The document discusses the structure and types of plant cell walls and tissues. It begins by describing the four layers of the plant cell wall: middle lamella, primary wall, secondary wall, and tertiary wall. It then discusses the ultrastructure of cell walls under electron microscopes. The document also covers the structure and functions of the plasma membrane, pits, plasmodesmata, and the four main types of plant tissues: meristematic tissues, parenchyma tissues, collenchyma tissues, and sclerenchyma tissues. It provides detailed information on each tissue type.

1. PLANT ANATOMY AND MICROTECHNIQUES
Unit 1
Structure of plant cell wall
 Plant cell is distinguished from the animal cells
 Cell wall is a outermost covering layer of plant cell
 It is absent in animal cell
 Each cell has own cell wall
 Thickness in relation to age and type of cells
 Generally, young cells have thin, elastic, transparent and
colourless
 The Cell wall itself is taken as the non-living part of the
cells
 It maintain the shape of cell
 Protects the protoplasm form external injuries
 Permeable to water
 Cell wall is made up of cellulose, hemicelluloses and
pectin
 The cell wall consists of four layers, it differ from one
another in physical and chemical nature
1. Middle lamella
2. Primary wall
3. Secondary wall
4. Tertiary wall
1. Middle lamella
 Outer most layer of cell wall
 Union of the primary walls of the two adjacent cells,
called Intercellular substance
 Made up of pectin, mixture of calcium and magnesium
 Cells of wood is deposited lignin
2. Primary cell wall
 First formed wall layer
 Formed form developing cells
 Present either side of the middle lamella
 Associated with living protoplasm
 Made up of cellulose, noncellulosic polysaccharides,
hemicelluloses and pectin
 Some cells present lignin
3. Secondary wall
 Appeared after the primary wall
 Made up of cellulose, noncellulosic polysaccharides
and hemicellulase
 Lignin also deposit
 Much thicker than primary wall
 Devoid of protoplast at maturity
 Active in living protoplast- xylem ray and xylem
parenchyma cells
Figure 1: Structure of cell wall
Figure 2: Wall formation
Figure 3: Piece of tracheid wall
showing structure of secondary wall

2.  It consist of three layers
a. Outer – SW1
b. Middle – SW2
c. Inner - SW3
 It vary on orientation of microfibrils
 Maintain the cells shape and mechanical strength
4. Tertiary wall
 Present innerside of secondary wall
 dried residue of degenerating plasmamembrane
 Rarely present
Ultrastructure of cell wall
 The cell walls under the electron microscope shows
two parts
 Matrix- non cellulosic part
 Fibrils- embedded in the matrix and made
up of cellulose
 The largest fibril could be seen by a light microscope
and is called a macrofibril
 The smaller ones are seen under the electron
microscope and are called microfibrils
 With the increase in resolving power smaller and
smaller fibrils are visualized as subunits of microfibrils
 These are called micells which in turn are further divided to form cellulose molecules
 The microfibrils display a dense textile like pattern in electron microscope preparation
Plasma membrane or plasmalemma
 There is present a living membrane called plasma membrane or plasmalemma in all the plant and animal
cells around the cytoplasm
 Like other membranes it is also a unit membrane or 100 Aº thickness
 The unit membrane contains about 40% lipid and 60% protein
 It consists of a bi-molecular layer of phospholipids (40-60 Aº dia) with their not polar oriented inwardly
perpendicular to the plane of the membrane
 The external surface of the double layer is made up of phospholipids on the both side of the polar moieties
and is covered by a layer of protein
Functions
 Controls cellular semipermeability, resorption and excretion acting in a selective pathway manner
 Protective function
 The material inside or outside the plasma membrane could be transported pinocytosis or phagocytosis.
 The plamma membrane invaginates to form vacuole which passes sinto the cell to form food vacuole or
phagocytic vacuole
 By reverse process material is thrown out of plasma membrane
Figure: Ultra structure of cell wall

3. Chemical nature of cell wall
1. The cell wall is composed of carbohydrate rich
materials
2. The major component of cells are
cellulose, hemicelluloses, pectins, proteins
and phenolics
a. Cellulose
 Provides shape and strength of cell wall
 Hydrophilic crystalline compound
 Long chain of linked glucose residues, more
than 100
 Molecules are Chain or ribbon like structure
 General formula is (C6H10O5)n
 Cellulose is an unbranched β 1,4-glucan
b. Non cellulosic polysaccharides / hemicellulose
 Closely allied to cellulose
 Built up of a variety of different sugars
Examples:
Xylan:
 Linked with xylose and arabinose
 Primary and secondary wall of dicot plants
Glucomannan:
 Secondary wall of gymnosperm and
angiospermous cells
 Glucose and mannose in the ratio of 1:3
Mannan and Galactomannan:
 Found in wall of endosperm
 Reserves food
Glucuronomannan:
 Low proportion in the cell walls
 Contain mannose, glucuronic acid, xylose
and arabinose
Xyloglucan:
 Storage polysaccharides
 Xyloses are major components
 It also contain glucose
 Thick storage wall in some seeds, eg.
Nasturtium
 Present in primary wall of dicot and grasses
 Absent in secondary wall
 Backbone of cellulose
c. Pectin
 Derivative of polyglacturonic acid
 Rich in galacturonic acid
 Linked to cellulose, proteins and phenols
 Present in primary and secondary walls
 High concentration in middle lamella
 Highly hydrophilic polysaccharides
 Necessary for wall expansion
d. Lignin and other phenolic compounds
 Organic compound of high carbon content
 Component of scelerenchyma, fibres,
sclereids
 Also found in tracheids and vessels of
xylem
 The process of conversion of cellulose into
lignin is called as lignification
e. Cutin, suberin and waxes
 These are fatty substances
 Cutin found in walls of roots, stem and
leaves
 Suberin deposited in seed coats, cork and
casparian strips
 Wax occurs in surface of leaves and fruits
f. Gum and mucilages
 Compounds of carbohydrates related pectin
 Posses the property of swelling in water
 Gums appear in breakdown of walls
 Mucilages found in seed coat, increase the
water holding capacity
g. Mineral substances
 Like silica, calcium carbonate, calcium
oxalate and several organic compounds
may deposit on cell wall
 Silica found in Equisetum
 Calcium carbonate noted in Ficus

4. Plasmodesmata
1. The cytoplasm of the two neighbouring cells is interconnected through fine protoplasm threads called
Plasmodesmata (singular: Plasmadesma)
2. Plasmodesma is thin irregular cylinder of cytoplasm lined by plasmolemma, forming fine pores in the cell
wall
3. Plasmodesma originates during cytokinesis when cell plate is formed
4. These strands bind together to protoplast of the neighbouring cells into a large called symplast and
facilitate the movement of food and information, form once cell to another cell
5. The plasmodesma have been seen in red algae, liverworts, mosses, vascular cryptogams, gymnosperms
and angiosperms
6. They found throughout all living tissues of a plant including the meristematic tissue
7. Plasmodesma either occur in groups or are distributed throughout a wall
8. In groups are mostly found in the primary pit fields
9. Plasmodesma exists in thick cell also, eg. endosperm of the seeds Phoenix, Coffea
10. The plasmodesma are also regarded as channels permitting the movement of viruses from cell to cell
11. Plant hormones move through plasmodesma
12. The movement through palsmodesma is bi-directional, desmotubules act as a valve and regulate the
direction of flow
13. small molecules and ions pass readily through plasmodesma
Figure: Plasmodesma between adjoining cell walls

5. Pit
 The entire inner surface of the cell wall is thickened, leaving small unthickened areas or depressions here
and there, called as the pits
 The pits are formed in pairs lying against each other on the opposite sides of the wall, and morphologically
more correct they are called pit pairs
Structure
 The space found inside the pit is called the pit cavity or pit chamber.
 The separating membrane which separates the two chambers or cavities of a pit pair, is called the pit
membrane, or pit aperture
 The pit cavity opens internally in the lumen of the cell and is closed by the closing or pit membrane along
the line of junction of two contiguous cells
 A pit pair has two pit cavities, two pit apertures, and one pit or closing membrane
 The pit membrane is common to both pits of a pit pair and consists of two primary walls and a middle
lamella or intercellular substance
 Two types of pits are met with in the cells of various plants viz
 Simple pits
 Bordered pits
 Two bordered pits make up a bordered pit pair
 Two simple pits form a simple pit pair
 A bordered pit and a simple pit lying opposite to each other in contiguous cells, constitute a half bordered
pit pair
 A pit occurs opposite an intercellular space has no complementary pit and is known as blind pit
a. Simple pits
 Simple pit pairs occur in parenchyma cells, in medullary rays, in phloem fibres, campanion cells, and in
tracheids of several flowering plants
 In simple pits, the pit cavity remains of the same diameter and the pit or closing membrane also remains
same and uniform in its structure
 The simple pit may be circular, oval, polygonal, elongated or somewhat irregular in its facial view
b. Bordered pits
 They are abundantly found in the vessels of many angiospers and in the tracheids of many conifers
 They are more complex and variable in their structure than simple pits
 The overarching secondary wall which encloses a part of the pit cavity is called the pit border
 The opens outside by a small rounded mouth known as pit aperture
 The overarching rim forms a border around the aperture and thus named bordered pits
Figure: Pits. A Surface view of simple pits, B Simple pit pairs in section
C Surface view of bordered pits, D Bordered pit pairs in section

6. Tissue system
A. Meristematic tissues
 Meristematic tissue consists of thin-walled, tightly packed living cells
 Occurs frequent cell division
 Undergo cell division and wall formation followed by differential cell expansion
Classification of meristems
 Basis of different characters like
 Origin
 Stage of development
 Position in plant body and
 Functions
1. Meristems based on origin
 Two types
a) Primary meristems
b) Secondary meristems
a) Primary meristems
 Present from embryonic stage
 Persist throughout the life of a plant
 Known as primary mersitems
 Forms primary or fundamental part of the plant body
 Present in the apices of stem and root, primordial of leaves and similar organs
b) Secondary meristems
 Arise from non-meristematic or permanent tissue
 Cork cambium forms the typical example of secondary meristem
 Developed from mature cells of epidermis, cortex or pericycle
 Vascular cambium in stem is partly a secondary meristem
 Fsicular cambium it developes form the cells of ground tissue (medulary ray cells)
2. Meristems based on plan of cell division
 There types
a) Mass meristem
b) Plate meristem
c) Rib meristem
a) Mass meristem
 Exhibits division in all planes
 Results increased in volume
 Example- development of pith, cortex, endosperm etc
b) Plat meristem
 Cells divide in two planes
 Increase in area of the organ

7.  Results in the formation of flat structures
 Examples- epidermal growth and leaf
formation
c) Rib meristem
 Cell division is in one plane
 Results in the formation of row of cells
 Example- formation of young roots, pith and
cortex of young stems
3. Meristems based on position in plant body
 Three types
a) Apical meristem
b) Lateral meristem
c) Intercalary meristem
a) Apical meristem
 Existent at the growing tips or apical of stems
and roots
 Apical meristem upsurges the length of the
plant
b) Lateral meristem
 Existent in the radial portion of the stem or
root
 Lateral meristem upsurges the thickness of the
plant
c) Intercalary meristem
 Found at the internodes or at the base of the
leaves
 Intercalary meristem upsurges the size of the
internode
4. Meristems based on function
 The promeristem, the first formed meristem
 Promeristem differentiated into three regions
a) Protoderm- outermost and forms the epidermis
b) Procambium- rise to the primary vascular tissues (phloem, cambium and xylem)
c) Fundamental or ground meristem- primary cortex, pericycle, primary medullary rays and pith
 These layers have distinct functions
Figure: Longitudinal (L.S.) and transverse
section (T.S.) of meristems

8. B. Permanent tissues
 Cells which have lost their ability to distribute but are specialized to offer elasticity, flexibility and
strength to the plant
 The cells of these tissues may be living or dead and thin walled or thick walled.
 These tissues can be categorized into
1. Simple Permanent Tissue
 Simple tissue classified into
a) Parenchyma
b) Collenchyma and
c) Sclerenchyma
2. Complex Permanent Tissue
 Complex tissues include phloem and xylem.
 Xylem is valuable for the transportation of water and solvable constituents.
 Xylem is made up of
a) Xylem parenchyma
b) Fibres
c) Vessels and
d) Tracheids
 Phloem is valuable in the transportation of food particles
 Phloem consists of
a) Phloem parenchyma
b) Phloem fibres
c) Companion cells and
d) Sieve tubes
1. Simple tissue
A. Parenchyma
 These are alive
 Thin-walled, polyhedral or otherwise variously shaped, sometimes lobed
 Present intercellular spaces
 Parenchymatous cells create ground tissue and pith
 Further categorized into
a. Chlorenchyma
 Parenchyma comprising of chloroplasts are termed as chlorenchyma
 The chlorenchyma helps in photosynthesis
Figure: Types of parenchyma cells

9. b. Aerenchyma
 Aerenchyma is a specialized parenchymatous tissue
 Occurs in aquatic plants (hydrophytes).
 It possesses a regular, well developed system of large intercellular air spaces
 It facilitates internal diffusion of gases.
 Associated with a system of transverse septa or diaphragms that provide mechanical resistance
 Some parenchymatous cells perform as storage chambers for starch in vegetable and fruits
C. Collenchyma
 Collenchyma consists of axially elongated, tightly packed cells with unevenly thickened walls.
 This tissue has a strengthening function
 Collenchyma cells differ from fibres in that they often retain
 Their cell walls are made up of pectin and cellulose
 Collenchyma is found in the marginal regions of leaves and stems
 Offers flexibility with the structural framework and mechanical support in plants
Figure: Types of collenchyma cells
D. Sclerenchyma
 Sclerenchyma, also a supporting or protective tissue
 Consists of cells with thickened, often lignified, walls, which usually lack contents at maturity
 Sclerenchyma cells occur in primary or secondary tissue
 They have no intercellular gaps
 Sclerenchyma is found in the covering of seeds and nuts
 Present around the vascular tissues in stems and the veins of leaves
 Sclerenchyma provides strength to the plant
 They are categorized as either fibres or sclereids
a. Fibres
 Fires are very much elongated and narrow cells with pointed ends
 walls are very thick with reduced cavity and cells are dead at maturity
 Thickening is due to the thick secondary wall
 Imparts strength to the fibre bundles
 Based on position the fibres are
i) Wood fibres or xylem fibres- long cells with lignified secondary walls
ii) Phloem fibres or bast fibres or extraxylary fibres- found in stems, originate in the early
part of phloem tissue
b. Sclereids
 Known as stone of cells or sclerotic cells
 These are widely distributed in the plant body

10.  Shape and size are variable
 Very thick secondary walls, strongly lignified
 Lumen is very much reduced
 Classified into
i) Brachysclereids- stone cells or scelerids are short and more or less isodimetric
ii) Macrosclerids- rod shaped or columnar
iii) Osteosclereids- bone shaped, columnar with enlarged ends
iv) Astrosclerids- star shaped
v) Trichosclereids- branched hair like
Figure: L.S. and T.S. of Sclerenchyma fibres Figure: Types of sclereids
2. Complex tissue
 Vascular tissues have been treated as complex tissues
a. Xylem and
b. Phloem
A. Xylem
 Xylem is a conducting tissue
 It helps in the transport of dissolved substances and water all through the plant
 Xylem is composed of different kinds of elements
 They are
i. Tracheids
ii. Vessels
iii. Wood fibres and
iv. Wood parenchyma
i) Tracheids
 Elongated cell with tapering ends (one side)
 Dead cells and lacking protoplast at maturity (like empty lumen)
 Walls are hard and lignified
 Angular, may be rounded
 Thickening may be annular, spiral, scalariform in primary xylem
 Pitted in secondary or metaxylem
 Passage of water from cell to cell is facilitated by pit pairs
 The function is conduction and storage
 Important role in supporting of an organ

11. ii) Vessels
 Cylindrical tube-like structures found in wood of angiosperms
 Formed by absorption of the end walls from row of procambium cells placed end to end
 The mature cells have no protoplasm and the wall are lignified
 The cell walls have various types- annular, spiral, scalariform, reticulate and pitted
 The function is water conduction and mechanical support
iii) Wood fibres (xylem fibres)
 Integrate part of the xylem
 Consist of long, slender, pointed, dead and sclerenchymatous cells
 Fibres are usually very long and narrow cells with tapered or branched ends
 Two types based on wall thickness type and amount of pits
a. Libriform fibres- extremely thick walls and simple pits
b. Fibre tracheids- medium thickness, bordered pits
 The function of wood fibres provide mechanical strength to specified parts
 Commercial uses- textile industry, cordage industry, brush fibres and filling fibres
iv) Wood parenchyma (xylem parenchyma)
 More are less elongated, placed end to end and may be thick or thin walled
 Usually present in the secondary xylem is thick walled due to lignifications
 Xylem remain alive as long tissue
 The function is conduction of water upward directly or indirectly
 Helps in storage of food materials
Figure: Xylem tissue
B. Phloem
 This tissue helps in the transportation of food all through the plant.
 The diverse elements of phloem include
i. Sieve elements
ii. Companion cells
iii. Phloem fibres and
iv. Phloem parenchyma
 The basic cell type is sieve elements
i) Sieve elements
 Conducting elements of phloem are known as sieve elements
 Segregated into less specialized sieve cells and more specialized sieve tubes or sieve tube elements
 Sieve areas each connecting strand enclosed in cylinder of substance called callose

12.  The wall is double structure consisting of two layers of primary wall
 Wall parts bearing highly specialized sieve areas are called sieve plats
 The conduction of food materials takes place through cytoplasmic strands
ii) Companion cells
 Specialized type of parenchyma cell, closely associated in origin, position and function with sieve tube
elements
 Small, triangular, rounded or rectangular cell beside a sieve tube element
 Cells are living, abundant granular cytoplasm, prominent elongated nucleus
 This is retained throughout the life of cell, do not contain
starch
iii) Phloem fibres
 Form a prominent part of both primary and secondary
phloem in flowering plants
 Rarely found or absent in phloem of living pteridophytes,
also in gymnosperms
 Walls may be lignified or non-lignified
 Associated with sclerenchyma and phloem
 Among four phloem elements, phloem fibres are only
dead tissue
iv) Phloem parenchyma
 Contains parenchyma cells
 Concerned with many activities such as storage of starch,
fat and other organic substances
 Found tannins and resins
 Elongated and are oriented, like the sieve elements
 Two systems of parenchyma found in the secondary
phloem- vertical and horizontal
 Horizontal parenchyma is composed of phloem rays
Figure: Phloem tissue

13. C. Secretory tissues
 The substances separated from the protoplast are deposited
 in the non-living cells,
 in vacuoles of the living cells,
 in cavities or in canals
 This phenomenon is called secretion
 Secretory tissues are the cells or glands concerned with the secretion of
 Gums,
 Resins,
 Terpenes,
 Tannins,
 Essential oils,
 Nectors or
 Hormones etc.
 These are further subdivided into two groups
a. Laticiferous tissues
b. Glandular tissues
a. Laticiferous Tissues
 Latex is present in the family of many flowering plants
 Substance like sugars, proteins, gums, alkaloids, enzymes, rubber etc.
 Substance may be white, yellow or pinkish in colour
 Viscous fluid and established to the colloidal in nature
 These are of two kinds
i) Latex vessels and
ii) Latex cells
i) Latex vessels
 Formed by the fusion of walls of many cells and the dissolution of septa
 Living and possess lateral branches, coenocytic structure
 Called as articulated laticifers
 Found in Papaveraceae, Cactaceae, Musaceae and Aroideae etc.
ii) Latex cells
 Similar in shape to the vessels
 Elongated and branched individual cells
 Contain numerous nuclei and secrete latex
 The branches in this case do not anastomose
 Called non-articulated laticifer
 Found in Urticaceae, Asclepidaceae, Moraceae, Euphorbiaceae and Apocynaceae
b. Glandular Tissues
 Special structures contain some secretory or excretory products
 Consist of isolated cells or small group of cells with or without central cavity
 Various kinds and more common types are secrete digestive enzymes called digestive glands
 Secrete nectar, known as nectarines
 They may be
 Internal- lying embedded in inferior tissues are oil glands, mucilage, gums, resin and tannin
digestive glands secreting enzymes, water secreting glands, known as hydathodes
 External- occur on the epidermis are glandular epidermal hairs, nectarines

14. i) Digestive glands
 Secrete digestive enzymes in certain insectivorous plants
 Secrete protein digesting enzyme and viscid substances to hold insects
ii) Oil glands
 Secrete essential oils in leaves and fruits of orange and lemeon
 These oils are volatile and odoriferous
iii) Mucilage secreting glands- Betel leaf
iv) Glands secreting resins, gums etc- Gymnosperms and many angiosperms family
v) Water secreting glands (Hydathodes)
 Special organs through which exudation of water mixed salts takes place
 Present at the tip or margins of leaves of plants that grow in moist places
 Known as hydathodes or water stomata
vi) Nectaries
 Insect-pollinated plants produce nectar
 Which is attracts insects
 Substance is secreted by special cellular structures
Figure: Secretory tissues. A Hydathodes, B Glandular hair, C Stinging hair, D-F Nectary, G Digestive gland

15. Trichomes or hairs
 The epidermal cells of most plant, grow out in the form of hairs or trichomes
 Found singly or less frequently in groups
 Unicellular or multicellular and occur in various forms
 Vary from small protuberances of epidermal cells to complex branched or stellate multicellular structures
 Hairs may be dead or living
 Loss their protoplasm in their cells
 The hairs may be several types
 Stinging hairs
 Laticiferous hairs
 Bladder like hairs
 Mucilage hairs
 Arachnoid hairs
 Calcified or silicified hairs
 Non-glandular shaggy hairs
 Glandular shaggy hairs
 Non-glandular tufted hairs
 Two-armed non-glandular hairs
 Stellate glandular hairs
 Branched non-glandular hairs
 Branched glandular hairs
 Capitate sessile hairs
 Glandular capitates stalked hairs
 Non-glandular peltate hairs
 Glandular peltate hairs and
 Uniseriate hairs
 Trichomes may be classified into different morphological categories
 Common type is referred to as hair
 Hairs may be subdivided into
 Unicellular- branched or unbranched
 Multicellular-consist single row of cells or several layers
branched in dendroid (tree-like) or branches oriented largely in one plane (stellate hairs)
 Important types are
a. Stinging hairs
 Most interesting types of trichomes
 contains poisonous liquid and consists of a basal bulb like portion
 Stiff, slender and tapering structure
 Tapering structure ends in a small knob like or sharp point
b. Glandular hairs
 Secrete oil, resin or mucilage
 Possesses a stalk and enlarged terminal portion, referred to as gland
 Uni- or multicellular hairs
 Dense protoplast and elaborate various substances like volatile oils, resins, mucilages and gums
 Substances are excreted and accumulate between the walls and cuticle
c. Scale or pelate hair
 Common type of trichome is the scale, also called pellate hair
 Scale consists of discoid plate of cells
 Borne on a stalk or attached directly to the foot

16. Figure: Different types of trichomes
Cell wall
 Trichomes are commonly or cellulose and covered with a cuticle
 May be lignified, produce thick secondary walls
 Sometimes impregnated with silica or calcium carbonate
 Cystoliths and other crystals may develop in hairs
Functions of trichomes
 Dense covering of wooly trichomes control the rate of transpiration
 Reduce the heating effect of sunlight
 Protection of plant body from outer injurious agencies
 Insectivours plants give enzymes
 Present on seeds these are helpful in dispersal

17. Unit 2
Anatomy of dicot stem
Epidermis
1. Outermost layer of the stem
2. Surrounded by a well-defined cuticle
3. Single-layered
4. Develop multicellular epidermal hair
5. Epidermal layer is broken by certain stomata
Cortex
6. Consists of outer collenchyma, some parenchyma
7. Collenchyma region is 3 to 6 layered, cells are thickened due to the deposition of pectin and cellulose
8. Parenchyma is present inner to the collenchymas, contains many intercellular spaces
9. Innermost layer of cortex is is endodermis contain casparian strips and starch grains
Pericycle
10. Sclerenchymatous, outside the phloem of each vascular bundle
Vascular Bundles
11. Conjoint, collateral, open and endarch
12. Arranged in a ring, and each consists of phloem, cambium and xylem
13. Phloem consists, of sieve tubes, companion cells and phloem parenchyma
14. Cambium is present in between xylem and phloem
15. Xylem consists of vessels, tracheids, wood fibres and woody parenchyma
16. Big xylem vessels represent metaxylem and smaller is protoxylem
Pith
17. Present in the centre consists of thin walled, rounded or polygonal, parenchymatous cells
Figure: Transverse section of Dicot Stem

18. Anatomy of monocot stem
Epidermis
1. Outermost layer
2. Made up of single layer of tightly packed parenchymatous cells
3. Present thick cuticle
Hypodermis
4. Few layers of sclerenchymatous cells lying below the epidermis
5. Gives mechanical strength
Ground tissue
6. It is not differentiated into cortex, endodermis, pericycle and pith
7. Loosely arranged parenchyma cells
8. Present intercellular spaces
9. Storage layer of food
Vascular bundles
10. Scattered in the ground tissue
11. Vascular bundles are numerous, small and closely arranged in the peripheral portion
12. Towards the centre, the bundles are large in size and loosely arranged
13. Each vascular bundle is surrounded by a sheath of sclerenchymatous fibres called bundle sheath
14. The vascular bundles are conjoint, collateral, endarch and closed
15. Phloem consists of sieve tubes and companion cells
16. Phloem parenchyma and phloem fibres are absent.
17. Xylem are two metaxylem vessels are located at the upper two arms
18. The one or two protoxylem vessels at the base. (Y shaped)
Figure: T.S. of Monocot stem

19. Anatomy of dicot root
Rhizodermis or epiblema (Epidermis)
1. Outermost layer
2. Made up of single layered
3. Parenchymatous cells
4. Wthout intercellular spaces
5. Stomata and cuticle are absent
6. Root hairs are always single celled
Cortex
7. Oval or rounded and loosely arranged cells
8. Parenchymatous
9. Cells are stored food
Endodermis
10. Made up of single layer of barrel shaped
parenchymatous cells
11. Radial and the inner tangential walls are
thickened with suberin
12. Thickenings are known as casparian strips
13. Casparian strips are absent in opposite to the
protoxylem
Stele
14. All the tissues present inside endodermis
comprise the stele
Pericycle
15. Single layered
16. Parenchymatous cells
17. Found inner to the endodermis
18. Lateral roots originate from the pericycle
Vascular system
19. Radial arrangement
20. Xylem and phloem are separated by
conjunctive tissue
21. Xylem is exarch and tetrarch condition
22. Metaxylem vessels are generally polygonal
in shape
Pith
23. Absent
Figure: Transverse section of Dicot root

20. Anatomy of monocot root
Rhizodermis or epiblema (Epidermis)
1. Outermost layer
2. Parenchymatous cells
3. Without intercellular spaces
4. Stomata and cuticle are absent
5. Root hairs are always single celled
Cortex
6. The cortex is homogenous
7. Consists of oval or rounded and loosely
arranged cells
8. Parenchymatous
9. Function is storage.
Endodermis
10. Single layer of barrel shaped
11. Parenchymatous cells
12. Radial and inner tangential walls are thickened
with suberin,
13. Thickenings are known as casparian strips.
14. Casparian strips are absent in opposite to the
protoxylem
Stele
15. All the tissues present inside endodermis
comprise the stele
Pericycle
16. A single layer of parenchymatous cells
17. Found inner to the endodermis
18. Lateral roots originate from the pericycle
Vascular system
19. Radial arrangement.
20. Xylem and phloem are separated by
sclerenchymatous conjunctive tissue
21. Xylem is exarch and polyarch condition
22. Metaxylem vessels are generally circular in
shape
Pith
23. The central portion is occupied by a large pith
24. It consist of thin walled parenchyma cells with intercellular spaces
25. Cells are filled with starch grain
Figure: Transverse section of Monocot root

21. Unit 3
Normal secondary thickening in dicot stem
 Secondary growth is the formation of secondary
tissues
 It increases the diameter of the stem
 They take part in providing protection,
 Support and
 Conduction of water and nutrients
 Secondary tissues are formed by two types of
lateral meristems
a. vascular cambium and
b. cork cambium or phellogen
I. Formation of Secondary Vascular Tissues
 They are formed by the vascular cambium.
 Vascular cambium is produced by two types of
meristems
i. Fascicular or intra-fascicular occurs as
strips in vascular bundles
ii. Inter-fascicular cambium arises secondarily
from the cells of medullary rays
 These two types of meristematic tissues get
connected to form a ring of vascular cambium.
 Vascular cambium divide periclinally both on
the outer and inner sides (bipolar divisions) to
form secondary permanent tissues
 The cells of vascular cambium are of two types
 Elongated spindle-shaped fusiform initials and
 Shorter isodiametric ray initials
 Fusiform initials divide to form secondary
phloem on the outer side and secondary xylem
on the inner side
 The formation of secondary xylem on the inner
side
 The vascular cambium moves gradually to the
outside by adding new cells.
 The phenomenon is called dilation. New ray
cells are also added
a. Vascular Rays
 The vascular rays or secondary medullary
rays are rows of radially arranged cells
 Which are formed in the secondary vascular
tissues.
b. Secondary Phloem (Bast)
 It forms a narrow circle on the outer side of
vascular cambium.
 Secondary phloem does not grow in
thickness
c. Secondary Xylem:
 It forms the bulk of the stem and is commonly called wood.
 Secondary xylem does not show distinction into protoxylem and meta-xylem
Figure: Normal secondary thickening in dicot stem

22. d. Annual Rings (Growth Rings)
 Annual rings are formed due to sequence of rapid growth (favourable season, e.g., spring), slow growth
(before the onset of un-favourable period, e.g., autumn) and no growth (un-favourable season, e.g.,
winter)
e. Spring wood and Autumn wood
 It is the wood formed in a single year.
 It consists of two types of wood, spring wood and
autumn wood.
Spring wood
 The spring or early wood is much wider than the
autumn or late wood.
 It is lighter in colour and of lower density.
 Spring wood consists of larger and wider xylem
elements.
Autumn wood
 The autumn or late wood is dark coloured and of
higher density.
 It contains compactly arranged smaller and
narrower elements which have comparatively
thicker walls.
Sapwood and Heartwood
 The wood of the older stems (Dalbergia, Acacia) gets differentiated into two zones,
 The outer light coloured and functional sapwood or alburnum
 The inner darker and nonfunctional heartwood or duramen
II. Formation of Periderm
 Increase in girth and prevent harm on the rupturing of the outer ground tissues due to the formation of
secondary vascular tissues
a. Cork cambium or phellogen
 Dicot stems produce a cork cambium or phellogen in the outer cortical cells
 Phellogen cells divide on both the outer side as well as the inner side
b. Secondary cortex or phelloderm
 Secondary tissue produced on the inner side of the phellogen is parenchymatous or collenchymatous
 It is called secondary cortex or phelloderm.
 Its cells show radial arrangement.
c. Cork or phellem
 Phellogen produces cork or phellem on the
outer side.
 It consists of dead and compactly arranged
rectangular cells
 Possess suberised cell walls.
 The cork cells contain tannins
 They appear brown or dark brown in colour
d. Lenticels:
 Lenticels are aerating pores in the bark of
plants.
 They appear on the surface of the bark
 Containing oval, rounded or oblong depressions
 They are facilitating gas exchange.
e. Bark
 All the dead cells lying outside phellogen are collectively called bark.
Figure: Extra-stelar growth in dicot stem

23. Normal secondary thickening in dicot root
 The roots of some herbaceous and woody dicotyledons show secondary increase in thickness
 Dicotyledonous roots show secondary growth in thickness
 Similar to that of dicotyledonous stems
 The roots have limited number of radially arranged vascular bundles with exarch xylem.
 Pith is usually absent.
 A few parenchyma cells beneath each phloem, meristematic and thus form strips of cambium
 The number of strips being equal to the number of phloem present.
 Cambial cells divid and produce secondary tissues.
 The cells of pericycle against the protoxylem
 The first- formed cambium now extends both ways
 Cambium reaches the innermost xylem.
 The cambial cells produce more xylem than phloem
 The first-formed cambium produce secondary xylem more rapidly
 The cambium cylinder is circular.
 The secondary vascular tissues are fundamentally similar to those of the stem.
 The root structure is radially arranged, exarch primary xylem located at the central region
 The strands of secondary vascular tissues being collaterally arranged like stem
 The sieve elements of the primary phloem often get crushed.
 The cambial cells originating from the pericycle against protoxylem
 It produces broad bands of vascular rays.
 These rays running between xylem and phloem through the cambium
 They are also called main medullary rays.
 Periderm is formed in the outer region.
 Phellogen arises in the outer cells of the pericycle
 It produces phellem or cork cells on the outer side, and phelloderm on the inner.
 The pressure caused by formation of secondary tissues inside the cortex with endodermis
 Lenticels may be formed.
Figure: Normal secondary thickening in dicot root

24. Anomalous secondary growth in
Boerhaavia stem
Epidermis:
1. Single layered, small, radially elongated cells.
2. Multicellular epidermal hairs
3. A thick cuticle is present on the epidermis.
Cortex:
4. Well differentiated and consists of few layered
collenchymatous hypodermis followed by
chlorenchyma.
5. Collenchyma is 3 to 4 cells.
6. Chlorenchyma is present inner to collenchyma
in the form of 3 to 7 layers.
7. Chlorenchymatous cells are thin walled, oval,
full of chloroplasts and many intercellular
spaces.
8. Endodermis is clearly developed and made up
of many, tubular, thick-walled cells.
Pericycle:
9. Inner to the endodermis
10. Present parenchymatous pericycle
11. Some places present sclerenchyma cells.
Vascular System:
12. Vascular bundles are present in three rings.
 Innermost ring are present two large
bundles
 Middle ring the number ranges from 6 to 14
 Outermost ring consists of 15 to 20
vascular bundles.
13. Vascular bundles of innermost and middle
rings are medullary bundles.
14. Conjoint, collateral and endarch.
15. Two vascular bundles of the innermost ring arc
large, oval and lie opposite to each other with
their xylem facing towards centre and phloem
outwards.
16. Inner and middle rings may show a little
secondary growth.
17. Phloem consists of sieve tubes, companion cells and phloem parenchyma
18. Xylem consists of vessels, tracheids and xylem parenchyma.
19. Outermost ring of the vascular bundles contain inter-fascicular cambium
20. Inter-facicular cambium is absent in other two rings.
21. Cambium develops secondarily from the pericycle and becomes active.
22. It cuts secondary phloem towards outer side and secondary xylem towards inner side.
23. The primary phloem present next to pericycle.
24. Primary xylem is situated near the pith.
25. Interfascicular cambium also soon becomes active and cuts internally the row of cells which become
thick walled and lignified and are known as conjunctive tissue.
Pith:
26. It is well developed,
27. Parenchymatous and present in the centre.
Figure: Anomalous secondary growth in
Boerhaavia stem

25. Anomalous secondary growth in Dracaena stem
Epidermis
1. The outer most, single layerd, parenchyatous cells
Hypodermis
2. Situated blow the epidermis
3. composed of sclerenchymatous cells
Ground tissue
4. Undifferentiated parenchymatous cells
Vascular bundles
5. Closed type, scattered in the ground tissue, xylem is endarch
6. The secondary thickening is initiated by the
formation of special meristematic zone in the
innter cortical region
7. Multilayered cambial ring is differentiated from
the inner cortical cells
8. Lying outside the vascular bundles
9. The shape of cambial cells varies and activities
are abnormal
10. Large number of cells to the inner side and few of
outside
11. The cells produced external to the cambium are
parenchymatous
12. Inner side is partially parenchymatous and
partially vascular in nature
13. These parenchymatous cells develop into lignified
conjunctive tissue
14. Cambium differentiated into secondary vascular
bundles
15. Secondary vascular bundles are concentric-
amphivassal type
16. Consist centrally placed phloem and surrounded
by the xylem
17. Initially divide anticlinal division and these cells
undergo a periclinal division
18. Later division to form a mass of cells
19. Centrally placed cells form phloem cells
20. Peripheral cells differentiated into xylem elements
Figure: Anomalous secondary growth in
Dracaena stem

26. Unit 4
Anatomy of dicot leaf
Epidermis:
1. Present on the upper and lower surfaces.
2. It consist one-celled thick layers of barrel-shaped, compactly arranged cells.
3. Thick cuticle is present on the upper epidermis than lower epidermis.
4. Stomata are present only on the lower epidermis.
Mesophyil:
5. Differentiated into palisade and spongy parenchyma.
Palisade parenchyma
6. Palisade lies just inner to the upper epidermis.
7. It is composed, elongated cells arranged in two layers.
8. The cells of palisade region are compactly arranged and filled with chloroplasts.
9. Palisade cells are arranged at a plane at right angle to the upper epidermis
10. The chloroplasts in them are arranged along their radial walls.
11. Parenchymatous cells are present above and below the large vascular bundles.
Spongy parenchyma
12. Spongy parenchyma region is present just below the palisade
13. It extends upto the lower epidermis
14. The cells of spongy parenchyma are loosely arranged, filled with many chloroplasts
15. They leave big intercellular spaces.
Vascular Region:
16. Many large and small vascular bundles are present.
17. Vascular bundles are conjoint, collateral and closed.
18. Each vascular bundle is surrounded by a bundle sheath.
19. Bundle sheath is parenchymatous
20. Large bundles it extends upto the epidermis with the help of thin-walled parenchymatous cells.
21. The xylem is present towards the upper epidermis
22. Xylem consists of vessels and xylem parenchyma.
23. Protoxylem is present towards upper epidermis
24. Metaxylem is present towards the lower epidermis.
25. Phloem is situated is present towards the lower epidermis
26. Phloem consists of sieve tubes, companion cells and phloem parenchyma
Figure: Transverse section of Dicot Leaf

27. Lateral root formation
 Lateral roots are branches of the tap root
 They are initiated in relatively mature tissues some distance from the apex, often in acropetal sequence
 The most recently-formed lateral roots are usually those nearest to the root apical meristem
 In angiosperms, lateral roots have a deep-seated (endogenous) origin
 Root formation is usually initiated in groups of ‘‘founder cells’’ in the pericycle, xylem poles
 The position of lateral root initiation in the pericycle is usually at a point adjacent to a protoxylem pole
 The root is diarch, initiation is opposite a phloem pole
 In monocots lateral root initiation can be opposite either protoxylem or phloem poles
 The founder cells undergo a series of periclinal and anticlinal divisions to form a lateral root
primordium
 In many species some subsequent cell divisions occur in the endodermis
 Both the pericycle and the endodermis contribute to the tissues of the lateral root
 The growing lateral root pushes its way through the cortex and epidermis of the parent root, either by
mechanical or enzymatic action
 Adventitious roots are formed in other parts of the plant, primarily stem tissue
 They have various sites of origin, from deep-seated (endogenous), to (more rarely) exogenous
 Arise from superficial tissues such as the epidermis (e.g. in surface-rooting Begonia leaves)
 In most monocots adventitious roots arise from cell divisions in the pericyclic region of the stem
 The primary thickening meristem contributes to adventitious root formation
 Adventitious roots are often formed at nodes on the stem, which is why in horticulture cuttings are most
commonly taken from just below a node
 Adventitious roots may also form from callus tissue at the site of a wound.
Figure: Formation of lateral roots

28. Nodal anatomy
 A shoot bears ‘nodes’ and ‘internodes’
 The vascular system of the leaf is in continuation with the vasculature of stem
 This connection is found in the nodal region of stems
 This part the strand from the stem bundles move towards the leaf
 This bundle extending from the base of leaf to the point of its junction with a strand in the stem is termed leaf trace
 Leaf trace is a vascular bundle that connects the vascular system of the leaf with that of the stem
 The leaf trace may thus be described as the cauline part of the vascular supply of the leaf
 At the point in the node form where the leaf trace begins, a region of parenchyma occurs in the vascular cylinder
of stem and is known as leaf gap or lacunae
 The leaf gap is formed due to the origin of leaf trace
 The term lacuna is used in place of gap and the nodes are called
 Unilacunar
 Trilacunar and
 Multilacunar
a) Unilacunar
 The node with a single gap and a single trace to the leaf
b) Trilacunar
 The node with three gaps and three trace to the leaf (one
median and two lateral)
c) Multilacunar
 The node with several to many gaps and traces to a leaf
Figure: Cross section of stems with different types of nodal anatomy
Figure: Unilacunar and Trilacunar node

29. Unit 5
Microtechniques
 Microtechnique is an aggregate of methods used to prepare micro-objects for studying.
 It is currently being employed in many fields in life science.
 Two well-known branches of microtechnique are
(i) Botanical (plant) microtechnique and
(ii) Zoological (animal) microtechnique.
E. Fixation of plant materials
 Fixation is the preservation of biological tissues from decay
 Decay due to autolysis or putrefaction
 It terminates biochemical reactions
 Increase the treated tissues' mechanical strength or stability
 Tissue fixation is a critical step in the preparation of histological sections
 Its broad objective being to preserve cells and tissue components
 To allow for the preparation of thin, stained sections
 Allows the investigation of the tissues' structure, shapes and sizes of such macromolecules
(proteins and nucleic acids)
F. Sectioning
 Sections are known as thin slices
 It needs to be tested cellular structures
 This technique used for the preparation of tissue of animals and plants
 For using under optical microscopy, the thickness of the material should be between above 2 and 25
micrometers
 Observing under electron microscopy, sections should be from 20 to 30 nanometers
 Microtome used in sectioning of sufficiently thin slices
 Objects cannot satisfy the requirement of thickness, materials are required to be dehydrated using
alcohol before section
 Three commonly used sectioning method are
(i) Freehand section technique
(ii) Paraffin method, and
(iii)Celloidin method

30. Freehand section
 This method requires simple laboratory supplies
 Freehand slicing is a method of making thin slices of fresh or fixed experimental materials with a hand-
held blade (double-edged razor blades)
 Freehand slicing refers to the method of directly cutting fresh or fixed materials (generally plants with a
low degree of lignification) into thin slices without special instruments or special chemical reagents
G. Staining
 Plant tissues have a color, there is little chromatically difference between plant tissues makes it difficult
to differentiate botanical structure
 Material is usually dyed before installation
 The process is called staining, which can be used to prepare botanical specimens so that it is possible to
distinguish one part of the sample from another in terms of color.
 Proper selection of staining methods can provide specific histochemical information and define cellular
components clearly
 Acid dyes can be used when staining micro slides
 Example, acid dyes are in use when coloring nuclei
 Other cellular components are stained using alkaline
 There are also staining machine used for staining, which allows tissue to be stained automatically
H. Mounting
 Before you start building your slides, make sure you have everything you will need, including slides,
cover slips, droppers or pipets and any chemicals or stains you plan to use.
 Two main types of slides
 Well slides have a small well, or indentation, in the center to hold a drop of water or liquid substance
(glycerol)
(i) Dry Mount
 In a dry mount, the specimen is placed directly on the slide.
 A cover slip may be used to keep the specimen in place and to help protect the objective lens.
 Dry mounts are suitable for specimens such as samples of pollen, hair, feathers or plant materials
(ii) Wet Mount
 In wet mount, a drop of water or glycerol is used to suspend the specimen between the slide and cover
slip
 Place a sample on the slide.

31.  Using a pipette, place a drop of water on the specimen.
 Then place on edge of the cover slip over the sample and carefully lower the cover slip into place using
a toothpick or equivalent.
 This method will help prevent air bubbles from being trapped under the cover slip
(iii) Whole Mount Preparation
 The whole mount method is superior to the sectioning method because the sample is able to be viewed
globally and 3-D reconstruction is possible.