Unit IV: Plant Anatomy (Structural organisation) Chapter 9 Tissue and Tissue System Learning Objectives The learner will be able to, Nehemiah Grew • Study major types of plant cells and Father of Plant their function. Anatomy • Differentiate the various types of 1641–1712 cells. • Study the relationship between the Katherine Esau (1898–1997) distribution of tissues in the various A legendary Role model for women in parts of plants. science. She was a scintillating Botany teacher and pioneering researcher for • Describes the ground tissue system six decades. Her classic book [cortex and pith] and vascular Anatomy is the best literature in systems of Seed Plants Plant Anatomy. In • Interpret cross sections and recognition of her longitudinal sections of dicot and distinguished service monocot root, stem and leaf. to science, she was • Compare the internal organization awarded National of dicot root and monocot root. Medal of Science (1989) by USA. This chapter introduces the internal structure of higher Plants. The study of Chapter Outline internal structure and organisation of 9.1 Meristematic tissue plant is called plant Anatomy (Gk: Ana = 9.2 Permanent tissues as under; temnein = to cut). Plants have cells as the basic unit. The cells are The tissue system 9.3 organised into tissues. The tissues in turn Epidermal tissue system 9.4 are organised into organs. The different Fundamental tissue system 9.5 organs in a plant have different internal Vascular tissue system 9.6 structures. It is studied by means of 9.7 Comparision of primary structure dissection and microscopic examination. 1 of tissue is called Histology. A plant is Milestones in Anatomy made up of different types of tissues. • 1837 Hartig: Coined the term Sieve There are two principal groups: tubes • 1839 Schleiden: Coined the term 1. Meristematic tissues 2. Permanent tissues Collenchyma • 1857 Hofmeister: Proposed Apical cell 9.1 Meristematic Tissue theory • 1858 Nageli. C: Coined the term 9.1.1 Characteristics and classification Xylem supporter and Phloem, Meristem and The characters of meristematic tissues: of Apical cell theory (Gr. Meristos-Divisible) • 1865 Mettenius: Coined the term The term meristem is coined by Sclerenchyma C. Nageli 1858. • 1868 Hanstein: Proposed Histogen • The meristematic cells are isodiametric theory and they may be, oval, spherical or • 1885 Tschirch: Coined the term polygonal in shape. Named Four types of Sclereids • They have generally dense cytoplasm (Brachy, Macro, Osteo & Sclereids with prominent nucleus. Astro) in 1889 • Generally the vacuoles in them are • 1914 Haberlandt: Coined the term either small or absent. xylem as and Phloem Hadrome as • Their cell wall is thin, elastic and Leptome and Classification of essentially made up of cellulose. meristem. • 1924 Schmidt A: Proposed Tunica – • These are most actively dividing cells. Corpus theory • Meristematic cells are self-perpetuating. • 1926 Schűepp: Mass, rib, & plate meristem Classification of Meristem • 1946 Bloch: Discovered the Meristem has been classified into several types on the basis of position, origin, Trichosclereids • 1952 Popham: Explained the function and division. organization of Shoot apex of Apical meristem Angiosperms • 1955 Duchaigne: Discovered the Annular collenchyma Intercalary meristem • 1961 Clowes: Proposed Quiescent centre concept • 1963 Sanio: Coined the term Tracheids Lateral meristem The Tissues A Tissue is a group of cells that are alike in Figure 9.1: Different types of meristems origin, structure and function. The study on the basis of position in plant body 2 Classification of Meristem Position Origin Function Plane of division Apical meristem Protoderm Mass meristem Present in apices of root Primary It gives rise to It divides in all and shoot. It is responsible Meristem epidermal tissue planes. Example: for increase in the length It is derived system and endosperm,young of the plant, it is called as from develops into embryo and primary growth. embryonic epidermis,stomata sporangium stages and and hairs. differentiated into primary Intercalary meristem permanent Rib meristem or Occurs between the tissues. Procambium File meristem mature tissues. It is It gives rise to It divides responsible for elongation primary vascular anticlinally in one of internodes. Secondary tissues. Example: plane. Example: It is xylem and phloem . development of meristem derived during cortex and pith Lateral meristem later stage of Occurs along the development longitudinal axis of stem of the plant Plate meristem and root. It is responsible Ground Meristem body. It It divides for secondary tissues and It gives rise to produces cork anticlinally in two thickening of stem and all tissues except planes. Example: cambium and root. Example: vascular epidermis and development of cambium and cork interfascicular vascular strands. epidermis cambium. cambium. Theories of Meristem Organization and Shoot Apical Meristem Function Apical Cell Theory Many anatomists illustrated the root Apical cell theory is proposed by and shoot apical meristems on the basis (1852) and supported by Hofmeister of number and arrangement and accordingly (1859). A single apical cell is the Nageli proposed the following theories – An structural and functional unit. extract of which are discussed below. Apical cell Tunica Leaf primodium Leaf primordia Dermatogen Periblem Histogen Corpus Plerome a. b. c. Shoot apical meristem a) Apical cell theory, b) Histogen theory, Figure 9.2: c) Shoot Tunica corpus theory 3 This apical cell governs the growth at their apices and the apical meristem and development of whole plant body. It is present below the root cap. The is applicable in Algae, Bryophytes and in different theories proposed to explain some Pteridophytes. root apical meristem organization is given below. Histogen Theory Apical Cell Theory Histogen theory is proposed by Hanstein Apical cell theory is proposed by (1868) and supported by The Nageli. Strassburgur. The single apical cell or apical initial shoot apex comprises three distinct zones. composes the root meristem. The apical 1. It is a outermost layer. Dermatogen: initial is tetrahedral in shape and produces It gives rise to epidermis. root cap from one side. The remaining 2. It is a middle layer. It gives Periblem: three sides produce epidermis, cortex and rise to cortex. vascular tissues. It is found in vascular 3. Plerome: It is innermost layer. It gives cryptogams. rise to stele Histogen Theory Tunica Corpus Theory Histogen theory is proposed by Hanstein Tunica corpus theory is proposed by and supported by . (1868) Strassburgur (1924). The histogen theory as appilied to the A. Schmidt root apical meristem speaks of four Two zones of tissues are found in apical histogen in the meristem. They are meristem. respectively 1. : It is the peripheral zone of The tunica i. It is a outermost layer. It shoot apex, that forms epidermis. Dermatogen: gives rise to root epidermis. 2. : It is the inner zone of The corpus ii. It is a middle layer. It gives shoot apex,that forms cortex and stele Periblem: of shoot. rise to cortex. iii. It is innermost layer. It gives Root Apical Meristem Plerome: rise to stele Root apex is present opposite to the shoot apex. The roots contain root cap iv. Calyptrogen: It gives rise to root cap. Epidermis Stele Cortex Cortex Stele Cortex Protoderm T Ground tissue Quiescent Vascular cambium Root centre cap Inverted ‘T’ division (Y division) Cap Plerome b. Calyptrogen c. Periblem Root apical meristem Dermatogen / Calyptrogen Figure 9.3: a) Histogen Theory, b) Korper kappe theory, Root cap c) Quiescent Centre Concept a. 4 Korper Kappe Theory Parenchyma (Gk: Para-beside; Korper kappe theory is proposed by enehein- to pour) Schuepp. There are two zones in root Parenchyma is generally present in all organs apex – Korper and Kappe of the plant. It forms the ground tissue in a 1. forms the body. plant. Parenchyma is a living tissue and made Korper zone up of thin walled cells. The cell wall is made 2. forms the cap. This Kappe zone up of cellulose. Parenchyma cells may be oval, theory is equivalent to tunica corpus polyhedral, cylindrical, irregular, elongated theory of shoot apex.The two divisions or armed. Parenchyma tissue normally has are distinguished by the type of T prominent intercellular spaces. Parenchyma (also called Y divisions). Korper is may store various types of materials like, characterised by inverted T divisions water, air, ergastic substances. It is usually and kappe by straight T divisions. colourless. The turgid parenchyma cells help Quiescent Centre Concept in giving rigidity to the plant body. Partial Quiescent centre concept was proposed conduction of water is also maintained by Clowes (1961) to explain root apical through parenchymatous cells. meristem activity. These centre is located between root cap and differentiating Intercellular spaces cells of the roots. The apparently inactive region of cells in root promeristem is called quiescent centre. It is the site of hormone synthesis and also the ultimate source of all meristematic cells of the meristem. 9.2 Permanent Tissues Parenchyma Figure 9.4: The Permanent tissues develop from apical Occsionally Parenchyma cells which meristem. They lose the power of cell store resin, tannins, crystals of calcium division either permanently or temporarily. carbonate, calcium oxalate are called They are classified into two types: idioblasts. Parenchyma is of different types 1. Simple permanent tissues. and some of them are discussed as follows. 2. Complex permanent tissues. Types of Parenchyma Simple Permanent Tissues Starch Simple tissues are composed of one type ggrains Intercellular of cells only. The cells are structurally and spaces functionally similar. It is of three types. 1. Parenchyma a. b. 2. Collenchyma Types of Parenchyma Figure 9.5: 3. Sclerenchyma a) Aerenchyma, b) Storage parenchyma 5 1. Aerenchyma: Parenchyma which contains air in its intercellular spaces. It helps in aeration and buoyancy. Example: . Nymphae and Hydrilla 5. Prosenchyma: 2. Storage Parenchyma: Parenchyma cells became Parenchyma stores food elongated, pointed and slightly materials. Example: Root and Parenchyma thick walled. It provides stem tubers. mechanical support. 4. Chlorenchyma 3. How?.... Stellate Parenchyma cells with Parenchyma chlorophyll. Function is Star shaped parenchyma. photosynthesis. Example: Example: Petioles of Banana Mesophyll of leaves. . and Canna small chloroplast or none. Tannin maybe Intercellular Intercellular Space Spaces present in collenchyma.Based on pattern Chloroplasts of pectinisation of the cell wall, there are Palisade Parenchyma three types of collenchyma Spongy Parenchyma Types of Collenchyma a. b. c. 1. Angular collenchyma It is the most common type of collenchyma c) Stellate parenchyma, Figure 9.5: with irregular arrangement and d) Chlorenchyma, e) Prosenchyma thickening at the angles where cells meets. Example:Hypodermis of Datura and Collenchyma (Gk. Colla-glue; Nicotiana enchyma – an infusion) Collenchyma is a simple, living mechanical 2. Lacunar collenchyma tissue. Collenchyma generally occurs in The collenchyma cells are irregularly hypodermis of dicot stem. It is absent arranged. Cell wall is thickening on the in the roots and also occurs in petioles walls bordering intercellular spaces. and pedicels. The cells are elongated Example:Hypodermis of Ipomoea and appear polygonal in cross section. The cell wall is unevenly thickened. 3. Lamellar collenchyma It contains more of hemicellulose and The collenchyma cells are arranged pectin besides cellulose. It provides compactly in layers(rows). The Cell wall is thickening is at tangential walls.These mechanical support and elasticity to the thickening appear as successsive tangential growing parts of the plant. Collenchyma layers. Example:Hypodermis of Helianthus consists of narrow cells. It has only a few 6 Diagramatic structures Nucleus Thickened Intercellular corners thickenings Protoplasm Vacuole Lamellar Cell wall thickenings a. b. c. Types of Collenchyma a) Angular collenchyma, b) Lacunar collenchyma, Figure 9.6: c) Lamellar collenchyma 1. Sclereids Duchaigne (1955) Annular Collenchyma: 2. Fibres reported another type called Annular collenchyma in petiole of Nerium. The Sclereids (Stone Cells) lumen is more or less circular in shape. Sclereids are dead cells, usually these are isodiametric but some are elongated Sclerenchyma (Gk. Sclerous- hard: too. The cell wall is very thick due enchyma-an infusion) to lignification. Lumen is very much The sclerenchyma is dead cell and reduced. The pits may simple or branched. lacks protoplasm. The cells are long or Sclereids are mechanical in function. short, narrow thick walled and lignified They give hard texture to the seed coats, secondary walls. The cell walls of these cells endosperms etc., Sclereids are classified are uniformly and strongly thickened. The into the following types. sclerenchymatous cells are of two types: Types of Sclereids 1. Branchysclereids or Stone cells: 2. Macrosclereids: Isodiametric sclereids, with hard cell Elongated and rod shaped cells, found in wall. It is found in bark, pith cortex, hard the outer seed coat of leguminous plants. endosperm and fleshy portion of some Example: Crotalaria and Pisum sativum. fruits. Example: - Pulp of Pyrus. 3. Osteosclereids (Bone cells): Rod shaped with dilated ends. They occur in leaves and seed coats. Example: seed coat of Pisum and Hakea 4. Astrosclereids: 5. Trichosclereids: Star cells with lobes or arms diverging Hair like thin walled sclereids. Numerous form a central body. They occur in petioles small angular crystals are embedded in the and leaves. Example: Tea, Nymphae and wall of these sclereids, present in stems and Trochodendron. leaves of hydrophytes. Example: Nymphaea leaf and Aerial roots of Monstera. 7 Diagramatic Structures Macro Sclereid Lumen Lumen cell Thick cell wall Lumen Thick cell wall Pith a. b. c. Thick Tricho cell wall Sclereids Lumen d. e. Types of Sclereids a) Brachysclereids, b) MacroSclereids, c) Osteosclereids, Figure 9.7: d) Astrosclereids, e) Trichosclereids Pointed pits. They provide The sclereids end Filiform Sclereids: m e c h a n i c a l are present in the leaf lamina of strength and Olea europaea. They are very much protect them elongated fibre like and about 1m.m from the strong length. wind. It is also called supporting tissues. Fibres Sclerenchyma Found in Some Fruits have a great commercial value in cottage and Lumen textile industries. Fibres are of five a) Pear fruit, Figure 9.8: types b) Strawberry, c) Guava T.S of fibre Figure 9.9 Wood Fibres or Xylary Fibres Fibres These fibres are associated with the Fibres are very much elongated secondary xylem tissue. They are also sclerenchyma cells with pointed tips. called xylary fibres. These fibres are Fibres are dead cells and have lignified derived from the vascular cambium. walls with narrow lumen. They have simple These are of four types. a. Libriform fibres 8 b. Fibre  tracheids c. Septate fibres Mesocarp Fibres d. Gelatinous fibres. Fibres obtained from the mesocarp of drupes like Coconut. Fibres are the longest Leaf Fibres plant cells. Longest Fibres obtained from the leaf of Musa, Fibres occur in Agave and Sensciveria. (Ramie Boehmeria fibre) 55 cm long Fibres in Our Daily Life Economically fibres may be grouped as a. These fibres have Libriform fibres: follows slightly lignified secondary walls with 1. Fibres utilized for the Textile Fibres: simple pits. These fibres are long and manufacture of fabrics, netting and narrow. cordage etc. b. These are shorter Fibre tracheids: a. : Example: Cotton. Surface Fibres than the libriform fibres with moderate b. : Example: Flax, Jute and secondary thickenings in the cell walls. Soft Fibres Ramie Pits are simple or bordered. c. Example: Sisal, c. Fibres that have thin Hard fibres: Septate fibres: Coconut, Pineapple, Abaca septa separating the lumen into distinct etc. chambers. Eg. Teak 2. Brush fibre: Fibres utilized for the manufacture of brushes and brooms. d. Fibres in which lignin Gelatinous fibres: is less in amount and cellulose is more in 3. Rough weaving fibres: Fibres utilized this cell walls. in making baskets, chairs, mats etc. 4. Wood fibres These fibres are characteristic of tension Paper making fibres: utilized for paper making. wood which is formed in the underside of leaning stems and branches. 5. Filling fibres: Fibres used for stuffing cushions, mattresses, pillows, furniture Bastfibres or Extra Xylary Fibres etc. Example: and Silk cotton. Bombax These fibres are present in the phloem. Natural Bast fibres are strong and Complex Tissues cellulosic. Fibres obtaining from the A complex tissue is a tissue phloem or outer bark of jute, kenaf, with several types of cells flax and hemp plants. The so called but all of them function pericyclic fibres are actually phloem together as a single unit. It fibres. is of two types – xylem and phloem. Surface Fibres These fibres are produced from the surface Xylem of the plant organs. Cotton and silk cotton The xylem is the principal water conducting are the examples.They occur in the testa tissue in a vascular plant. The term xylem of seeds. was introduced by (1858) and is Nageli 9 derived from the Gk. – wood. The Xylos Tracheids xylem which is derived from Procambium is Tracheids are dead, lignified and called and the xylem which primary xylem elongated cells with tapering ends. Its is derived from vascular cambium is called lumen is broader than that of fibres. In . Early formed primary secondary xylem cross section, the tracheids are polygonal. xylem elements are called protoxylem, There are different types of cell wall whereas the later formed primary xylem thickenings due to the deposition of elements are called metaxylem. secondary wall substances. They are Protoxylem lies towards the periphery annular (ring like), spiral (spring like), and metaxylem that lies towards the centre scalariform (ladder like) reticulate (net is called It is common in Exarch. roots. like) and pitted (uniformly thick except Protoxylem lies towards the centre and at pits). Tracheids are imperforated cells meta xylem towards the periphery this with bordered pits on their side walls. condition is called Endarch. It is seen in Only through this conduction takes place stems. in Gymnosperms. They are arranged one Protoxylem is located in the centre above the other. Tracheids are chief water surrounded by the metaxylem is called conducting elements in Gymnosperms . In this type only one vascular and Pteridophytes. They also offer Centrarch strand is developed. Example:  mechanical support to the plants. Selaginella sp. Protoxylem is located in the centre surrounded by the metaxylem is called .In this type several Mesarch vascular strands are developed. Example:  Ophioglossum sp. Student Activity Annular Spiral Reticulate Scalariform Pitted thickening students prepare the slide Cell lab: Types of secondary wall Figure 9.10: and identify the different types tissues. thickenings in tracheids and vessels Xylem Consists of Four Types of Cells Vessels or Trachea 1. Tracheids Vessels are elongated tube like structure. 2. Vessels or Trachea They are dead cells formed from a row of 3. Xylem Parenchyma vessel elements placed end to end. They 4. Xylem Fibres are perforated at the end walls. Their lumen is wider than Tracheids. Due to is called the dissolution of entire cell wall, a single Xylem hadrome phloem is called These terms are pore is formed at the perforation plate. leptome. coined by haberlandt (1914) It is called simple perforation plate, Example: . If the perforation Mangifera 10