Botany Chapter 3 Tissues 2005 PDF

Dr.Mohamed Elshebly BOTANY CHAPTER 3 TISSUES Prepared by: ‫محمد‬.‫د‬ ‫الشبلي‬ 2005 1  Dr.Mohamed Elshebly Plant anatomy : its the study of internal structures of specifiec part or organ...

Dr.Mohamed Elshebly BOTANY CHAPTER 3 TISSUES Prepared by: ‫محمد‬.‫د‬ ‫الشبلي‬ 2005 1  Dr.Mohamed Elshebly Plant anatomy : its the study of internal structures of specifiec part or organs. Plant Morphology : is the study of the external structures or form of the plant organs such as leaves , stems , roots , flowers & fruits. Despite their apparent diversity, all seed plants have the same basic body : 1 -- The vegetative body is composed of three organs: leaf, stem, and root. 2 -- There are two categories of seed plants: gymnosperms &angiosperms. 3 -- New cells are produced by dividing tissues called meristems.  Three major tissue systems make up the plant body are found in all plant organs: Dermal tissue, Ground tissue, and Vascular tissue. Tissues of plants : plants are immobile & hence have been provided with tissues made up of dead cells , which provide structural strength. They have to endurate unfavorable enviroment like strong winds , storms , floods. Meristematic tissues Throughout the life of a plant, new cells are continuously being formed at sites called meristem. 2 Dr.Mohamed Elshebly 3  Dr.Mohamed Elshebly THE NATURE OF PLANT MERISTEMS :  Unlike animals , which are characterized by a generalized growth pattern , plant growth is limited to certain regions where the cells retains the capacity for continued cell division. Meristems are classified by their location in plants as 1 On the very ends of roots AMs (Root Apical Meristems) & stems (Shoot Apical Meristems). 2 Lateral LMs (in the vascular and cork cambia). 3 Intercalary. NOTE : (AMs give rise to the primary plant body & are responsible for the extension of the roots & shoot.) 4  Dr.Mohamed Elshebly - (LMs are known as secondary meristems because they are responsible for secondary growth, or increase in stem girth & thickness.) Meristems are centers of plant growth :  Only primary growth, resulting from the activity of the SAM & RAM, is found in some herbaceous dicots, most monocots, & lower vascular plants.  Tissues that are derived directly from the SAM & AM are called primary tissue.  Conifers & woody dicot shrubs & trees exhibit secondary growth.  The stems & roots of woody plants grow in diameter (girth) result from the acivity of the vascular cambium ( secondary tissue ).  The vascular cambium develops between the xylem & phloem & produce new xylem inside & new phloem outside.  Cork cambium is also a secondary tissue gives the periderm which replace the epiderms. 5  Dr.Mohamed Elshebly THE SHOOT APICAL MERISTEM ( SAM) :  SAM is strucurally more complex than root apical meristem.  SAM form the lateral organs such as leaves , branches & floral parts.  The outer most layer of SAM is called tunica & the innermost layers are corpus. In monocots : the tunica determine the charachtaristics of leaf edge. In dicots : layer two of the corpus determine the charachtaristics of the leaf edge.  SAM Up to 3 mm in size & has : A -- Central zone CZ ( Containing the stem cells ). B -- Peripheral zone PZ ( Which produce leaf primordia ). C – Rib zone RZ lie below the CZ & generates the central tissue of the stem. 6  Dr.Mohamed Elshebly THE ROOT APICAL MERISTEM RAM:  Only the root cap & the cell division regions actually move through the soil. After cells start to elongate & mature, no further extension takes place, & the root is stationary for the rest of its life. Zones of developing root : 1 -- The root cap : covers the tip of the root. As cells are lost among the soil particles, new ones are added from the meristem behind the cap.  The cap protects the cells under it from abrasion & assists the root in penetrating the soil Mucilage: consisting of polysaccharides containing hexose & pentose sugars & uronic acids , is secreted by root cells as root grow throgh the soil.  This mixure of gelatinous material , microorganisms & soil particles is termed mucigel.. NOTE : The mucigel 1 -- Lubricates the roots. 2 -- Contains materials that are inhibitory to roots of other species. 3 - Influences ion uptake. 4 - Attracts beneficial soil microorganisms. 5 - Glues soil particles to the roots thereby improving the soil-plant contact & facilitating water movement from the soil into the plant. 6 - Protects the root cells from drying out. 2 – ZONE OF THE CELL DIVISION : M An apical meristem lies under & behind the root cap & it produces the cells that give rise to the primary body of the plant. M Between the area of active division & the cap is an area where cells divide more slowly, the quiescent center. The apical meristem of the root organizes to form the three primary meristems: A -- Protoderm, which gives rise to the epidermis B -- Procambium, which produces xylem & phloem; and C -- Ground meristem, which produces the cortex. NOTE : Pith : present in most stems & produced from the ground meristem, is absent in most dicot roots, but is found in many monocot roots. 7  Dr.Mohamed Elshebly 3 -- Zone of cell elongation:- M The cells in this zone stretch & lengthen as small vacuoles within the cytoplasm coalesce & fill with water. M Cellular expansion in this zone is responsible for pushing the root cap & apical tip forward through the soil. 4 -- Zone of maturation:- M The elongating cells complete their differentiation in this zone. M It is easily recognized because of the numerous root hairs that extend into the soil as outgrowths of epidermal cells. 8  Dr.Mohamed Elshebly Intercalary meristem :  In angiosperms , Found only in monocots stem ( in partticular grass) at node & leaf blades.  capable of cell division & they allow for rapid growth & regowth.  Intercalary found at nodes of bamboo allow for rapid stem elongation , while those grass leaf blades allow damaged leaves to rapidly reggrow. Permanant plant tissue :  permenanr tissues : completely grown & lost their ability of division.  Meristematic tissue cells can divide & differentiate to form the permanant tissues. Types of permanent tissues : 1 – Simple : Also known as homogenous tissues , they are made up of a single cell type , usually with same origin , structure & function. 2 – complex : tissues are composed of more than on type of cells. 9  Dr.Mohamed Elshebly Simple tissue is divided into three types : 1 – Parenchyma : alive , polygonal cells with a big central vacuole & have intercellular spaces amidst them.  Consist of chloroplasts are termed chlorenchyma.  Consist of big air voids is called Aerenchyma , the main purpose is Buoyancy.  Some perform storage function , for storage in vegetable & fruits.  May appear as Secretory forms such as glandular & stinging hairs , nectaries & salt glands. 2 – Collenchyma :  These are stretched out , living cells with minute intercellular gaps.  These closely arranged. short or elongated in shape.  Their walls are made up of pectin & cellulose.  Found in marginal regions of leaves & stems  Offers flexibility to plants. 3 – Sclerenchyma :  Function : mechanical support (strength ) duo to thick lignified secondary walls , which contain large amount of cellulose & lignin.  At maturaty , some cells no longer have living protoplasts.  Found in the covering of seeds & nuts , around the vascular tissues in stems & the veins of leaves. TYPES OF SCLERENCHYMA : A – Fibers : Elongated with pitted wall.  Found in Xylem & Phloem , along leaf veins & margins surrounding vascular bundles in stems. B – Sclereiods : dense (lignified) short cells which may look like stones , rods , bones , stars or branched structures.  Found in nutshells fruit pits & the seed coats in legume tree pods (fabaceae). 10  Dr.Mohamed Elshebly Complex permament tissue (two types) : 1 – Xylem : composed of several types of cells (living & non living ). A. Non Living : Trecheary elements , composed of tracheids & vessel elements , which conduct water & nutrients.  Fibers , which provide support (aligned side by side ).  Vessel elements are aligned end to end to form long tube. B. Living : parenchyma , which store food. C. Scleroids may also be present. 2 – Phloem : sieve cells , sive elements , companion , scleroids , fibers , parenchyma & latex producing cells (Laticifiers )  Sieve cells : elongated , thin walled & minus a nucleus , found in conifers & primitive vascular plants such as ferns.  Sieve tube elements : are enucleated & found in more advanced flowering plants.  Both form long end-to-end columns called sieve tubes.  Sieve plates , consisting of primary pit fields , occur in the end walls of cell.  Seive cells containing many pores that allow for cell to cell solute transport. Companion cells : A specialized type of parenchyma , may be present in varying numbers in association with sieve tube elements. Special Tissues : modified structurally to carry out functions secretory in nature & are two types 1 – Laticiferous Tissues :  Have latex , cells are elongated , thin walled & multinucleated. 11  Dr.Mohamed Elshebly  Observed in families such as Euphorbiaceae , Apocynaceae & compositate etc.... 2 – Glandular Tissues :  They posses varios glands , that secrete oils , resins , tannins , mucilage , etc.  The gland is situated on epidermis. PLANT BODY ORGANIZATION : Plant organ system : 1 ---Shoot tissue system : The shoot : is the portion of the plant above roots & is composed of stems , leaves , flowers & fruits. A. Dermal Tissue System: - The outer layer of the apical meristem gives rise to the epidermis of the primary body. - In stems with secondary growth, the epidermis is replaced by periderm, commonly called ―outer bark. - Periderm consists of cork cambium producing cork (phellem) outward & the phelloderm inward. 12  Dr.Mohamed Elshebly B. Ground : - The cells of ground are derived from the apical meristem. - Ground tissue is manifest as cortex, located between epidermis & vascular bundles, & pith in center of the stem. C- Vascular: Derived from 2 tissues : 1-- Derived from apical meristem , the pro-cambium differentiate into A – Inside : primary xylem. B – Outside : primary phloem. 2 – In secondary growth derived from Vascular cambiam , which differentiate into : A – Inside : Secondary Xylem. B – Outside : Secondary Phloem. 2 --:Root Tissue system : A – Dermal tissue system :  with primary growth root covered by epidermis.  With secondary growth the epidermis & root hairs are removed because formation of periderm on outside. B – Ground tissue system : 1 – In primary growth : Cortex lies between the epidermis & vascular.  The innermost layer of the cortex endodermis which bound pericycle which surround primary vascular system. 2 -- In secondary growth : the cortex ( like the epidermis ) is Shed & replaced by periderm. 13  Dr.Mohamed Elshebly C – Vascular Tissue System :  IN the root ( unlike stem) : the primary vascular system (xylem + phloem ) arranged in alternate radial manner.  Xylem Arms radiate out from the center  Between xylem & phloem is procambium. Tissue Epidermis :  Usually single layer which cover leaves , stem , root & fruits. Cuticle : continuous layer at the outer surface of the epidermis which made up of fatty material (cuttin).  Epidermis some times overlaid with a protective , waterproof coating of wax , oil & salt crystals. FUNCTIONS OF EPIDERMIS : 1 – Mechanical support. 2 – Protection from dessication & against attack by pathogenic & Insects. 3 – Gas exchange. 4 – Restriction of water loss by evaporation (Transpiration ) through stomata. 5 – Storage of water & mineral. Shape :  Hexagonal , elongated or wavy margined.  In some plants such as those in grass family ( Poaceae) , have parallel rows of elongated cells alternating with short cells. 14 ‫‪Dr.Mohamed Elshebly‬‬ ‫يرى المتشائم الصعوبة في كل فرصة‪ ،‬أما المتفائل فيرى‬ ‫الفرصة في كل صعوبة‪.....‬‬ ‫أن تكون فرداً في جماعة الأسود خير لك من أن تكون قائداً‬ ‫للنعام‪.....‬‬ ‫‪.‬ستتعلم الكثير من دروس الحياة‪ ،‬إذا لاحظت أن رجال‬ ‫الإطفاء لا يكافحون النار بالنار‪.....‬‬ ‫‪GOOD LUCK ,,,,,‬‬ ‫‪Dr.Mohamed Elshebly ,,,,,,,,,,,‬‬ ‫‪15‬‬