Plant Anatomy PDF

Introduction to Plant Anatomy Dr. Gehad Abd-Allah Ragab Dr. Gehad  Plant Anatomy The branch of science which studies the internal structure of the plant body. Importance of anatomical studies: 1. helps in understanding of how the plant body function...

Introduction to Plant Anatomy Dr. Gehad Abd-Allah Ragab Dr. Gehad  Plant Anatomy The branch of science which studies the internal structure of the plant body. Importance of anatomical studies: 1. helps in understanding of how the plant body functions. 2. help us in solving taxonomic problems. 3. Essential for pharmacognosy Dr. Gehad  Plant Body organization The plant body is made up of cells. Cells represent the smallest structural and functional units of life. The cells are organized into tissues. Tissues form different organs. Dr. Gehad  The plant cell is formed from the protoplasm surrounded by the cell wall which protects and supports it. Protoplasm Cell wall Shape Protection Support Strength Dr. Gehad  Cell wall structure Middle lamella The middle lamella is the first layer of the cell wall, formed at the end of the cell division and deposited between the newborn cells. It composed of pectin to adhere Middle lamella Dr. Gehad cells to each others forming tissues  Primary cell wall Thin, elastic, expand during cell growth Composed of cellulose fibers (polysaccharides) imbedded in matrix of: Pectin, hemicellulose, and protein Secondary cell wall rigid non- elastic formed after cell maturation. Besides cellulose, hardening agents are added including Dr. Gehad lignin, cutin, or subrin. Dr. Gehad The cell wall structure 1- The middle lamella is the first layer of the cell wall, formed at the end of the cell division and deposited between the newborn cells. It composed of Pectin to make cells adhere to each others forming tissues 2- The primary cell wall deposited on both sides of the middle lamella elastic and can be stretched, composed of cellulose fibers and hemi-cellulose layers. 3- The secondary cell wall rigid non- elastic layers developed by the deposition on the inside surface of primary wall after cell full growth. It composed of celluloses, hemicellulose and other hardening agents such as lignin, cutin, or subrin to provide strength. Dr. Gehad Pits: are definite pores left without deposition of cell wall components, commonly formed in pairs on 2 adjacent cells. Plasmodesmata is cytoplasmic strands pass through the pits to connect the neighboring protoblasms. transport materials and stimuli between cells Dr. Gehad  Pits Dr. Gehad  The Protoplasm and its components Protoplasm is composed of plasma membrane containing cytoplasm and different organelles (protoplasmic -living contents). 1- Protoplasmic -living contents Nucleus -It is surrounded by nuclear membrane (double-layered), - contains dense bodies (nucleoli) and chromatin diffused in the nuclear sap. - During cell division the chromatin becomes organized into chromosomes. Endoplasmic reticulum is a continuous membrane bound system of flattened sacs and tubules, sometimes coated with ribosomal particles. Mitochondria surrounded by double membranes for respiration as energy factory. Dr. Gehad  The plastids surrounded by double membranes and classified depending on their function: ❖Chloroplast is plastid contains chlorophyll the photosynthetic pigment and specialized for photosynthesis in all green plant tissues. ❖Chromoplast is a plastid contains colorful pigments and gives colors to plant organs (e.g flowers, fruits…). ❖Leucoplast is a non-pigmented (Lacking photosynthetic pigments), and located in non-photosynthetic tissues of plants, such as roots, bulbs and seeds. They are specialized for nutrients storage (starch). Vacuoles are cavities in the cytoplasm, surrounded by vacuole membrane known as tonoplast. It regulate the turgidity and osmosis of the cell. Dr. Gehad The Protoplasm and its components 2- Non-protoplasmic (non-living) contents Storage or waste compounds such as starch grains, protein, oil bodies and mineral matters in crystals-form. Starch grains formed in plastids called amyloplasts. Starch grains show layering around a point, the hilum. Concentric grains with hilum at the center branched or unbranched. Excentric grains with the hilum on one side and may be simple or compound. Dr. Gehad  Organic Starch grains Concentric Ex-centric Dr. Gehad Calcium oxalate crystals formed mainly within vacuoles of actively growing cells: Druses are aggregated crystalline structures precipitated around a nucleation point as stare-shaped. Raphides are bundles of calcium oxalate needle-like crystals that are borne in the same cell. Dr. Gehad  Plant tissues A tissue is a group of cells having a common origin and usually performing a common function. Meristematic Permanent Tissues are classified into two main groups, namely, meristematic and permanent tissues based on whether the cells being formed are capable of dividing or not. Growth activity in plants is largely restricted to specialized regions of active cell division called meristems Dr. Gehad  Plant Body organization Each plant seed has an embryo. On germination, the embryo gives an embryonic shoot (plumule), embryonic root (radicle) and one or two seed leaves (cotyledons). After growth activity, active cell division is largely restricted to specialized regions of called meristems. Dr. Gehad  Meristematic tissues Group of undifferentiated cells have the same origin and divide continuously. Properties of meristematic cells 1. The shape of the cells may be oval, rounded or polygonal. 2. Thin walls due to the absence of secondary wall 3. Large nuclei 4. Dense cytoplasm. 5. Absence or few small vacuoles 6. Lack of intercellular spaces Dr. Gehad Dr. Gehad  Types of meristems according to position 1- Apical meristems: located at the apex of stems and roots responsible for primary growth and increase length of the plant. 2- Intercalary meristems: Part of the apical meristems separated during development, -located between permanent tissues away from the apex. -It increase the plant organ length and finally turned into permanent tissue. Ex: at the nodes, and leaf bases 3- Lateral meristems: found parallel to the long axis of the plant organs, and are responsible for increasing the plant thickness. Dr. Gehad Dr. Gehad Dr. Gehad  Permanent tissues They are group of cells have the same origin and function but lost the ability to divide and differentiated to apply a specific function. Permanent tissues having all cells similar in structure and function are called simple tissues. Permanent tissues having many different types of cells are called complex tissues. simple compound Dr. Gehad  Simple tissues Sclerenchyma Parenchyma Chollenchyma Dr. Gehad  Simple tissues tissues consist of single type of cells such as parenchyma, collenchyma and sclerenchyma 1- Parenchyma Characters➔ thin walled (primary wall) living cells, have cytoplasm, nucleus, chloroplasts, and characterized by intercellular spaces between the cells. Functions ➔carry out most of metabolic functions in plant body including: food storage, gas-exchange via their intercellular spaces, photosynthesis due to containing many chloroplasts and called “chlorenchyma”, secretion, and may retain the dividing ability Types ➔ according to the cell shape are: spherical, angular, elongated, lobed….etc. Dr. Gehad Types Dr. Gehad spherical Chlorenchyma Dr. Gehad Chlorenchyma Elongated and lobed 2-Chollenchyma Characters➔ living elongated cells, with irregular thickened cell walls (primary wall, thickened with cellulose) and tightly packed (without intercellular spaces). distributed below the epidermis in most of the dicot plants. Functions ➔mechanical support with semi-elasticity to give the strength to the growing parts of the plant. Types ➔ according to the cell wall thickening into: a-Angular: thickening deposited only on the angles (intercellular spaces) between cells. b- Lamellar: thickening deposited on the tangential walls c- Cartilegenous: thickening deposited the cell walls and the intercellular spaces. Dr. Gehad Types Dr. Gehad  Collenchyma Angular Parenchyma Dr. Gehad Angular  Collenchyma Angular Parenchyma Dr. Gehad Angular 3- Sclerenchyma Characters➔ Non-living cells with thick and lignified cell walls (secondary ) with no intercellular spaces. Functions ➔mechanical support and protection. Types ➔ They are divided into : a) Fibers: long narrow and elongated cells with tapered ends. If they found with the xylem they are called xylary fibers and if they are found in other tissues they are called extraxylary fibers b) Sclerides: are shorter than fibers, have more thicker walls, and have different shapes, they may be isodiametric, bone shaped, rod shaped or star shaped. Ex. Astrosclerids and Osteosclerids Dr. Gehad Sclerenchyma Fibers a) Fibers: long narrow and elongated cells with tapered ends. - If they found with the xylem they are called xylary fibers and - If they are found in other tissues they are called extraxylary fibers extraxylary Dr. Gehad Extra-xylary fibers Extra-xylary fibers Xylary fibers Xylary fibers Dr. Gehad b) Sclerides: - Short cells (shorter than fibers), have more thicker walls, and have different shapes, - they may be isodiametric, bone shaped, rod shaped or star shaped. Osteosclerids Ex. Astrosclerids and Osteosclerids Astrosclerids Dr. Gehad Complex tissues The complex tissues are made of more than one type of cells and these work together as a unit. E.x. Xylem and phloem constitute the continuous vascular tissue. Xylem functions as a conducting tissue for water and minerals from roots to the stem and leaves. Phloem transports food materials, usually from leaves to other parts of the plant Dr. Gehad Dr. Gehad The xylem: As a complex tissue, it consist of four elements; 1- Vessels, Conducting elements 2- Tracheids, Conducting elements 3- Xylem Fibers Non-Conducting elements 4- Xylem parenchyma. Non-Conducting elements The conducting elements (tracheary) including vessels and tracheids have very rigid, lignified and pitted cell wall, and better preserved in fossils. Dr. Gehad  1- Vessels series of elongated elements joined end to end forming tube-like structure have thick lignified, pitted cell walls have wide diameter, and round perforated ends Dr. Gehad  2- Tracheids main conducting element in gymnosperms consist of a series of elongated cells as vessels joined end to end forming tube-like structure, but absent in dicots. have thick lignified pitted cell walls, angular in transverse section. have non perforated tapering ends. Dr. Gehad 1-The vessels: main conducting element in angiosperms. - consist of a series of elongated elements joined end to end forming tube-like structure. - with thick lignified, pitted cell walls - have wide diameter, and round perforated ends compared to tracheids. - The first formed primary xylem elements are called protoxylem (proto, first), and the later formed primary xylem is called metaxylem (meta, after). 2- Tracheids: main conducting element in gymnosperms consist of a series of elongated cells as vessels joined end to end forming tube-like structure, but absent in dicots. - have non perforated tapering ends. - with thick lignified , pitted cell walls, angular in transverse section. Dr. Gehad  The first formed primary xylem elements are called protoxylem (proto, first), and the later formed primary xylem is called metaxylem (meta, after). Dr. Gehad Cell wall lignifications of xylem tracheary elements Depending on the mode of thickening, there are annular, spiral, scalariform, reticulate or pitted lignification 3- Xylem parenchyma: living parenchyma cells to store food and secondary metabolites. 4-Xylem fibers: sclerenchyma fibers for support and strength, with very thick walls. Dr. Gehad  Tissues Compound tissues Compound tissues 1- Xylem in Dicot 1- Xylem in Monocot 2- Phloem Phloem Xylem in monocot The phloem transports food materials, usually from leaves to other parts of the plant. Among those substances are sugars, amino acids, micronutrients, lipids (in form of fatty acids), hormones and numerous proteins Phloem in angiosperms is composed of: 1- Seive tubes 2- Campanion cells 3- Phloem fibers 4- Phloem parenchyma Dr. Gehad 1- Sieve tubes: are the conducting elements of phloem tissue, and have long, tube-like structure. composed of group of thin-walled cells arranged longitudinally. Their transverse walls are perforated in a sieve-like manner to form the sieve plates. Sieve tube walls are made up of cellulose (primary wall) like parenchyma. At maturation their nuclei degenerate and the cytoplasm becomes confined to a thin layer around the wall (peripheral). The functions of sieve tubes are controlled by the nucleus of companion cells. Dr. Gehad 2- The companion cells specialized living cells with dense cytoplasm and large nuclei, and associated with sieve tube elements. regulate the passage and movement of substances inside the sieve tubes. It is lying parallel to sieve tubes and originate from the same meristematic cell by longitudinal division. 3- Phloem parenchyma: living parenchyma cells to store food. 4-Phloem fibers: sclerenchyma fibers Longitudinal section for support with thick walls. Dr. Gehad Vessel Seive tube Dr. Gehad Dr. Gehad Phloem cross section Dr. Gehad Longitudinal section  Tissue systems Large units of tissues have common features such as the same location and continuity or function in the plant body. There are three types of tissue systems. 1- The epidermal tissue system 2- The ground fundamental tissue system 3- The vascular or conducting tissue system. Dr. Gehad  Epidermal Tissue System Outer-most covering layer of the whole plant body and comprises : – epidermal cells (living cells), – Stomata(pores between the epidermal cells controlled by guard cells), – epidermal appendages – the trichomes and hairs. Epidermis is usually made up of compactly and tightly- packed single layered. The outside walls of the epidermis is often covered with a waxy thick layer called the cuticle which prevents the loss of water. Cuticle is absent in roots. Dr. Gehad Functions of the dermal tissue system specialized for protection of internal tissues against mechanical injury, pathogen infection and against cold or heat. Thick cuticle and wax layers reduce water loss, Stomata help in gaseous exchange between the internal tissues and the environment Unicellular root hairs help in water absorption. Dr. Gehad  Ground tissue system All tissues except epidermis and vascular bundles constitute the ground tissue. It consists of simple tissues such as parenchyma, collenchyma and sclerenchyma. usually differentiated into cortex, pericycle, pith in stems and roots. In leaves, consists of thin-walled chloroplast containing cells and is called mesophyll. Functions of the ground tissue: – The ground tissue is concerned mainly with mechanical support and food storage – Photosynthesis (food making) occurs mainly in the parenchyma cells of the ground tissues in the shoot parts Dr. Gehad  Vascular tissue system The vascular system distributed within the ground tissues consists of complex tissues, the phloem and the xylem. The xylem and phloem together constitute vascular bundles. The function is to conduct water and food while also give strength. closed collateral Radial open collateral Dr. Gehad Concentric The types of the vascular bundle depend on the arrangement of xylem and phloem relative to each other: 1. Collateral: xylem and phloem are found on the same radius. If cambium is found between xylem and phloem is called open collateral (found in dicot plants), If no cambium between the xylem and the phloem it is called closed collateral (found in monocot plants). 2. Radial: xylem and phloem are found on different radii. This type is common in roots. 3. Concentric : xylem and phloem lie on concentrically i.e. one surrounds the other completely. When xylem lies in the center and is completely surrounded by the phloem it is known as amphicribral. When phloem lies in the center and is surrounded by the xylem amphivasal. Dr. Gehad  Systems Dr. Gehad Dr. Gehad  Anatomy of young root Dicot Monocot Dr. Gehad I- Dicot root Dr. Gehad Dicot root →The internal tissue organization is as follows: 1-epidermis the outermost layer formed of compactly arranged cells and have thin walls. It extends outwards forming unicellular root hairs. They maximize the root’s water absorption as they increase its surface area. 2-The cortex consists of several layers of thin-walled parenchyma cells have intercellular spaces. - The cells of the cortex store food and conduct water from the epidermis to the inner tissues. 3-The endodermis is the innermost layer of the cortex which is: - a single layer of barrel-shaped cells without any intercellular spaces. - They have thickened walls with a deposition of water-impermeable (waxy) material suberin in the form of casparian strips. - The cells of endodermis lying opposite to the protoxylem have a thin cell wall and enables passage of water and minerals from cortex into xylem, thus called passage cells. The endodermis serves as a selective barrier between the ground tissue (cortex) and the stele Dr. Gehad 3- The stele➔ All tissues on the innerside of the endodermis such as pericycle, vascular bundles and pith constitute the stele. a-Pericycle lies next to endodermis and made of thin-walled parenchyoma cells. It give rise to lateral roots. b-The vascular bundle is radial (separate bundles (arms) of xylem and phloem arranged alternatively). They are usually four xylem and phloem patches. c- The pith is small or absent, consist of parenchyma cells which share in food storage. Dr. Gehad Dr. Gehad Dr. Gehad  Monocot root The anatomy of the monocot root is similar to the dicot root except for: 1- As compared to the dicot root cortex in monocot is less wide than the dicot roots. 2- presence of exodermis below the epidermis (in older stems, outer few layers of the cortex become suberized). 3- In the moncot root, there are usually more than six xylem arms (polyarch). Dicot V.B has fewer xylem arms. 4- Pith is large and well developed. 5- The tissue that separates xylem and phloem may be either parenchyma or sclerenchyma. In dicots, it is parenchyma. Dr. Gehad Dr. Gehad Dr. Gehad Dr. Gehad Dr. Gehad Anatomy of young plant organs Dr. Gehad  Anatomy of young stem Monocot Dicot Plant stems have many functions: 1. The stems provide a support for plant body 2. Elevation of leaves, flowers and fruits 3. They help the transport of fluids between the roots and the shoots in the xylem and phloem Dr. Gehad  Anatomy of young stem Monocot Dicot Dr. Gehad Diagram of young dicot stem Dr. Gehad  Dicot stem The transverse section of a young dicot stem shows: 1- The epidermis - is the outermost protective layer of the stem, - consists of a single layer of barrel shaped parenchyma cells. - It covered with a thin layer of cuticle and have stomata controlled by guard cells - may contain several trichomes or epidermal hairs 2- Hypodermis consists of a few layers of collenchyma below the epidermis, which provide mechanical strength and flexibility to the young stem. it participates in photosynthesis due to presence of chloroplasts. The ground tissue cells arranged in multiple layers between epidermis and vascular system constituting three sub-zones: Dr. Gehad 3- The cortex -several layers below hypodermis consist of spherical parenchyma layers to store food. -In green stems, outer few layers of cortex may contain chloroplasts and contribute in photosynthesis - innermost layer of the cortex is rich in starch grains and referred to as the starch sheath and has wavy shape. 4- Pericycle is present on outer boundary of the vascular system and lies below the starch sheath. It consists of Few layers of sclerenchyma fibers (extra-xylary) Dr. Gehad 5- Vascular bundles -They are arranged in the form of a ring around the central pith and their type are open collateral - Each vascular bundle consists of phloem on the outside connected to the xylem with a strip of cambium in-between. - Protoxylem lie towards the centre and metaxylem lies outside 6- Pith lies at the centre of stem. It consists of parenchyma and helps in storage of food. 7- Medullary rays or pith rays strips of parenchyma; occurs between vascular bundles as rays and connect the pith with the cortex Dr. Gehad Dr. Gehad Monocot stem Dr. Gehad Monocot stem 1-The epidermis - is the outer most layer, consists of a single layer of barrel shaped cells covered with cuticle - Some stomata may present 2- hypodermis - lies below the epidermis consists of two or three layers of sclerenchyma fibers. - provides support and strength to the stem 3- ground tissue - consist of large number of parenchyma layers with scattered vascular bundles within. - It is not differentiated into cortex and pith that. Dr. Gehad 4-Vascular bundles They are scattered in the ground tissue Peripheral vascular bundles are smaller than the central ones Each vascular bundle is surrounded by a sheath of sclerenchyma fibers called bundle-sheath to provide protection and strength to the V.B Vascular bundles are closed collateral. Since there is no cambium Xylem It consists of 3 distinct vessels arranged in the form of (Y). Two larger vessels with tracheids in between them forming metaxylem. Protoxylem consists of a smaller vessel towards the centre. Xylem parenchyma and fibers are associated with protoxylem that have Xylem cavity Phloem lies in between the arms of xylem facing the epidermis and Phloem parenchyma Dr. Gehad is absent. Dr. Gehad  Anatomy of leaves monocot dicot leaves have many functions: 1- photosynthesis where the structure of eaves has specialized tissues to expose the photosynthetic organelles (the chloroplasts) to light. 2- Gas exchange is controlled by stomata, which open or close to regulate the exchange of gases with the atmosphere. 3- Many leaves are covered with trichomes which have a diverse range of structures and functions Dr. Gehad  Dicot 1- Epidermis: The upper and lower surface of leaf is bound by upper and lower epidermis. Upper epidermis: is a single layer of barrel shaped living cells that usually have chloroplasts. Cuticle forms a distinct outer surface on the epidermis to prevent gas loss or transpiration and protects internal cells against injury Lower epidermis: is similar to the upper epidermis, but have a large number of stomata on the lower surface. Each stoma contains a narrow pore surrounded by kidney shaped guard cells. Stomata contribute in exchange of gases and in transpiration. Dr. Gehad Dicot Dr. Gehad 2- Mesophyll is the ground tissue of the leaf and lies between the upper and lower epidermal layers. - It is a green parenchyma tissue and can be differentiated into: Palisade parenchyma occurs below the upper epidermis and contains closely elongated packed cells with small intercellular spaces. Spongy parenchyma is positioned between palisade and lower epidermis. The cells are irregular in shape (lobed) and have large intercellular spaces in between to allow free movement of air. 3- Vascular system (veins of the leaf) Vascular bundles are distributed between palisade and spongy parenchyma. Each V.B is open collateral in an inverted position. Xylem directed to the upper side of the leaf whereas phloem directed to the lower surface with cambium in-between. Bundle sheath, parenchyma cells surrounds each V.B for food storage. In the midrib region, several layers of collenchyma lie beneath the upper and lower epidermis for support and elasticity. Dr. Gehad Dr. Gehad Moncot Dr. Gehad  Monocot 1- Epidermis: there are upper and lower epidermal layers. Each epidermis is formed of a single layer of barrel shaped cells. A distinct layer of cuticle is visible on the outer surface. Stomata are present on both the upper and lower epidermis. Each stoma has a small pore and a pair of dumb bell shaped guard cells. Some of the cells of upper epidermis are thin walled and have large vacuoles. These cells are called motor cells and have a role to play in the rolling and unrolling of linear leaves. 2- Mesophyll The mesophyll cells contain chlorophyll and participate in photosynthesis. Consists of thin walled isodiametric cells with intercellular spaces. Unlike dicot leaves, mesophyll tissue in monocot leaves is not distinguished into palisade and spongy tissues. Dr. Gehad Dr. Gehad 3- Vascular system is made up of vascular bundles or veins. The vascular bundles are closed collateral. Xylem lies towards the upper surface and phloem towards the lower surface (with inverted position). Bundle sheath of sclerenchyma fibers surrounds each vascular bundle. In the midrib region, few layers of fibers lie beneath the upper and lower epidermis for support. Dr. Gehad Dr. Gehad