Plant Anatomy Lecture 2 Fall 2024-2025 PDF

Phrmcognosy I (PG 101 and CPG 101) Fall 2024-2025 Plant Anatomy Lecture 2 By Professor Dr Amani M. Marzouk PLANT TISSUES In plants with well defined tissues, the production of new cells is performed by certain growing regions call...

Phrmcognosy I (PG 101 and CPG 101) Fall 2024-2025 Plant Anatomy Lecture 2 By Professor Dr Amani M. Marzouk PLANT TISSUES In plants with well defined tissues, the production of new cells is performed by certain growing regions called meristems. Tissues are generally divided into: 1- Meristematic (has the ability to divide and giving rise to new cells). 2- Permanent tissues.  Types of Tissues Meristematic Permanent Tissues Tissues Dermal Vascular Apical Intercalary Lateral meristems meristems meristems Ground Secretory vascular cork interfascicular cambium cambium cambium Classification of meristems 1)Apical meristem: Located at the apices (tips ) of main and lateral branches of stems and roots to elongate them. 2)INTERCALARY: Lies at the internodes of monocot plants  3)Lateral meristem: Arranged parallel to the sides of the organs such as the vascular, cork and interfascicular cambia. a- vascular cambium: located between the xylem  phloem. b- cork cambium (phellogen): It divides tangentially producing cork cells to the outside and phelloderm to the (a) inside. (b) c- interfascicular cambium: originates between vascular bundles of the stem. (c)  THE PRIMARY PERMANENT TISSUES OF PLANT Permanent tissues : Those which lost their power of division. They may be classified according to their function, structure and position in the plant body into: A- The dermal tissues B- The ground tissues C- The vascular tissues D- The secretory tissues  A) THE DERMAL OR PROTECTIVE TISSUE This is the tissue forming the outer protective covering of the plant (the epidermis) like skin in animals. The epidermis (usually one layer of cells) covers the entire stem, leaf and root of the young plant. The cells are living have thick primary walls (cellulosic) and are covered on their outer surface by a special cuticle with an outer waxy layer that prevents water loss (except in roots). Why? Some of of the epidermal cells also modify to form Stomata and Hairs of various kinds (dermal appendagse).  There are no intercellular spaces between the epidermal cells. They form a continuous layer except in certain regions , especially on leaves and green stems, where stomatal pores are found. They are isodiametric cells in dicot leaves Sectional view of and elongated in monocot. Leaves and Epidermal cells stems of both types (in surface view). Surface view of epidermal cells  Different shapes of epidermal cells Straigt anticlinal walls and smooth cuticle Wavy anticlinal walls Striated cuticle Stomata Are openings in the epidermis mainly on the lower surface of the leaf. They regulate gas exchange in the plants Stomata (pl.) (stoma singular) consists of openings (osteole) surrounded by: 1- two guard cells which are: Kidney-shaped in dicots Dumbel-shaped in monocots 2- Subsidiary cells (2 or more Cells) Dumbel shaped stomata  Dicot Stomata Paracytic Diacytic Anisocytic Anomocytic Two Two 3-5 cells 3-5 equal subsidiary subsidiary One is epidermal cells with cells with distinctly cells their axis their axis smaller parallel to perpendicular the osteole to the osteole Rubiaceous Caryophyllaceous Cruciferous Ranunculaceous type st. type st. type st. type st.  Types of Dicot. stomata Anisocytic Anomocytic Diacytic Paracytic Structure of monocot stoamata (Graminaceous- type stomata)  EPIDERMAL MODIFICATIONS AND APPENDAGES They are commonly known as hairs or trichomes. according to their function they may be classified into glandular and non-glandular trichomes or hairs. Function of hairs (trichomes): Nonglandular hairs function for protection. Glandular hairs function for secretion. Unicellular tr Multicellular Uniseriate Unbranched Multicellular Biseriate Stellate Non glandular Branched Candelabra Unicellular stalk Unicellular head Trichomes Capitate tr Unicellular stalk Multicellular head Multicellular stalk Glandular Labiaceous tr Unicellular head Branched gl tr Clavate tr  Trichomes Non- Glandular glandular UnicellularMulticellular Unbranched Branched Uniserriate simpleٍ Biserriate Stellate Multiserriate Candelabra Nonglandular trichomes 1-Unicellular trichome 2- Multicellular uniseriate non gl. Tr. 3- Multicellular Biseriate non gl. Tr. 4- Candelabra tr. Stellate tr.  Glandular Trichomes Unicellular stalk Multicellular stalk Uniseriate stalk, Unicellular head unicellular head Multiseriate, Multicellular stalk, Bicellular head multicellular head Branched stalk Multicellular head with unicellular head 1- Capitate tr. Unicellular head and unicellular stalk Bicapitate tr. Bicellular head and unicellular stalk 2- Multicellular uniseriate stalk and unicellular head gl. Tr. 3- Branched gl. Tr. Multicellular branched stalk and unicellular heads 4- Clavate gl. Tr. club-shaped; thicker at the apex than at the base. It has a multicellular multiseriate head and a unicellular stalk. 5- Labiaceous gl. Tr. The head consists of eight radiating cells surrounded by raised cuticle and a unicellular stalk. Side view Surface view 6- Compositae gl. Tr. It consists of multicellular biseriate head and a multicellular biseriate stalk. Surface view Side views 2-The ground or fundamental tissues They form the bulk of the plant body 1- parenchyma 2- collenchyma 3- sclerenchyma a) Fibres b) sclereids Fibres in T.S Fibres in L.S T.S in dicot stem showing different types of tissues Epidermis (Derml tissue) Collenchyma (Ground tissue) Schlerenchyma (Ground tissue) Vascular tissue Ph. And xy. Parenchyma (Ground tissue) 1- parenchyma:They are living cells, Having thin cellulosic walls.  Parenchyma cells perform several functions as storage of water and food such as starch, fat and protein.  If chloroplasts are present, these cells are capable of carrying out photosynthesis and usually known as chlorenchyma.  They may store air in wide intercellular spaces and called aerenchyma as in aquatic plants.Aquatic plant leaves contain Aerenchyma which are modified parenchyma consisting of chains of small cells enclosing very wide intercellular spaces. cells cells Air Air space space  XXXX 2- collenchyma They are living cells, more elongated and narrower than parenchyma cells with thick cellulosic non-lignified walls. They act as a supporting tissue in young growing organs as dicot lacunar stems and leaves. 3-sclerenchyma They are non-living cells with thick lignified secondary walls. They function for support They are classified into: a) Fibres b) sclereids a) Fibres Shape: long, narrow, spindle - shaped, with secondary lignified pitted walls and narrow lumen. Location: Xylary (occur in xylem tissue) and extra-xylary (in other tisues than xylem). b) Sclereids sclereids: are a type of reduced sclerenchyma cells which have various shapes, mostly isodiametric. 3) THE VASCULAR OR CONDUCTING TISSUES They comprise xylem, the principle water conducting tissue and phloem, the food conducting tissue (together they form the vascular bundles). a- Xylem: Xylem is a complex tissue that is consisting of several types of cells. The characteristic components are the tracheary and atracheary elements. The tracheary elements (tracheids and vessels) have the function of conduction with that of support. Atracheary elements: Xylem fibres and parenchyma. They have no role in conduction. Fibres are specialized supporting elements, while xylem parenchyma perform vital activities. Tracheids They are conducting elements and serve also for support. Each tracheid is a single, elongated cell with bluntly tapering ends. Pitted (bordered type pits) walls Non-perforated end walls (c.f. vessels). Tracheids showing bordered pits Xylem (Wood) vessels: Vessels are narrow or wide water conducting tubes, formed from a number of cells, by a partial or complete disintegration of their end walls. (perforated end walls) c.f. tracheids Types of xylem vessels: They are classified according to the shapes of deposition of the secondary wall material on the primary walls into: 1- Annular:When the thickenings are in the form separate of rings at intervals. 2- Spiral: when the wall show a spiral line of thickening. 3- Reticulate When the thickening of the walls takes the form of a network. 4- Pitted When the whole wall becomes thickened except of numerous small areas or pits which are usually bordered. b- Phloem Phloem is also a complex tissue, composed of several different kinds of cells. Phloem is composed of : - Sieve tubes - Companion cells - Phloem parenchyma Phloem - Phloem fibres plasmodesmata Phloem parenchyma Types of V.B. 1- Collateral: phloem and xylem are on the same radius, with phloem to the outside and xylem to the inside. a- Open : In most dicot. stems It has a vascular cambium between xylem and phloem b- Closed: In monocot. plants The vascular bundles have no cambium. 2- Bicollateral : xylem occurs between two patches of phloem. 3- Concentric: a- Vasocentric: xylem concentrated in the center and surrounded by phloem. b- Amphivasal: phloem concentrated in the center and surrounded by xylem. 4- Radial: xylem and phloem patches are on different radii (as in root).  4-The secretory tissues Glandular hairs Cells glands hydathodes nectaries ducts Glands are classified into: Secretory: retain (keep) their secretions inside the secreting cells. Excretory: secretions are exuded outside the secreting cells. A- Internal glands: They retain their secretions in central cavities in the plant tissue. These cavities originate in two ways: 1- by gradual separation of cells through the dissolution of the middle lamellae. This type is called schizogenous These constitute the epithelium which discharge their secretion into the central cavity. 2- through the dissolution (lysis) of entire cells, leaving a space in which the secretion accumulates. It is called (lysigenous) and the cavities usually contain the remains of cells. 3- Schizolygenous oil glands: Schizogeny (cell separation) Is followed by cell lysis Schizogenous Lysigenous Schizolysigenous oil glands 4- Ducts Voltile oils, Resins, latex and gums are often secreted and conducted within the plant body in ducts.  XXXXXXXXXXXXXX ‫ملغية‬ B- External glands: Nectaries These are simply modified patches of the epidermis found in most flowers. The epidermis of these gland areas has no cuticle. They secrete sugary substance, known as nectar, it serves to attract insects.