous with the petiole and corresponds to the midrib of the simple leaf (Pinnate). ❑ As you see the main differences between compound leaf and the branch is the presence and absence of buds ❑ Compound leaves end with 1-2 leaflets + leaflets have no axillary buds. ❑ Branches have terminal and axillary buds Mirror image Types of compound leaves: A-Binate: with 2 leaflets. B-Ternate: 2 lateral and 1 terminal Petiole C-Palmate or digitate with 5 or more leaflets radiating out from the top of the petiole: D-Pinnate: with several leaflets arranged on the rachis: Rachis Petiole Bipinnate 6- Size of the leaf: Lenghth 7- Apex of the leaf: 1. Acute: < 90 2. Acuminate: < 45 3. Emarginate 4. Mucronate: Stiff point 5. Obtuse: Broad Apex Acute acuminate obtuse emarginate apiculus truncate mucronate  8- Margin Serrate Crenate Entire Dentate Ciliate  9- Base of the lamina 1.Symmetric: When equal on both sides. 2.Asymmetric: Unequal on both sides. 3.Decurrent: When extends down and adnate to the stem.  9- Base Symmetric Asymmetric Decurrent 10- Leaf venation The lines that appear on the surface of a leaf and look like blood vessels are called veins. The three main types are: A-Pinnate Pinnate Reticulate Pinnate Reticulate & anastomosing  B-Palmate Reticulate palmate C-Parallel  11- Surface of the leaf 1.The upper surface is darker in color. 2.The midrib is more prominent on the lower. 3.The leaf may be: smooth, rugose (wrinkled), punctate (dotted from oil glands), scabrous (rough), glabrous (free from hairs), pubescent, succulent (thick and fleshy).  12- Texture of the leaf 1.Membranous: very thin and pliable. 2.Papery: thin like paper. 3.Coriaceous: thick and leathery. 4.Succulent: thick and fleshy. Micromorphology of leaves (anatomy) To be able to differentiate between different plant powder, one should know basic anatomy concepts and basic anatomy of plant cells  Plant cell wall Middle lamella: pectin layer which cement the cell walls of two adjoining cells Primary cell wall: cellulose only Thin walled cell Plasma membrane cytoplasm Nucleus Vacuole or lumen Secondary cell wall: Thick walled cell cellulose or hemicellulose or lignin Pit: no secondary cell wall, exchange of fluids Plasmodesma: channels traverse the cell wall which allow transport and communication.  Composition of plant organs Any plant organ contain three types of tissue: 1. Epidermis: The first layer face the outer environment (protection) 2. Vascular tissue: in or near the center (transport and support) 3. Ground tissue: cells lie between the aformentioned layers (versatile in function) 1 Cells occupying the ground tissue could be 2 one of the following: 3 Cells of the ground tissue Parenchyma Collenchyma Sclerenchyma  Ground cells: Parenchyma Thin-walled cells (cellulose) with large intercellular spaces Function: 1) When contain chlorophyll ----- (Photosynthesis) ). In this case, it is called (Chlorenchyma) 2) when contain starch --- (Storage) 3) When enclosing air spaces (gas exhange). In this case, it is called (Aerenchyma) Starch granules Aerenchyma Chlorenchyma  Ground cells: Collenchyma -Similar in shape to parenchyma, but its cell wall is thick cellulosic. - according to location of deposition of cellulose, it is divided into: angular, lamellar, lacunar. - Main function is support, therefore present at the corners of the stem or following the epidermal cells - If contain chloroplast, then it can perform photosynthesis.  Ground cells: Sclerenchyma Dead cells which have thick, lignified cell walls.- Functions only for support.- according to the shape:- long cells with tapering ends which run - longitudinally in plant tissues called fibers Fibers in T.S. polygonal compact cells (sclereids)- Fibers in side-view Sclereids appear the same in both T.S. and side view Sclerenchyma also makes up the hard outer covering of seeds and nuts.  GROUND CELLS CHARACTRS PARENCHYMA COLLENCHYMA SCLERENCHYMA DEFINITION SIMPLE, LIVING, SIMPLE,LIVING,, SIMPLE,DEAD, STORAGE TISSUE MECHANICAL MECHANICAL TISSUE TISSUE ARRANGMENT LOOSELY Either loosely Compactly OF CELLS ARRANGED WITH arranged or arranged without INTERCELLULAR compactly intercellular SPACES arranged spaces Cell wall Thin, has only Thick has Thick ,made up of primary wall primary, a primary wall (cellulose) wall(cellulose), (cellulose) secondary wall &secondary wall (cellulose) (lignin) Tests Cellulose in collenchyma & Lignin + phloro- Parenchyma + chlorozinc iodide → glucin + conc Hcl Blue color → red color 46 Characters parenchyma collenchyma sclerenchyma functions Storage, Mechanical Mechanical respiration, support& support & photosynthesis, sometimes protection absorption photosynthesis (seeds,fruits) & storage occurrence In all regions of In shoot system In all regions of plants, forms only under plants,in fruit ground tissue epidermis, large walls &seed &epidermis, veins of leaves coat,stem,leaf xylem, phloem veins types 47  Plant cells are either: Thin walled Thick walled Have 1ry cell wall of cellulose Have only 1ry cell wall of cellulose & secondary cell wall of either Parenchyma Cellulose Lignin Collenchyma Sclerenchyma According to shape of cells Elongated with tapering ends Isodiametric Fibers Sclereids  Vascular tissue 1) xylem: for transport of water and minerals. 2) Phloem: for transport of food. 3) Cambium: tissue which actively divide and differentiate to give new xylem and new phloem.  Vascular tissue: Xylem -Consist of xylem vessels, tracheids and xylem fibers. - Vessels: continuous cylinder of elongated cells whose end walls are loosened. The walls are thick and lignified. The form of lignification is varying. - Tracheids: elongated cells with tapering ends and have thick lignified and pitted walls. - fibers: dead elongated cells with thick lignified walls. Xylem vessels and fibers in T.S. Lignification of xylem vessels (side view)  Vascular tissue: Phloem -Consist of sieve tube, companion cells and ± phloem fibers. - Sieve tube is a long cylinder of elongated thin-walled cells whose end walls are perforated, so called (sieve plate). - Companion cell is a living cell which controls the activity of the sieve tube. - No lignification (c.f. Xylem vessels and tracheids) Phloem in T.S. Phloem in side view Phloem elements Xylem elements Sieve tubes Companion Conduction Tracheids cells Xylem Phloem vessels fibers Xylem fibers Support  The Vasucular tissues Known as meristele. Kinds of vascular bundles: I. Collateral: The phloem present either above or below the xylem, it may be: 1. Open: Has cambium and not surrounded by bundle sheath, xylem found in rows (Dicoty.) Phloem cambium xylem 2. Closed: It has no cambium and surrounded by bundle sheath, V.B. are scattered (monocotyledon). II. Bi-collateral: has the phloem above and below the xylem. Phloem xylem Phloem III. Concentric a. Amphiphloic: With xylem at the center and phloem to the outside b. Amphixylic: with phloem at the center and xylem to the outside. Phloem xylem  The epidermis - One row of polygonal isodiametric or elongated cells, which in T.S. appear as elongated quadrangular cells. -The anticlinal walls (walls of cells) could be straight or wavy. - The cells are covered by cuticle which is composed of a waxy material called cutin. It prevents loss of water. Wavy anticlinal walls Components of epidermis 1) Epidermal cells 2) Stomata (transpiartion) 3) ±Hairs  Stomata -Epidermal structure specialized for exchange of gases. Singular: Stoma Osteole Subsidiary cell  Types of Stomata According to shape of guard cells Dumbbell shaped stomata Bean shaped stomata Graminaceous type: Maize, grass Dicotyledonous type