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Department of Botany, DAV College, Jalandhar (PB.)

131

BOTANY

Lab Manual

BSc.-II Medical

Semester IV


132

Syllabus

1. Study of any commonly occurring dicotyledonous plant (Solanum nigrum) to the body

plan, organography and modular type of growth.

2. Study of various Life forms exhibited by flowering plants (by a visit to a forest or a

garden).

3. Study of tree like habit in cycads, bamboo, banana and yucca and comparison with true

trees as exemplified by conifers and dicotyledons.

4. L.S. shoot tip to study the cytohistological zonation and origin of leaf primordia.

5. Monopodial and sympodial types of branching in stems (especially rhizomes).

6. Anatomy of primary and secondary growth in monocots and dicots using free hand razor

technique (Solanum, Boerhavia, Helianthus, Mirabilis, Nyctanthus, Dracaena, and

Maize) hand sections or prepared slides.

7. Structure of secondary xylem and phloem. Growth rings in wood.

8. Microscopic study of wood in T.S, T.L.S, and R.L.S.

9. Field study of diversity in the leaf shape, size, thickness, surface properties.

10. Internal structure of leaf.

11. Structure and development of stomata (using epidermal peel of leaf).

12. Study of anatomy of root. Primary and secondary structure.

13. Examination of a wide range of flowers available in the locality and methods of their

pollination.

14. Structure of anther, microsporogenesis (using slides) and pollen grains (using whole

mounts).

15. Pollen viability using in vitro pollen germination.

16. Structure of ovule and embryo sac development from permanent slides.

17. Nuclear and cellular endosperm. Embryo development in monocots and dicots (using

permanent slides/dissection).

18. Simple experiments to show vegetative propagation (leaf cuttings in bryophyllum,

begonia; stem cuttings in rose, money plant, sugarcane and bougainvillea).

19. Germination of dormant and non dormant seeds.


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1. Study of any commonly occurring dicotyledonous plant (solanum nigrum) to the body

plan, organography and modular type of growth.

A typical dicotyledonous plant chiefly consist of 2

parts-

• Root system-Root and its branches together

constitute branch system typically underground

and have 1, 2, 3 roots and rootlets. The root is

formed from radical. There are 2 types of root

system. Tap root system found in dicot usually

and adventitious root system found in monocot.

In tap root system main root arise from radical

and grows throughout the life as the main root.

Secondary and tertiary branches arise on main

root. Chief function of root is to anchor the

plant to soil, absorbs water and minerals and

hold soil particles.

• Shoot system-it is above ground part of plant.

Shoot is truely phototropic and transport food

from leaves to all part of plant. It bears leaves,

flowers, fruits etc.

Leaves-leaves are green,flat,expanded, lateral

growth of stem or its branches. It has

lamina,petiole and stalk. It helps in

photosynthesis, respiration and transpiration.

Flower- a flower is modified condensed shoot

usually brightly coloured. In Solanum nigrum

flowers are inconspicuous white form on

monochisally cyme called rhipidium having

flower in same plane. Flowers are typical

solanacious type having 5 sepals, 5 petals, five

stamens and two fused carpels. Corolla is star

shaped called rotate type.

Fruits- fruits in solanum are small purple to

orange colour berries. Berry encloses seed

which contain embryo and reserve food

material.


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Modular part of growth

In angiosperms, there are 4 types of meristems

i.e; apical, intercalary, lateral and diffused.

These meristems are responsible for size, shape,

complexity of plant. The modular growth is

basically dependent on three structural units: -

cell-metamer-module.

• Modular growth in shoot system- shoot apex consists of meristematic

zone of dividing cells. It is associated

with quadnating and repeating sets of

nodes and internodes. A single set of

node, internode and bud is known as

metamer. Metamer together constitute

module.

• Modular growth in root system- root

system, have primary root and lateral

branches. These branches arise in a

definite pattern from root apex. Primary

root and its branches are all modules

from which root system is constructed.

Apical dominance of main root

influences the appearance of laterals.


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1. Study of various Life forms exhibited by flowering plants (by a visit to a forest or a

garden).

Hydrophytes

Plants growing in water or in habitat rich in water are known as hydrophytes. They are classified

into three main groups.

1. Free-floating hydrophytes: these are plants float freely on the water surface, e.g.

Eichhornia, Salvinia.

2. Submerged rooted hydrophytes: these plants remain below the water surface but are

attached to the bottom by their roots, e.g., Hydrilla, Vallisneria.

3. Rooted with floating leaves: these plants are attached to the bottom by their roots but

their leaves float on the water surface, e.g. Nelumbo, Marsilea, etc.

Characteristics features of hydrophytes-

• Root system is reduced in free-floating plants and even absent in some submerged plants.

However, it is well developed in rooted hydrophytes.

• Root pockets develop in free- floating hydrophytes like Azolla.

• Their stems are spongy, delicate and flexible.

• Leaf petioles are long in rooted with floating leaves hydrophytes like Nymphaea.

• Leaves of submerged plants are dissected to reduce the water resistance, e.g., Hydrilla,

Vallisneria. Floating leaves have waxy surface and water does not adhere to them.

• Cuticle is absent in various plant parts.

• Root and stem contain large air chambers that provide buoyancy.

• Mechanical tissue such as xylem is poorly developed or reduced.

• Stomata are absent in submerged leaves and present only on the upper surface of floating

leaves.

The best life forms of plant are based on water availability in the habitat. Accordingly

following three major groups of plants are recognized.

Hydrophytes- plants growing in water or in habitat rich in water.

Xerophytes- plants growing in habitats where available is practically negligible.

Mesophytes- plants growing in habitats where available water is moderately sufficient.


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Plants growing in hot and dry conditions are known as xerophytes. These are two main groups of

such plants.

(i) Succulent Xerophytes.

(ii) Non-succulent xerophytes.

Characteristic feature of succulent xerophytes:

• These plants posses fleshy and stunted stem.

• Their cells contain large quantity of mucilage.

• They can store water in this tissue during the brief rainy season.

• The stem becomes thick green leaf-like structure to perform photosynthesis.

• Their leaves are small, deciduous or modified into spines to cut the rate of water loss

through transpiration.

• They posses shallow root system spreading horizontally.

• Epidermal cells of their leaves and stems are thick and highly cuticularized.

• Their stomata remain closed during hot days and open at night.


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Characteristic features of non-succulent xerophytes:

• Their root system is well developed and fast growing.

• Their taproot system grows deep into the soil and reaches the water table.

• Their stem is generally hard and woody, covered with wax, silica, hair, etc.

• Their leaves are reduced or modified to cut the rate of water loss.

• Epidermal cells of the leaves are thick walled.

• The number of stomata per unit area is very less.

• Stomata are mostly sunken.

• The amount of mechanical tissue is higher.

• Presence of double or multiple epidermises to reduce transpiration.

Acacia sp Calotropis procera


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MESOPHYES are those terrestrial plants which grow in moderately moist habitats and need

well-aerated soils. Broad-leaved trees growing in wet depressions, along lakes and rivers, are

mesophytes. They stand between hydrophytes and xerophytes and lack specific adaptations of

them. Some of the significant morpho-anatomical features of mesophytes are as follows:

1. Root system is well developed. Roots are fairly branched and contain root caps and root-

hairs.

2. Stems are generally aerial, solid and fairly branched.

3. Leaves are generally large, broad, and thin and varied in shapes. They are green and lack

hairy or waxy coatings.

4. In all aerial parts, cuticle is moderately developed.

5. Epidermis is well developed and has no chloroplasts.

6. Stomata generally present on both the surfaces of leaves.

7. Mesophyll in leaves is differentiated into palisade and spongy parenchyma, with many

intercellular spaces.

8. Well developed vascular and mechanical tissues are well differentiated.

9. Mesophytes may exhibit temporary wilting during noon hours.

Examples: Grass, Corn, Clover, Field crops, Goldenrod.


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3. Study of tree like habit in cycads, bamboos, banana, and yucca and their comparison

with true trees as exemplified by conifers and dicotyledons.

Tree like habit in cycads

• Cycads look like a small tree.

• The stem is woody and hard enough but dwarf.

• Plant is symmetrical which supports a crown of

shiny dark leaves.

• Leaves are deep, semiglossy green about 50 to 150

cm long.

• Leaflets are long, strongly recuured with spiny

edges. The petiole has small protective barbs.

• Cycas posses apogeotropic branches of the lateral

roots, which are thick, blue, and repeatedly

branched. These coralloid roots posses anabaena in

them and do not show secondary growth.

• Plant is dioecious with separate male and female

plants.

• The microsporophylls are arranged in a compact

spiral around the woody central axis of male cone.

• The microsporophyll is woody, flattened wedge

shaped.

• The fertile part of microsporophyll bears numerous

microspores (pollen grains).

• The megasporophylls arise in spiral arrangement

towards the apex of female tree.

• Each megasporophyll is an orange-brown structure

and consists of a lower fertile portion bearing 1-3

pairs of ovules laterally.

• The whole megasporophyll is densely covered with

brown wooly hairs.

• The ovule is orange red; erect structure consisting of

mass of parenchyma called nucellus, covered by a

single integument differentiated into fleshy, middle

stony and inner fleshy layers.

• The internal structure of root, stem and leaf resembles

with the dicot trees.


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Tree like habit in banana

• The banana plant is largest herbaceous

flowering plant.

• Banana has a stout central axis (false stem)

which grows up to a height of 10-15 feet.

• The stem is formed by the stiff sheathing

petioles which are rolled round one another.

• The true stem grows through the sheath and

forms the large compound spadix.

• In banana, the formation of inflorescence marks

the end of its growth.

• When the parent plant dies, the underground

suckers get separated and grow into new plants.

• The stem in banana is underground rhizome; the

aerial psuedoaerial stem (shaft) is composed of

long stiff leaf sheaths rolled round each other

due to which the plant of banana gives tree like

appearance.

• The leafs in banana are radical, simple, large,

petiole, alternate and have unicostate parallel

venation.

• Inflorescence in banana is represented by

compound spadix, covered with large violet pink

coloured bracts called spathe. The male flowers are

arranged towards the apex and the female towards

the base of spadix.

• The whole plant of banana represents a tree like

habit.


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Tree like habit in yucca

• The yucca plant possesses hard tree like

structures. It is a genus of perennial shrubs and

trees in agave family.

• The roots are deep feeders and much branched.

The internal structure of roots resembles in the

tree growing in dry areas.

• Stem in yucca is aerial but woody; most of the

part is underground and is rhizome.

• Yucca stem shows anomalous secondary growth

which is an exception in monocots and takes

place by centrifugal formation of the central

vascular bundles and ground tissue as in the

higher woody trees.

• The leaves are long, fleshy and dull green in

colour. The internal structure resembles with

xerophytic leaf.

• The flowers are large and present in Panicles.

• The stem is branched and undergoes profuse

secondary growth.

• Flowers are bell-shaped and posses typical

liliaceous characters.


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TREE LIKE HABIT IN BAMBOO (bambusa)

• Bamboos are grasses in origin but they attain

tree like habit.

• The main stem of bambino is called Culm. It is

the made up of jointed segment called nodes

and internodes.

• Nodes of bamboo are always solid and

internodes are usually hollow.

• Bamboo has underground stems called

rhizomes which transport water, nutrients and

anchor the plant to soil.

• Roots are adventitious fibrous roots which are

usually present in bunches.

• The branches of bamboo determinate into

foliage leaves. The green part of leaf is called

blade and lower part of leaf is sheathing leaf

base. This encloses and protects the newest

leaf emerging from growing tip.

• At the joint of leaf blade and sheath a

membranous ligule is present. It has clasppimg

ends called auriclets.

• The seeds of bamboo may be present at the

height of 80-100 feet and used for food of

other angiosperms or eaten by people.

The secondary growth in stem is very fast as

compare to other angiosperm and

gymnosperm.


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4. L.S. shoot tip to study the cytohistological zonation and origin of leaf primordia.

Apical meristems are located at the tips of stems and at the tips of roots just behind the root cap.

The plant tissues that result from primary growth are called primary tissues. During periods of

growth, the cells of apical meristems divide and continually add more cells to the tips of a

seedling’s body. Thus, the seedling lengthens. Primary growth in plants is brought about by the

apical meristems. The elongation of the root and stem forms what is known as the primary plant

body, which is made up of primary tissues. The primary plant body comprises the young, soft

shoots and roots of a tree or shrub, or the entire plant body in some herbaceous plants. Both root

and shoot apical meristems are composed of delicate cells that need protection. The root apical

meristem is protected from the time it emerges by the root cap. Root cap cells are produced by

the root meristem and are sloughed off and replaced as the root moves through the soil. A variety

of adaptive mechanisms protect shoot apical meristem during germination (figure 38.4). The

epicotyl or hypocotyl (“stemlike” tissue above or below the cotyledons) may bend as the

seedling emerges to minimize the force on the shoot tip. In the monocots (a late evolving group

of angiosperms) there is often a coleoptile (sheath of tissue) that forms a protective tube around

the emerging shoot. Later in development, the leaf primordia cover the shoot apical meristem

which is particularly susceptible to desiccation. The apical meristem gives rise to three types of

embryonic tissue systems called primary meristems. Cell division continues in these partly

differentiated tissues as they develop into the primary tissues of the plant body. The three

primary meristems are the protoderm, which forms the epidermis; the procambium, which

produces primary vascular tissues (primary xylem and primary phloem); and the ground

meristem, which differentiates further into ground tissue, which is composed of parenchyma

cells. In some plants, such as horsetails and corn, intercalary meristems arise in stem internodes,

adding to the internode lengths. If you walk through a corn field (when the corn is about knee

high) on a quiet summer night, you may hear a soft popping sound. This is caused by the rapid

growth of intercalary meristems. The amount of stem elongation that occurs in a very short time

is quite surprising.


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L.S of shoot tip


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5. To study monopodial and sympodial types of branching in stems (especially

rhizomes)

Theory- Rhizome

• Rhizome is usually an organ of perennation as

well as vegetative propagation.

• It bears leaves, buds & adventitious roots.

• The leaves may be scale like (small &

thin,whitish or brownish in colour)

• Rhizome bears distinct nodes and internodes.

• From the nodes arise aerial, erect branches.

• The rhizome may be monopodial when it has

one main axis.

• It may be sympodial when many axes are

fused with one another.

• The stem of mentha (mint) is the example of

monopodial shizome.

• The stem or Iris and ginger represent the

sympodial rhizome.

Monopodial branching- here the terminal

bud continues its activity indefinitely giving

rise to a straight unbranched single stem axis.

The lateral branches arise from axillary buds.

Since in this type of growth, there is a single

main axis for the shoot it is called monopodial.

Monopodial branching is found in mint.

Sympodial branching-here the apical bud

after forming a small part of the axis stops

its activity. Further growth of axis occurs

from axillary bud. The main axis is formed

by the fusion of bases of axillary branches

and the main stem; it is called sympdial

axis or sympodium. It is found in case of

ginger, turmeric, canna, saccharum etc.

Department of Botany, DAV College, Jalandhar (

6. Anatomy of primary and secondary growth in monocots and dicots using free hand

razor technique (Solanum

and Maize) hand sections or prepared slides.

Study of primary growth in a dicot

Anomalous structures

Study of anatomy of Nyctanthus arbortristis

1. Epidermis -consists of parenchymatous cells ,

layered, compctly arranged, interrupted by multicellular

hair ,which is the extension of the epidermal cells , it is

covered above by the layer of cuticle, stomata are also

prsent at intervals.

2. Cortex – this region is divisible into three distinc

parts

(a) Hypodermis- situsted below the epidermis,

consist of 4 to 5 layers of collenchyma.

(b) Cortex- consisting of large rounded, oval, thin,

walled intercellular spaces situated below the

hypodermis. Some isolated resin ducts are also

present in the general cortex.

(c) Endodermis- innermost layer or cortex having

barrel-shaped cells. Endodermis is single layered

having barrel shaped cells without casparian

strips. Cells are composed of single layered

parenchyma.

3. Pericycle is heterogenous having both

sclerenchymatous and parenchymatous cells.

Sclerenchymatous patch is present opposite to vascular

bundles and parenchymatous patch is present in between

the two vascular bundles and performs the storage

function.

4. Vascular bundles are present in the form of a ri

and called as the eustele, the bundles are conjoint,

collateral, endarch and open having well developed pith

on the inner side.

5. Pith cells are parenchymatous and are having storage

function.

College, Jalandhar (PB.)

Anatomy of primary and secondary growth in monocots and dicots using free hand

Solanum, Boerhaavia, Helianthus, Mirabilis, Nyctanthus

and Maize) hand sections or prepared slides.

Study of primary growth in a dicot stem (T.S stem of Helianthus)

Study of anatomy of Nyctanthus arbortristis

consists of parenchymatous cells , single

layered, compctly arranged, interrupted by multicellular

hair ,which is the extension of the epidermal cells , it is

covered above by the layer of cuticle, stomata are also

this region is divisible into three distinct

situsted below the epidermis,

consist of 4 to 5 layers of collenchyma.

consisting of large rounded, oval, thin,

walled intercellular spaces situated below the

hypodermis. Some isolated resin ducts are also

cortex.

innermost layer or cortex having

shaped cells. Endodermis is single layered

having barrel shaped cells without casparian

strips. Cells are composed of single layered

is heterogenous having both

hymatous and parenchymatous cells.

Sclerenchymatous patch is present opposite to vascular

bundles and parenchymatous patch is present in between

the two vascular bundles and performs the storage

are present in the form of a ring

and called as the eustele, the bundles are conjoint,

collateral, endarch and open having well developed pith

cells are parenchymatous and are having storage

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Anatomy of primary and secondary growth in monocots and dicots using free hand

Nyctanthus, Dracaena


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To study the anatomy of primary growth in monocot stem (T.S. stem of maize)

To study the anatomy of Mirabilis jalapa

Epidermis

It is an outermost single layer of rectangular cells.

The cells of the epidermis are thickly cuticularised.

A few are present which lead into a sub-stomatal cavity

below

Ground tissue

All the tissues inside the epidermis form ground tissue.

It covers most of the section.

A few celled deep sclerenchymatous zones occur just

below the epidermis. It is interrupted at regular intervals

by patches of chlorenchyma.

The patches of chlorenchyma are bounded by

sclerenchyma on their sides and lower faces.

The stomata open only in thin walled parenchyma with

many intercellular spaces.

Vascular tissue system

Vascular tissue system is represented by numerous

vascular bundles.These are arranged in two series.

The bundles of the peripheral series are smaller than the

bundles of the inner series.

The bundles of the peripheral series are mostly

embedded in the sclerenchymatous patch situated below

the epidermis.

Vascular bundles are conjoint,collateral,endarch &

closed.

Each vascular bundles is almost completely enclosed by

a band of sclerenchyma.Bundle sheath is prominent at

the upper and the lower extremities of the vascular

bundle.

The xylem elements are arranged in almost Y-shaped

organisation which occupies the lower region of the

vascular bundle.

Metxylem elements are large and the smaller

protoxylem elements are situated near the inner face of

the vascular bundle

The phloem occurs in the peripheral region of the

bundle. It consists of sieve tubes and companion cells.

There is a hollow cylinder in the centre of the axis.


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Internal structure of Stem of Boerhaavia diffusa

1. In transverse section, the stem shows a wavy outline.

Outermost layer is epidermis composed of single

layered compactly arranged parenchymatous cells with

no intercellular spaces. Many epidermal cells bear

multicellular hair, which are not the outgrowth of

epidermal cells.

2. Next to epidermis is cortex which is differentiated

into two zones, next to epidermis is collenchymatous

cells, next to collenchyma cells lies the zone of

chlorenchyma cells. It is made up of 4-6 layers of cells.

The are circular, oval or even polygonal and have

abundant chloroplasts.

3. Innermost layer of cortex constitutes the

endodermis. It is clearly distinguishable. It is made up

of thick walled tubular cells with no intercellular

spaces.

4. Next to endodermis lies the zone of parenchymatous

cells of pericycle which are interrupted with

sclerenchymatous cells in between in the form of

patches.

5. Vascular bundles are present in three rings. The

outermost ring have 15-20 small bundles, this ring

surrounds a middle ring of 6-14 vascular bundles.

These are smaller in size and oval or rounded in shape.

In the innermost ring are present two larger vascular

bundles which lie in pith, these are called das

medullary bundles. Of all the bundles these are the

largest in size and are oval in shape. These bundles are

fully developed. The central bundles are enveloped in a

thin walled sheath and lie opposite to each other with

xylem facing towards the center and phloem facing

outwards. The vascular bundles are conjoint, collateral,

endarch and open.


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Internal structure of stem of Mirabilis jalapa

1. Epidermis is made up of single layered

compactly arranged parenchymatous cells with no

intercellular spaces. Cells are thin walled, covered

with a layer of cuticle on the outer side.

2. Cortex is differentiated to two zones. Below the

epidermis is present a zone of collenchymatous

cortex, this occurs in the form of patches,It

constitutes 2-4 layers of cells which are thickened at

the corners. Next zone is made up of chlorenchyma

cells. This constitutes few layers of loosely arranged

oval or spherical cells. They are rich in chloroplast

content and enclose the small intercellular spaces.

3. Innermost layer of cortex is composed of colorless

parenchymatous cells rich in starch content which is

called as endodermis.

4. Next to endodermis is present one to two layers of

thin walled parenchymatous cells which composes

pericycle tissue.

5. Large number of scattered bundles are visible in

the pith region known as medullary bundles. Of

these only two are larger while others are smaller

and are scattered. In addition there is a normal ring

of vascular bundles next to the pith. There are

incomplete dwarf bundles in the outer ring, these

contain only phloem.

6. The bundles in the outer ring are complete. They

are conjoint, collateral, endarch and open.

7. Medullary bundles are larger and are developed

earlier as compared to other bundles which are

smaller in size.


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Internal structure of stem of Nyctanthes arbor-tristis

The stem of this plant has prominent angles and reveals a

quadrangular outline in a transverse section.

1. Epidermis is single layered parenchymatous with a

compact arrangement. The cells are covered by a

continuous layer of thick cuticle. Multicellular hair

arises from the epidermal tissue.

2. Cortex is followed by epidermis having a few

layered collenchymatous tissue towards outside and

oval, rounded cells on the inner side. The main function

of cortex is storage.

3. Endodermis and pericycle are not distinct.

4. Normal vascular bundles occur in the center in the

form of a ring, the bundles are conjoint, collateral,

endarch and open, in addition to the normal ring of

vascular bundles there is present four inversely oriented

vascular bundles in the cortex region at the four corners

of the stem.

5. These cortical bundles always get restricted to the

four prominent angles of the stem. The phloem in such

bundles is restricted towards the inner side and xylem

towards the outer side. The bundles have the exarch

condition.

6. The cambium present in the cortical bundles adds a

small amount of secondary vascular tissue sin a normal

manner.

7. The cambium in normal ring in the center also

functions in a normal manner and produces secondary

phloem towards outer side and secondary xylem

towards inner side.

8. Pith- In the center of the stem there is broad pith

which is composed of thin walled cells.


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Internal structure of stem of Dracaena

Dracaena is a monocot and as the vascular bundles

are closed, the secondary growth does not occur in

monocots, secondary growth in dracaena is regarded

as anomalous.

1. The outermost layer of the stem constitutes

epidermis which is made up of rectangular

cells. On the outerside it is covered with a

layer of cuticle.

2. Following the epidermis is found a layer of

sclerenchymatous hypodermis. The cells of

the ground tissue may or may not enclose


3. Numerous vascular tissues lie scattered in

the ground tissue. These are arranged in the

form of rings. The bundles in the outer ring

are smaller and more in number as compared

to the inner rings.

4. Each vascular bundle is surrounded by a

sclerenchymatous bundle sheath. The sheath

is more prominent towards the outerside.

5. Xylem elements are arranged in the form of

letter ‘v’. The metaxylem elements occupy

the arms of ‘v’ and protoxylem elements are

present at the angle of ‘v’.

6. Small amount of phloem lies between the

metaxylem elements, lysogenous cavity is

absent.


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154

7. Structure of secondary xylem and phloem.

XYLEM

Xylem tissue functions in both water transport and mechanical support. In non-angiosperm

tracheophytes, tracheids serve both purposes; in most angiosperms, the xylem contains both

vessel elements, which have a larger diameter and are specialized for water transport, and fibers

for mechanical strength.

Xylem cells commonly have cell walls impregnated with lignin and reinforced with spiral or

ring-like thickenings that project into the lumen of the cell. Both features reinforce the cells for

mechanical support.

Xylem cells are dead and empty of cell contents at maturity and essentially form tubes for water

transport. However, plants have no pumps to move water through these hollow tubes. Thus water

molecules are pulled in long, hydrogen-bonded chains from rhizome to leaf. If the chain breaks,

for example if a bubble forms in a xylem cell, the involved cells lose their function and cannot be

repaired. Since xylem can be modeled as physical pipes following hydrodynamic principles, the

water-transport ability of ancient plants can be easily calculated. Parenchyma cells are often

present in xylem tissue, where they help maintain water balance and carry out metabolism within

the tissue. Because more than one cell type is present in xylem, it is called a complex tissue.

Fibres and fibre-tracheids- FIBRE is defined as ‘a general term of convenience in wood

anatomy for any long, narrow cell of wood or bast other than vessels sieve tubes and

parenchyma. Note: often further qualified as wood fibres or bast fibres; the former including

both the tracheids of gymnosperms (softwoods) and the libriform wood fibres and fibre-tracheids

of woody angiosperms (hardwoods). Also used loosely for wood elements in general’.


155

Types of fibres are;

1. LIBRIFORM FIBRE: an elongated, commonly thick-walled cell with simple pits, usually

distinctly longer than the cambial initial as inferred from the length of the vessel

members and parenchyma strand’s, e.g. in Baikiaea plurijuga (Rhodesian

teak), Erythrophleum spp. (missanda), Oxandra lanceolata.(lancewood).

2. FIBRE-TRACHEID: this is defined as a ‘fibre like tracheid, commonly thick-walled with

a small lumen, pointed ends, and bordered pit pairs having lenticular to slit-like apertures.

This term is applicable to the latewood tracheids of gymnosperms as well as to the fibre-

like tracheids of woody angiosperms.

It is not always easy to distinguish between fibre-tracheids and libriform fibres,

especially where the pit border is much reduced.

Fibre tracheids are commonly found in Fagus sylvatica (beech), Juglans regia (walnut),

and Dipterocarpus spp. (gurjun).

Both libriform fibre and fibre-tracheids may be:-

a. SEPTATE: A septate fibre is a fibre with thin transverse walls across the lumen,

e.g. in most genera of the Meliaceae and Aucoumea klaineana(gaboon). In these

elements the protoplast divides after the formation of the secondary wall, with the

result that the septa do not include a middle lamella.

b. GELATINOUS: A gelatinous fibre is a fibre having a more or less unlignified

inner wall with a gelatinous appearance - usually characteristic of tension wood.


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Tracheids

A tracheid is a wood cell without perforations (of the kind found in vessels) and with bordered

pits.

Types of tracheids found in hardwoods include:-

• VASCULAR TRACHEID: a cell resembling in form and position a small vessel

member, but without perforations e.g. Ulmus spp. (elms) and Rhamnus

cathartica (buckthorn).


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• VASICENTRIC TRACHEID: a short, irregularly-formed tracheid in the immediate

proximity of a vessel and not forming part of a definite axial row, e.g. commonly found

in Quercus spp. (oaks), Castanea sativa (sweet chestnut). Eucalyptus spp.

and Calophyllum spp. (bitangor).


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PHLOEM

Phloem tissue transports photosynthetic products, other organic molecules (e.g., plant hormones

and waste products), and soluble nutrients throughout the plant. Unlike xylem, phloem is alive at

maturity, but usually with a much reduced cell contents and no nucleus. This is logical because

movement of material through phloem tissue relies on solute gradients and some active transport

that require the activity of living cells. In non-angiosperm seed plants phloem elements consist

mostly of sieve cells (Figure 1.3), while angiosperms have sieve tube cells in association with

parenchymatous companion cells. Phloem fibers also provide some mechanical support. Phloem

cells are commonly unlignified so they do not preserve as readily as xylem.

Growth rings in wood.

Wood is secondary xylem produced by growth of the vascular cambium tissue. At the very

center is the pith. In some trees, this is much softer and possibly a different color than the

surrounding heartwood. Heartwood is made up of dead cells that no longer serve any purpose

except to support the tree. Next is the sapwood, which carries water, minerals, and plant sugars

between the roots and the leaves. This is often lighter in color than the heartwood. Outside the

sapwood, close to the surface, is the cambium, a thin layer of living cells. These cells


159

manufacture the wood as they grow. The cambium is covered by a protective layer of bark. The

cambium grows rapidly at the beginning of each growing season, creating light

colored springwood. As the climate warms, it slows down and produces darker summerwood.

This later growth is somewhat denser and harder than the early springwood. As the weather turns

cold, the cambium becomes dormant until the next spring. This cycle produces

distinctive growth rings. The number of annual rings corresponds to the age of plant.

Dendrochronology is the branch of anatomy which deals with determining the age of plant.

Growth rings vary in width as a result of differing climatic conditions; in temperate climates, a

ring is equivalent to one year's growth. Certain conducting cells form rays that carry water and

dissolved substances radially across the xylem. Bark comprises the tissues outside the vascular

cambium, including secondary phloem (which transports food made in the leaves to the rest of

the tree), cork-producing cells (cork cambium), and cork cells. The outer bark, composed of dead

tissue, protects the inner region from injury, disease, and desiccation.

Cross section of a tree trunk.


160

8. Microscopic study of wood in T.S, T.L.S, and R.L.S.

The tangential section is the section cut through stem longitudinally without passing from

centre.

Observations-

• Tracheids, vessels and medullary rays are seen in this section.

• The bordered pits on tracheary elements are cut and show over-arching borders forming a

dome-like structure. It encloses a small disc in centre called torus.

• The tracheids and vessels are also seen. The tracheids are narrow elements with intact

walls without perforation. The vessels are very broad with perforated end walls.

• Medullary rays are multiseriate, means very thick celled.


161

The radial longitudinal section is obtained by cutting stem in such away so that the

longitudinal cut pass through centre. (RLS)

Observations-

• It shows the presence of secondary xylem consisting of tracheids, vessels and medullary

rays.

• Tracheids are narrow with closed end walls but the radial walls show bordered pits.

• Bordered pits are circular as surrounded by special cellulose thickenings.

• Vessels are distinguishable from tracheids being broader and perforated end walls.

• Medullary rays are multiserate made up of ray tracheids and ray parenchyma.

• Ray tracheids are present on both sides of medullary ray cells.

• The cells of the remaining tissue of xylem are called ray parenchyma which is thin, broad

and mostly living.


Portions of pinewood sections: (1) cross section, (2) radial section, (3) tangential section

(a) edge ot annual ring, (b) summerwood, (c) Springwood, (d) new series of tracheids, (e)

heterogeneous medullary ray composed of ray

tracheids (f) with small bordered pits, and (g) composed ofparenchyma cells with large

windowlike pits, (h) resin canal (epithelial cells lining it clearly visible), (i) cells of parenchyma

surroundi-ng resin canal, (j)bordered pits, (k) medullary ray with horizo




heterogeneous medullary ray composed of ray

(f) with small bordered pits, and (g) composed ofparenchyma cells with large


ng resin canal, (j)bordered pits, (k) medullary ray with horizontal resin canal.

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(f) with small bordered pits, and (g) composed ofparenchyma cells with large


ntal resin canal.


163

9. Field study of diversity in the leaf shape, size, thickness, surface properties.

Morphology of leaf


164


165

VENATION-


166


167

Types of leaf-


168


169


170



171


172

10. Internal structure of leaf.

Internal structure of leaf of Mangifera indica

Epidermis-

• Lower and upper epidermis is single layered.

• The cells are barrel-shaped and compactly arranged.

• Upper epidermis has a thick cuticle and lacks stomata.

• Lower epidermis has thin cuticle and stomata are present.

Mesophyll-

• It is differentiated into spongy and palisade parenchyma.

• Palisade occurs below upper epidermis in two layers, with parenchyma near the larger

vascular bundle. The cells are compactly arranged, long and tubular and chloroplasts are

present.

• Spongy parenchyma forms rest of the tissue. The cells are small, varied in shapes and sizes,

loosely arranged and enclose small air spaces.

• A few air spaces lead to the stomata openings which form sub-stomatal cavity. Numerous

chloroplasts are present near the walls.

Vascular tissue-

• It consists of one large vascular bundle in the midrib and numerous small vascular bundles in

the wings.

• Each bundle is conjoint, collateral and closed and surrounded by a parenchymatous bundle

sheath. Larger vascular bundle has an extensive bundle sheath that extends both toward

lower and upper epidermis.

• Metaxylem is situated towards the lower epidermis and protoxylem towards the upper

epidermis.

• Phloem of the vascular bundle is directed towards lower epidermis.


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T.S of leaf of Nerium (xerophytic leaf)

• In transverse section, the leaf of Nerium shows multilayered upper and lower epidermis. The

outer layers of epidermis consist of thick walled cells and covered externally by thick cuticle.

The lower two layers can be regarded as hypodermis.

• Stomata is present only on the lower epidermis .these cavities also bear multicellular hairs or

trichomes which protect the stomata.

• Mesophyll is differentiated into multilayered palisade and spongy parenchyma.

• The vascular bundle of midrib region is larger in comparison to the vascular bundle of the

wings. They are collateral and closed with xylem towards upper epidermis and phloem

towards lower epidermis. Each vascular bundle is surrounded by parenchymatous sheath.

•


Study of internal structure of monocot leaf

(isobilateral leaf)

Epidermis-Leaf is bounded by lower and upper

epidermal layers.both layers are thickly

cuticularised.Stomata are present in both epidermal

layers.A few large, empty and colourless bullif

cells occur in upper epidermis.

Mesophyll-It is not differentiated into palisade and

spongy parenchyma.it occurs between upper and

lower epidermis.The cells are isodiametricand

containnumerous chloroplasts. These are compactly

arranged and leave only a few intercellular spaces.

Vascular tissue-There are numerous vascular

bundles of variable sizes arranged in a parallel series.

Each bundle is collateral and closed. There is distinct

parenchymatous bundle sheath. The cells of the

sheath posses plastids and starch grains.

A patch of sclerenchyma each is present above and

below the larger vascular bundles and extends up to

the upper and lower epidermal layers respectively.

Large vascular bundles have distinct and more


Study of internal structure of monocot leaf

Leaf is bounded by lower and upper

epidermal layers.both layers are thickly

cuticularised.Stomata are present in both epidermal

layers.A few large, empty and colourless bulliform

It is not differentiated into palisade and

spongy parenchyma.it occurs between upper and

lower epidermis.The cells are isodiametricand

containnumerous chloroplasts. These are compactly

few intercellular spaces.

There are numerous vascular

bundles of variable sizes arranged in a parallel series.

Each bundle is collateral and closed. There is distinct

parenchymatous bundle sheath. The cells of the

d starch grains.

A patch of sclerenchyma each is present above and

below the larger vascular bundles and extends up to

the upper and lower epidermal layers respectively.

Large vascular bundles have distinct and more

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175

11. Structure and development of stomata (using epidermal peel of leaf).

Materials- Leaves of Tagetes, Tridax, Brassica, Ocimum, Tradescantia, cover slips, microscope,

water, safranin, glycerine, needles, forceps etc.

Method-

• Tear the leaf suddenly and with force with lower epidermis upwards.

• A thin membranous lower epidermis gets separated near the broken edges. Pull this

into astrip with forceps or fingers.

• The strip is stained with 1% aqueous safranin, washed in water and then mounted in

glycerine.

Observations-

Stomata- they are the part of epidermal tissue system and present on upper epidermis or lower

epidermis or both surfaces.

Structure- the size of stomata ranges between 7-38um in length and 3-12um in breath. Each

stoma has a pore bounded by two small specialized green nucleated living epidermal cells called

guard cells. The guard cells contain chloroplast, nucleus, mitochondria, vacuoles, starch, ER,

ribosome, microbodies. They are connected with adjacent epidermal cells through

plasmodesmata. Because of their much small size, they are rapidly influenced by turgor changes.

They may be kidney shaped or dumbbell shaped. Kidney shaped guard cells is semilunar like and

thick on inner (concave) side and thin on convex side. In dumbbell shaped, guard cell is linear

dumbell like. Their expanded (bulged) ends are thin walled while the middle part is highly thick

walled.

Types of stomata-

(A) On the basis of the number and orientation of subsidiary cells, 7 types of stomata are

there:-

• Anomocytic type- subsidiary cells absent and the cells surrounding two guard cells are

few and similar to epidermal cells. Eg. Ranunculaceae, Papeveraceae,Nyctaginaceae.

• Anisocytic type-two guard cells of each stoma are surrounded by 3 subsidiary cells (one

is smaller than the other two).eg. Cruciferae, Solanaceae, Umbelliferae.

• Paracytic type- two guard cells of each stoma are surrounded by two or more subsidisry

cells which lie parallel to the guard cells. Eg. Magnoliaceae, Rubiaceae.

• Diacytic type- the two subsidiary cells lie at right angle to the guard cells.eg.

Magnoliaceae, Labiateae, Acanthaceae.

• Actinocytic type- subsidiary cells are 4 or more elongated radially to stoma.


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• Cyclocytic type- subsidiary cells are 4 or more, arranged in a close ring around the

stoma.

• Graminaceous type-in monocots, stomata are dumbell shaped, surrounded by subsidiary

cells lying parallel to the long axis of guard cells.

(B)-On the basis of development of guard cells and subsidiary cells, stomata fall into two

categories-

• Haplochellic type- guard cells are derived from stomatal initial cell but subsidiary cells

are formed by the modifications of adjacent epidermal cells.eg. Tobacco.

• Syndetochellic type- here both guard cells and subsidiary cells are formed from a

common stomatal initial.eg. Sugarcane.


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12. Study of anatomy of root. Primary and secondary structure.

Study of Internal structure of Dicot root

Study of internal structure of monocot root

1. Epiblema is single layered made up of compactly

arranged thin walled parenchymatous cells. Due to the

presence of root hairs it is also called as piliferous

layer. In T.S. cells appears isodiametric, oval or

rectangular. Root hairs are long, tubular, and are

unicellular.

2. Epidermis is followed by cortex which is made up

of thin walled cells; cells may enclose intercellular

spaces for diffusion of gases. Cortical cells may be

replaced by suberised cells as a result of secondary

growth.

3. Cortex is followed by a single layered endodermis

of barrel shaped cells, cells are living and rich in

starch grains, a characteristic band of thickening

known as casparian strip is present along theradial

and tangential cells of the young epidermal cells.

4. pericycle- The layer next to endodermis is

pericycle, it is uniseriate and constitutes outer

boundary of vascular cylinder of the roots. It is made

of thin walled parenchymatous cells.

5. Vascular tissue is present inner to the pericycle.

The root is having alternate and radial arrangement;

primary xylem and phloem appear as separate bundles

with the patches of parenchymatous cells in between

the no. Of xylem and phloem strands vary from 2-4.

6. As the protoxylem elements face towards the

periphery, the root is called as exarch.


Study of Internal structure of

Epidermis

Made up of thin walled parenchymatous cells

arranged without intercellular spaces.

Cortex-shows three sub zones

Exodermis- composed of one to two layers of

thick walled, dead, suberised cells. It helps in

preventing the exit of water from the root tissues.

General cortex- made up of several rows of thin

walled parenchyma showing intercel

The cells of cortex help in the storage of food

material.

Endodermis-Barrel shaped cells arranged

compactly in single layer without leaving any

intercellular spaces. The radial and transverse

walls are wrapped by casparian bands.

Stele-the stele shows three sub zones.

Pericycle-the cells are thin walled,

parenchymatous and compact without


Vascular Tissue-Primary strands of xylem and

phloem are found separately on different radii,

known as “radial” vascular bundles.The xyl

exarch and usually in polyarch condition.

Pith-Made up of thin walled parenchyma, which

primarily helps in the storage of food.


Study of Internal structure of Monocot root

Made up of thin walled parenchymatous cells

arranged without intercellular spaces.

composed of one to two layers of

thick walled, dead, suberised cells. It helps in

preventing the exit of water from the root tissues.

made up of several rows of thin

walled parenchyma showing intercellular spaces.

The cells of cortex help in the storage of food

Barrel shaped cells arranged

compactly in single layer without leaving any

intercellular spaces. The radial and transverse

walls are wrapped by casparian bands.

ele shows three sub zones.

the cells are thin walled,

parenchymatous and compact without

Primary strands of xylem and

phloem are found separately on different radii,

known as “radial” vascular bundles.The xylem is

exarch and usually in polyarch condition.

Made up of thin walled parenchyma, which

primarily helps in the storage of food.

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179

13. Examination of a wide range of flowers available in the locality and methods of their

pollination.

Pollination is the process by which pollen is transferred from the anther (male part) to the

stigma (female part) of the plant, thereby enabling fertilization and reproduction.This takes

place in the angiosperms, the flower bearing plants.A successful angiosperm pollen grain

(gametophyte) containing the male gametes gets transported to the stigma, where it

germinates and its pollen tube grows down the style to the ovary. Its two gametes travel

down the tube to where the gametophyte containing the female gametes are held within the

carpel. One nucleus fuses with the polar bodies to produce the endosperm tissues, and the

other with the ovule to produce the embryo, Hence the term: "double fertilization".The

receptive part of the carpel is called a stigma in the flowers of angiosperms. The receptive

part of the gymnosperm ovule is called the micropyle. Pollination is a necessary step in the

reproduction of flowering plants, resulting in the production of offspring that are genetically

diverse.

Generally pollen grains have a tough protective coat which prevents them from drying up.

Since pollen grains are light, they can be carried by wind or water. Insects visit flowers and

carry away pollen on their bodies. Some of the pollen lands on the stigma of a flower of the

same kind. The transfer of pollen from the anther to the stigma of a flower is

called pollination. If the pollen lands on the stigma of the same flower it is calledself-

pollination. When the pollen of a flower lands on the stigma of another flower of the same

plant, or that of a different plant of the same kind, it is called cross-pollination.

1) Anemophily:

-Wind pollination is called anemophily, and flower is called anemophilous flower, e.g. Monocot

grass, Maize, Jowar etc.

-It is most primitive type of pollination. There is more wastage of pollen grains in anemophily.

Adaptations in anemophilous flowers:


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Flowers are small and inconspicuous.

Flowers are colourless, odourless and nectarless.

Flowers are well exposed on plants.

They produce a large number of dry, light and smooth walled pollen grains.

The anthers are versatile.

Stigma is feathery and branched

Style and stigma is long.


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2) Hydrophily:

-Pollination brought about by water is called hydrophily and flower is called hydrophilous

flower.

- It is found in aquatic plants like Vallisneria, Zostera, Ceratophyllum, Hydrilla etc.

Type of hydrophily:

a)Epihydrophily:

-Pollination takes place on the surface of water,is called epihydrophily.

- Vallisneria is a dioecious plant and pollination occurs on the surface of water.

The male flowers get detached from the' plant and float on the water surface.

Female flowers are produced on long coiled pedicel and projecting above the water surface.

Male flowers come in contact with the stigmas cause pollination.

After pollination long pedicel of female flower coils and brings it back to lower level of water

where the fruit is formed.

b) Hypohydrophily:

Pollination takes place below the water surface is called hypohydrophily. It occurs completely

submerged plants like ceratophyllum and zostera.

Plant bears elongated, needle like pollen grains without exine. pollen grains have the same

specific gravity as that of water. Therefore pollens can float below the surface of water.When

pollens reach the stigma; they coiled around it and germinate.

Adaptations in hydrophilous flower:

Pollen grains are light in weight and covered with wax.

The flowers are inconspicuous.

Flower is without bright colours, fragrance and nectar.

Perianth and other parts of flower are unwettable, and covered by mucilage.

Stigma is long and sticky.

The pollen grains are produced in large number and without exine.

Flowers are generally unisexual.


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3) Entomophily- pollination by insects often occurs on plants that have developed colored petals

and a strong scent to attract insects such as, bees, wasps and occasionally ants (Hymenoptera),

beetles (Coleoptera), moths and butterflies (Lepidoptera), and flies (Diptera). The existence of

insect pollination dates back to the dinosaur era.

Adaptations in entomophilous flower:

Flowers are larger and brightly coloured.

Flowers are more conspicuous.

Smaller flowers are produced in compact groups called inflorescence.

Flowers pollinated by bees are usually blue, purple or yellow. The flowers pollinated by

butterflies are most often red.

Flowers secrete nectar which makes positive attraction to the insects like bees.


183

The pollens of insect pollinating flowers are sticky and spiny (echinulate).

Stigma is short, rough and sticky. In passion flower, staminal tube gives out distinct lobes called

the corona.

Hibiscus rosa-sinensis known colloquially as

Chinese hibiscus

Hummingbirds transfer the pollen from the male

hibiscus to the stigma of the female hibiscus.

Mirabilis jalapa(the 4 o clock flower or marvel

of peru) is the most commonly grown ornamental

species of mirabilis, and is available in a range of

flowers. The flowers are pollinated by long-

tongued moths of the sphingidaefamily, such as

sphinx moths or hawk moths other nocturnal

pollinators attracted by the fragrance of the

flower.

Nerium oleander is an evergreen shrub or small

tree in the dogbane family Apocynaceae. They

are often,but not always, sweet –

scented.Unrewarding flowers cheat insects out of

their customary nectar reward. When the showy

flowers attract scout worker honeybees, but the

workers find no nectar, they return to the hive

and communicate their findings so other bees

don’t waste their time visiting oleander.


184

Salvia officinalis (sage, also called garden sage or common sage) is a member of the family Lamiaceae.

The defining characteristic of the genus Salvia is the unusual pollination mechanism. It consists of

two stamens (instead of the typical four found in other members of the tribe Menthaceae) and the

two thecae on each stamen are separated by an elongate connective. It is the elongation of the

connective that enables the formation of the lever mechanism. When a pollinator probes a male stage

flower for nectar, (pushing the posterior anther theca) the lever causes the stamens to move and

the pollen to be deposited on the pollinator. When the pollinator withdraws from the flower, the lever

returns the stamens to their original position. In older, female stage flowers, the stigma is bent down in a

general location that corresponds to where the pollen was deposited on the pollinator's body. The lever

of most Salvia species is not specialized for a single pollinator, but is generic and selected to be easily

released by many bird and bee pollinators of varying shapes and sizes. The lever arm can be specialized

to be different lengths so that the pollen is deposited on different parts of the pollinator’s body. For

example, if a bee went to one flower and pollen was deposited on the far back of her body, but then it

flew to another flower where the stigma was more forward (anterior), pollination could not take place.


185

Calotropis procera is a species of flowering plant in

the dogbane family Asclepiadaceae. This plant plays

host to a variety of insects and butterflies. Calotropis

is an example of entomophily pollination (pollination

by insects) and pollination is achieved with the help

of bees. In Calotropis, gynostegium is present

(formed by the fusion of stigma and androecium). The

pollen is arranged in a structure named pollinia which

are attached to a glandular, adhesive disc at the

stigmatic angle (Translator Mechanism). These sticky

discs get attached to the legs of visiting bees so that

pollinia are pulled out when the bee moves away.

When such a bee visits another flower, this flower

gets pollinated by the sticky pollinium.


186

4) Ornithophily- Cross pollination which takes place with the help of birds is called

Ornithophily and flowers are called ornithophilous flowers. E.g. Bignonia, Bottle brush, Butea,

Bombax etc.

Adaptations in ornithophilous flower:

Flowers are large and beautifully coloured.

They produce copious mucilaginous nectar.

Flowers are generally scentless.

Some flowers may have edible parts. More commonly the birds with long narrow breaks are

involved in Ornithophily e.g. Humming, Sunbirds, Honey birds, Crow, Bulbul.

The pollen grains are sticky.

Flower produces thick and fleshy floral parts.

Callistemon viminalis, also known as weeping

bottle brush, is a shrub or small tree in the family

myrtaceae. The bright red flower spikes,which are

4-10cm in length and about 3-6 in diameter occur

between spring and summer.Bottlebrush

displays inflorescences composed of many bright

red flowers which are grouped together. The

larger group of flowers make it extremely

attractive to birds, which have good eyesight and

are very sensitive to the colour red. The

infloresences are also found at the apex of

branches, making them more accessible for birds.

Petunia hybrida is one of the best summer flower

belongs to the family solanaceae. The color range

is huge, with varieties available in every color

except orange. The basic petunia is funnel

shaped,but hybridizers have created many

variations including singles and doubles with

petals that have wavy or fringed margins. Bees

are attracted to flowers that have broad petals, so

they can easily alight on the petals. For this

reason, they are less likely to hover near slim-

petaled petunias. Honeybees are attracted to blue

and purple flowers.


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Chiropterophily:

Pollination occurs through a bat is called chiropterophily and flower is called chiropterophilous

flower. It is seen in flowers of Adansonia, Kigellia, Bauhinia, Anthocephalus etc.

Adaptations in chiropterophilous flower:

Flowers open during evening or night.

Flowers are large, dull coloured and have a strong scent like that of rotting fruits.

Flowers produce abundant pollen grains.

Flowers produce copious nectar.

Flowers are tough so that bats can hold on the flowers.

Thevetia peruviana is a poisonous plant.

Thevetia is an evergreen tropical shrub or small

tree. Its large showy and tubular flowers make

an ideal mechanism for birds to visit and reach

for its nectar thereby pollinating the flower.

Kigelia is a genus of flowering plants in the

family Bignoniaceae. . Flowers are produced in

panicles; they are bell-shaped (similar to those of

the African Tulip tree but darker and more

waxy), orange to reddish or purplish green, and

about 10 cm wide. Individual flowers do not

hang down but are oriented horizontally. Some

birds are attracted to these flowers and the strong

stems of each flower make ideal footholds. Their

scent is most notable at night indicating that they

are adapted to pollination by bats, which visit

them for pollen and nectar. They also remain

open by day however, and are freely visited by

many insect pollinators, particularly large species

such as carpenter bees.


188

14. Structure of anther, microsporogenesis (using slides) and pollen grains (using whole

mounts).

Structure of young anther

• The section appears slightly lobed

• The outermost is a single layered epidermis. The cells are cuticularised.

• At four corners of the anther, the derivatives formed as a result of Archesporial cells are

present.

• Of these, wall layers are situated below the epidermis and mass of sporogenous cells near

the centre of the lobe.

• The epidermis is followed by alayer or two of parenchymatous wall layers. The innermost

wall layer is called tapetum. It is nutritive in function.

• The sporogenous cells lie inside the wall. These act as pollen or microspore mother cells

and divide meoitically.

• In the middle of the anther lobe,procambial strand is present.

Structure of mature anther

• An organized anther is four chambered in

atransection.

• The wall consists of an outer epidermis,

an endothecium, one to three middle

layers and an innermost tapetum.

• The tapetum at maturity is multinucleate

and contains dense cytoplasm which is

finally used up by the developing

microspores.

• Prior to dehiscence, the tapetum and also

the middle layers degenerate. The cells of

the endothecium are radially elongated

and exhibit, characteristic fibrous

thickenings.

• The microspores or pollen grains are at

first arranged in tetrads, (as a result of

reduction division of the microspore

mother cells). Later, these separate and

occur as individual pollen grains,

dispersed throughout the chamber. Each

shows characteristic shape, size and

structure.


189

Study of development of male gametophyte from the permanent slides under the

microscope.

The pollen grains/microspores germinate on the stigma of the same or different flower, as a

result of which there is development/formation of a structure called male gametophyte.

Development:

1. Each stamen consists of a lobed anther,

containing the microsporangia and

supported by a thin filament.

2. Meiosis of the diploid microspore

mother cells in the anther produces four

haploid microspores.

3. Each of these develops into a pollen

grain consisting of a larger vegetative

cell (also called the tube cell) inside of

which is a smaller germ cell (also

called the generative cell).

4. At some point, depending on the

species, the germ cell divides by mitosis

to produce 2 sperm cells.

5. At the time of pollen dispersal it may

be at 2 cell stage or 3 cell stages

depending upon the species.

6. When generative cell divides after

reaching the stigmatic surface it gives

rise to two male gametes.

7. The pollen tube comes out of the germ

pores present in the pollen grain. The

tube elongates and enters through the

style into the ovule.

8. This structure, a germinated pollen

grain carrying a long pollen tube and

two male gametes inside it, is termed as

a mature male gametophyte.


190

To study the structure of pollen grains using whole mounts

The pollen grain is the male gametophyte in gymnosperms and angiosperms, i.e. the structure that

produces the male gametes and transfers them to the female part. The grains derive from the meiotic

process of the pollen mother cells and at maturity usually consist of a bi or trinucleate cell surrounded by a

wall that has the important function of protecting the microgamethophyte in its journey between male and

female flowers. The pollen grain wall is very resistant to water loss and environmental injuries, primarily

to avoid damage and desiccation during the aerial journey.

Each species elaborates a distinctive sculpture on the surface of the pollen grains, and there are also many

other morphological characteristics that are useful for the pollen analyst in the classification of the pollen.

TYPES OF APERTURES IN MICROSPORES

The first characteristic to be considered when identifying pollen grains are the apertures. An

aperture is a thin or missing part of the exine, which is independent of the patterning of the exine.

Two different types of apertures can be distinguished: pores and fissures (colpi). The latter are

more primitive, they are elongated with pointed ends. Pores are usually isodiametric. They can

also be slightly elongated but, in contrast to colpi, they have rounded ends. In some pollen

grains, the exine around the apertures is either thicker or thinner. In pores this border is termed

annulus (typical in grass pollen) and in colpi margo (e.g. in Hedera helix). Pollen grains with

pores are porate and those with colpi are colpate. If both pore and colpus are combined in the

same aperture, the pollen grain is colporate.

Microspores can be divided into groups according to the number, position and type of apertures.

This classification is simple and consistent. The number of apertures is indicated by the prefixes

mono-, di-, tri- tetra-, penta-, hexa- and poly- with the above terms porate, colpate oder

colporate. Usually three pores and/or colpi are present that are regularly spaced around either the

edge or the equator of the pollen grain, depending on whether the pollen grain is seen from the

polar or equatorial view. If more than three apertures are present, they can either be regularly


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spaced around the edge, or equator respectively, (zonoporate/zonocolpate), or over the entire

surface (pantoporate/ pantocolpate).

The so-called syncolpate pollen grains have two or more colpi that are fused at the ends. These

colpi can sometimes form a spiral. Fenestrate pollen grains form a further group. They have large

window-like spaces, where the tectum is missing. (See chapter 2.3), the Asteraceae

(Cichorioideae), among others, belong to this group. Inaperturate pollen is rare microspores

without apertures (Juniperus). The Cyperaceae, for example, have more or less round apertures

in the ectexine, but, unlike pores, these do not have a clear margin and are termed lacunae (sing.

lacuna). In some pollen grains, e.g. birch and alder, the two layers of the exine are separated

around the pores and form a chamber between the inner and outer exine (vestibulum). Finally

there are the so-called bisaccate (pollen grains with "air-bags", e.g. the conifers spruce, pine,

Pinus cembra and fir.

The cell-wall structure of fern- and moss-spores differs from that of pollen grains and the spores

do not have pores or colpi. They merely have a fissure in the sexine. Manolete spores only have a

single fissure; trilete spores have three fissures that form a 'Y' ("Mercedes star").


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193

Procedure- selects young floral buds, take out the anthers with the help of fine forceps and open it with

needle. Spray the pollen on a mixture of 2% acetocarmine+50%glycerine (one drop each).cover with

cover slip and observe under the microscope.

Morphological aspects of some pollen grains-

1. Rosa indica (family- Rosaceae)

Minute,four lobed,exine-smooth,four furrows

and orange coloured.

2. Hibiscus rosa-sinensis (family-Malvaceae)

Grains pantoporate, spheroidal, pore-size, 10

um, surface spiniferous, interspinal areas

reticulate.

3. Datura stramonium( family-Solanaceae)

Grains 3-zonocolporate, spheroidal, size 46x47

u (43-49x 43-52 u), tips acute, exine thicker

than intine, tegillate. Exine surface striated, in

some reticulate.

4. Chenopodium sp (family-Chenopodiaceae)

Pollen grains are small as well as large sized.

Exine smooth with slightly corrogated

ornamentation.

5. Helianthus annuus (Family-Asteraceae)

Grains 3-zonocolporate, spherical, surface

spiniferous and sticky.


15 Pollen viability using in vitro

Requirements- fresh flowers (any easily available flower), cavity slides, cover slip, microscope,

sugar, and boric acid.

Theory- pollen grains primary cells involved in the development of male gametophyte. These

germinate under specific chemical environment under favorable condition. If a pollen grain

germinates, it is considered as viable.

Procedure-

• Prepare a nutrient solution

• Add a pinch of boric acid to this solution .shake well till it is dissolved properly.

• Clean the cavity slide and put a drop of the solution in the cavity.

• Remove mature anthers from the fresh flower. Burst them o

the pollen grains with the help of a brush and transfer them into the cavity containing

culture solution.

• Cover it with a coverslip and place the slide undisturbed for few hours.

• Remove the coverslip carefully and mount it on

• Observe it under the microscope. Record your observations by counting the number of

total and germinated pollen grains with pollen tubes in a microscopic field.

Observation-


in vitro pollen germination.

fresh flowers (any easily available flower), cavity slides, cover slip, microscope,

pollen grains primary cells involved in the development of male gametophyte. These


germinates, it is considered as viable.

Prepare a nutrient solution by dissolving 1.5g sugar in 100ml of water.

Add a pinch of boric acid to this solution .shake well till it is dissolved properly.

Clean the cavity slide and put a drop of the solution in the cavity.

Remove mature anthers from the fresh flower. Burst them on a clean glass slide. Collect


Cover it with a coverslip and place the slide undisturbed for few hours.

Remove the coverslip carefully and mount it on a slide containing a drop of safranin.

Observe it under the microscope. Record your observations by counting the number of


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fresh flowers (any easily available flower), cavity slides, cover slip, microscope,

pollen grains primary cells involved in the development of male gametophyte. These


Add a pinch of boric acid to this solution .shake well till it is dissolved properly.

n a clean glass slide. Collect


a slide containing a drop of safranin.

Observe it under the microscope. Record your observations by counting the number of



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Calculation: ��

��

Precautions –

1. Flowers should be freshly pluckedand should have mature anthers.

2. Allow pollen grains to germinate for sufficient time.

3. Allow pollen germination under closed environment i.e. by using cavity slide.

4. Use clean slide to observe the pollen germination.


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16 Structure of ovule and embryo sac development from permanent slides.

Ovule is defined as integumented megasporangium. It encloses embryo sac which is the

female gametophyte of angiosperms. Following are the types of ovules.

Structure of Female Gametophyte of angiosperms

Orthotropous ovule: the micropylar end, chalazal end

and funicle all lie in single vertical line, also called as a

straight ovule. Eg. Polygonum, piper.

Anatropous ovule: The body of ovule gets inverted at

180 degrees so that micropyle of th embryo sac comes to

lie towards the hilum and funicle. Chalazal end occupies

the upper end. It is also called as the inverted ovule. E.g.

Solanaceae, compositae.

Hemitropous ovule: The body of ovule gets curved at

90 degrees with respect to funicle, therefore funicle and

micropyle are at 90 degree angle to each other. The

embryo sac is placed transeversely inside the ovule. Eg.

Ranunculaceae,crucifers.

Campylotropous ovule: Here the body of the ovule gets

curved at an angle, but the embryo sac remains straight

inside it. The micropylar end and funicle come closer to

each other. Eg. Capsella, mustard

Amphitropous ovule: Here the body of the ovule as well

as the embryo sac gets curved so that embryo sac attains

a horse-shoe shape. The funicle and micropylar ends are

closer to each other. Eg. Crucifers, papaveraceae.

Circinotropous ovule: Here the funicle of the ovule

takes a 360 degree curve so that micropyle again comes

to lie at the upper end. The funicle completely encircles

the ovule on all sides so that it seems like a third

integument for the ovule. Eg. Opuntia (cactaceae)


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Structure of embryo sac/female gametophyte:

1. Embryo sac/female gametophye is an oval

structure within an ovule of an angiosperm

that contains the egg. Together with the

fertilized egg, it develops into a seed. The

upper end where egg apparatus lies is called as

the micropylar end from where the pollen tube

enters the ovule.

2. The embryo sac is the female gametophyte of

angiosperms, consisting of eight nuclei: the

egg and two adjacent and short-lived

synergids that are near the micropyle .the

synergids are also called potential cells.

3. Two polar nuclie in the central cell. These

fuse with one of the male nucleus to form

primary endosperm nucleus in future, to give

rise to endosperm tissue after the syngamy has

taken place.

4. Three antipodal nuclei at the chalazal end of

the embryo sac opposite the micropyle. Like

the synergids, these nuclei degenerate at or

shortly after fertilization. They pass on all the

nourishment they get from nucellus to the

potential egg cell.


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Development of Female gametophyte in Angiosperms

Development:

During megasporogenesis, the diploid megaspore mother cell undergoes meiosis and gives rise to four

haploid nuclei. Angiosperms exhibit three main patterns of megasporogenesis, referred to as

monosporic, bisporic, and tetrasporicIn the monosporic pattern, both meiotic divisions are

accompanied by cell plate formation, resulting in four one-nucleate megaspores. Subsequently, three

megaspores, generally the micropylar-most megaspores, undergo cell death. In the bisporic pattern,

cell plates form after meiosis I but not meiosis II. The result is two two-nucleate megaspores, one of

which degenerates. In the tetrasporic pattern, cell plates fail to form after both meiotic divisions,

resulting in one four-nucleate megaspore. Thus, these three patterns give rise to a single functional

megaspore that contains one (monosporic), two (bisporic), or four (tetrasporic) meiotic nuclei. The

monosporic pattern is the most common form and is represented within the Polygonum pattern. During

megagametogenesis, the functional megaspore gives rise to the mature female gametophyte. Initially,

the megaspore undergoes mitosis without cytokinesis, resulting in a multinucleate coenocyte.

Subsequently, cell walls form around these nuclei, resulting in a cellularized female gametophyte. For

example, in the Polygonum-type pattern, a single nucleus undergoes two rounds of mitosis, producing

a four-nucleate cell with two nuclei at each pole. During a third mitosis, phragmoplasts and cell plates

form between sister and nonsister nuclei, and soon thereafter, the female gametophyte cells become

completely surrounded by cell walls. During cellularization, two nuclei, one from each pole (the polar

nuclei), migrate toward the center of the developing female gametophyte and fuse together either

before or upon fertilization of the central cell. These events result in a seven-celled structure consisting

of three antipodal cells, one central cell, two synergid cells, and one egg cell. The monosporic,

Polygonum type of female gametophyte is typically a seven-celled structure at maturity.


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17 Nuclear and cellular endosperm. Embryo development in monocots and dicots

(using permanent slides/dissection).

Endosperm and Endosperm Formation:

Endosperm is the name of food laden tissue which is meant for nourishing the embryo in seed

plants. In gymnosperms; it represents the female gametophyte. In angiosperms, the endosperm is a

special tissue which is formed as a result of vegetative fertilization or fusion of a male gamete with

diploid secondary nucleus of the central cell.

The endosperm of angiosperms establishes a physiological compatibility with the developing hybrid

embryo, since it has the genome of the male gamete also within it. Vegetative fertilization gives rise

to a primary endosperm cell having a triploid endosperm nucleus.

Depending upon the mode of its formation, angiospermic endosperm is of the following types:

1. Nuclear Endosperm:

In this type, the first division of the primary endosperm cell and several of the following ones are

unaccompanied by cell wall formation. The nuclei may either remain free or in later stages they

become separated by walls, e.g., many Archichlamydeae and Monocots.

2. Cellular Endosperm:

In the cellular type, the first, and most of the subsequent division are accompanied by wall

formation so that the embryo sac becomes divided into several chambers, e.g., most gamopetalae.

3. Helobial Endosperm:

In the helobial type (so called because of its frequent occurrence in the order Helobiales) the first

division of primary endosperm nucleus is followed by cytokinesis to form two cells, micropylar and

chalazal. Further development in both the cells occur like that of nuclear endosperm i.e.,

multinucleate stage followed by wall formation, e.g. Helobiales.

During its growth the endosperm crushes the nucellus. It is in turn eaten by growing embryo. The

endosperm may persist in the seed when the latter is called endospermic or albuminous (e.g.,

Castor). In others, the endosperm is completely absorbed by the growing embryo and the food

reserve gets stored in the cotyledons. Such seeds are called non-endospermic or exalbuminous, e.g.,

Cucurbita.


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Embryo development in dicots

Embryogeny (Embryo Formation):

Embryogeny is the sum total of changes that occur during the development of a mature embryo

from a zygote or oospore. In a typical dicot, the zygote elongates and then divides by a

transverse wall into two unequal cells.

The larger basal cell is called suspensor cell. The other towards the antipodal end is termed as

terminal cell or embryo cell. The suspensor cell divides transversely a few times to produce a

filamentous suspensor of 6—10 cells.

The suspensor helps in pushing the embryo in the endosperm. The first cell of the suspensor

towards the micropylar end becomes swollen and functions as a haustorium. The haustorium has

wall ingrowths similar to transfer cells. The last cell of the suspensor at the end adjacent to the

embryo is known as hypophysis. Hypophysis later gives rise to the radicle.

The embyro cell undergoes two vertical divisions and one transverse division to form eight cells

arranged in two tiers—epibasal (terminal) and hypobasal (near the suspensor). The epibasal

cells eventually form the two cotyledons and the plumule. Only one cotyledon is produced in

monocots (e.g. Wheat, Maize, Onion, and Palm). The hypobasal cells produce the hypocotyl

except its tip.

The eight embryonic cells or octants divide periclinally to produce an outer layer of protoderm

or dermatogen. The inner cells differentiate further into procambium and ground meristem.

Protoderm forms epidermis, procambium gives rise to steal or vascular strand and ground

meristem produces cortex and pith.

Initially the embryo is globular and undifferentiated. Early embryo with radial symmetry is

called proembryo. It is transformed into embryo with the development of radicle, plumule and

cotyledon. Two cotyledons differentiate from the sides with a faint plumule in the centre.

At this time the embryo becomes heart-shaped. The rate of growth of the cotyledons is very high

so that they elongate tremendously while the plumule remains as a small mound of

undifferentiated tissue. Subsequently, the embryo undergoes rest as the ovule gets transformed

into seed. In some plants the embryo remains in the globular or spherical form even at the time

of seed shedding without showing any distinction of plumule, radicle and cotyledons, e.g.,

Orobanche, Orchids, Utricularia.


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Embryo development in monocots

Embryogeny in Monocots:

The zygote or oospore elongates and then divides transversely to form basal and terminal

cells. The basal cell (towards micropylar end) produces a large swollen, vesicular

suspensor cell. It may function as haustorium. The terminal cell divides by another

transverse wall to form two cells.

The top cell after a series of divisions forms plumule and a single cotyledon. Cotyledon

called scutellum, grows rapidly and pushes the terminal plumule to one side. The plumule

comes to lie in a depression.

The middle cell, after many divisions forms hypocotyl and radicle. It also adds a few cells

to the suspensor. In some cereals both plumule and radicle get covered by sheaths

developed from scutellum called coleoptile and coleorhiza respectively.

Structure of Monocot Embryo:

The embryos of monocotyledons have only one cotyledon. In grass family (Gramineae),

this cotyledon is called scutellum. It is situated towards lateral side of embryonal axis.

This axis at its lower end has radicle and root cap enclosed in a sheath called coleorhiza.

The part of axis above the level of attachment of scutellum is called epicotyl. It has as

shoot apex and few leaf primordia enclosed in a hollow foliar structure called coleoptile.

Epiblast represents rudiments of second cotyledon.


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18 Simple experiments to show vegetative propagation (leaf cuttings in bryophyllum,

begonia; stem cuttings in rose, money plant, sugarcane and bougainvillea).

Introduction-

Vegetative propagation produces the next generation that is genetically identical to the parent.

Such an organism that is genetically identical to the parent is called a clone. In case of plants

with advantageous characteristics, the characteristics can be preserved by producing clones. This

is particularly useful to agriculturists and horticulturists in order to get the best crop and uniform

yield every time.

There are various ways of carrying out artificial propagation of plants. Cutting, layering, grafting

and budding are some of the traditional methods whereas tissue culture is a recent technology.

Cutting

Cutting involves removing a piece of the parent plant - stem, root or leaf, and planting it in a

suitable medium. At first roots are produced and then the shoot with the leaves. If a stem is

taken, it must contain the nodal region. In some cases, rooting hormone may be required to

initiate root formation.

For example:

• Stem cutting is commonly done for rose, sugarcane, banana, geranium, etc.,

• Root cutting is done for dahlia

• Leaf cuttings are used for African violets.

Layering

Layering is the method of inducing certain branches of the parent plant to produce roots by

bending and pegging them to the ground around the parent plant leaving the tips exposed. Once

the roots develop the branch is then cut off from the parent body.

The branch that produces the roots is called the layer. It is a natural method in plants such as

black raspberries. However, it is induced in plants like Jasminum, Rhododendron, strawberries,

Magnolia, etc.

Grafting

It is the transfer of a part of one plant to the stump of another plant. The part taken from a plant

is a portion of the stem with many buds. This portion is called scion and is selected for the


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quality of its fruit. The stump to which the scion is attached is called the stock. Stock is selected

for qualities such as disease resistance and hardiness.

Grafting by Stem Cutting

The cut ends of both the scion and stock are shaped such that they complement each other and

their cambial tissues are close to each other. The two cut ends are brought together and covered

with grafting wax. After some time, the tissues of the scion and the stock become continuous.

The plant bears flowers and fruits characteristic of the scion.It is commonly practised on apple

trees and on such plants which either do not produce viable seeds or the seeds which have a lot

of variation.

Budding or Bud Grafting

It is a variation of the grafting method explained above. In this method, the scion is a bud along

with some bark. A 'T'-shaped cut is made on the stock into which the scion is inserted and bound

with a tape.


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Three Stages of Bud Grafting - Method of Cleft Grafting-The bud, once fixed, gives rise to new

branches. For example, bud grafting is done on roses, plums, peaches, pears, citrus, etc.

Stem cuttings-

Stem cuttings are the most important and greatest used type of cutting. In general, they can be

divided into 4 groups, the hardwood, semi hardwood, softwood or herbaceous and the cane

cutting. When preparing a stem cutting a section of stem tissue with lateral or terminal buds is

obtained, typically, stem cuttings are made from the terminal ends of shoots, generally 8-13cm

long and are removed from the parent plant at a ppoint just below a healthy lea. As a general

rule,the stem cuttings( except hardwood and cane types) should have 3 to 4 leaves for quickest

rooting. The leaves from the basal 1/3 the stem cutting should be removed.

Hardwood cuttings-

These cuttings are prepared during the dormant season using wood from the previous season’s

growth, although in a few cases, older wood can be used. The length of hard wood cutting vary


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from 10-30 cm. older wood can be as long as 0.6-0.9 m. in most cases, cuttings of pencil

thickness, i.e. 0.6-1.2 cm in diameter with atleast 2 nodes are selected depending upon the

species.

Three types of hardwood cuttings can be prepared, the straight, the heel and the mallet cutting.

The heel hardwood cutting has attached at its base a small portion of older wood, while the

mallet type hardwood cutting includes short sections of older stem wood. The straight hardwood

cutting is entirely composed of 1 year wood.


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Vegetative propagation in Saccharum officinarum by stem cutting

• Select healthy seed material. It should be free from pests and diseases.

• High viability is essential for establishment of the crop. The top one third to half portion

of a cane being and is best to be used as seeds.

• Collect sets from well-matured erect and healthy cones.

• Before planting the sets leaves of the canes talk are removed without damaging the buds.

• Cut these stalks into 3 buds sets each, usually 30-50 cm long.

• Soak the sets in water for four to six hours before sowing.

• To prevent the sets from rot and pineapple disease, dip the sets in suitable fungicide such

as 0.25% mercuric acid or 0.25% aretan or agallol solution. Agallol along with gamma

BHC has been recommended for northern India.

• Plant the sets in farm using appropriate planting irrigation and manuring practices.


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Softwood cutting

Vegetative propagation in bougainvillea by stem cuttings

• Cut 7.5-10 cm long pieces of shoot with about 4-6 nodes and several leaves on

the terminal end.

• Remove the leaves from basal portion of stem cuttings.

• Give a cut at the base just below the node.

• Collect cuttings during cooler part of the day i.e. early in the morning.

• Treat the stem cuttings with optimum strength of 0.4% IBA depending on the

cultivar and time of the year. The basal cut and exposed part of stem is dipped

in the solution of IBA.

• Place the treated stem cutting with optimum temperature in the pot.

• Also provide intermittent mist. Bougainvillea do not tolerate wet environment.

Vegetative propagation in Rosa indica by stem cutting

When cuttings are prepared from the soft, succulent, herbaceous growth they are

termed softwood, herbaceous or green wood cuttings.an extremely wide range of

horticultural plants are propagated in this manner including chrysanthemums, fuschia

and geraniums among the greenhouse crops and roses, salix, moneyplant and

bougainvillea among the landscape plants.

The stem cuttings are generally 8-13 cm in length with leaves retained on the upper 2/3

to 1/2 of the cuttings. the herbaceous or softwood cutting should have 2or more nodes

and if the leaves are large, they may be cut in order to reduce water loss through

transpiration and save space.


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Leaf cuttings- whole leaf cuttings are prepared from leaves with or without petioles. When

petioles are not present the leaf is broken or cut off the plant and the basal or proximal edge of

the leaf is inserted into the rooting medium. Plants without petioles include sedum, jade and

cactus. Roots and leaves will eventually forn at base of the leaf. The petiole should not be more

than 4 cm long and should be set deep enough into the medium to keep the cuttings erect.

In addition, leaf cuttings can be prepared by taking leaf sections when propagating plants are like

Rex Begonia and snake plant (sanseveria sp.).

Vegetative propagation in begonia-

• Cut well matured leaves into triangular

sections in such a way that the two sides of

two triangular wedges are bordered by leaf

vein.

• Discard the outer thin section of leaf.

• Insert the medium leaf section upright in

sand.

• Place the pot in warm and humid conditions.

• Allow 5-6 weeks for plants to appear.

• The plantlets appear on the cut surface of the

large leaf veins near the leaf base.


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Vegetative propagation in Bryophyllum-

• The foliar embryos from leaf margins are

carefully removed.

• These are placed in rooting medium.

• Plantlets grow from foliar embryos or leaf

sections placed in rooting medium.


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19 Germination of dormant and non dormant seeds.

Theory- dormancy is defined as phenomenon of non-germination of seeds due to internal factors

under favourable condition.

Material required- xanthium seeds, petridish, beaker, conc. Sulphuric acid, cotton, blade,

distilled water etc.

Procedure-

• Take three sets of xanthium seeds each.

• Make splits in hard coat of Xanthium seeds of first set (5 seeds) and put these

seeds in a petridish containing well wet pad of cotton.

• Put seeds of second batch in a beaker containing conc. Sulphuric acid for few

hours. After some time, take out the seeds and wash well in running water to clear

out the sulphuric acid. Place these seeds for germination in a petridish with a wet

cotton seed.

• Place third set of seeds as such in a petridish for germination.

• Put the above three petridishes under same conditions of temperature, air and

light.

• Take care that cotton may not get dry.

• Note the time taken for germination by the seeds in the above three petridishes.


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Observations- the seeds of 3rd set did not germinate at all, while the seeds in 1

st and 2

nd set

germinate well.

Result- seeds didn’t germinate due to seed dormancy because of seed coat but acid and

mechanical treatment helps in breaking the dormancy.

Precautions-

1. Cotton pads should not get dry during germination study.

2. Acid should be washed completely for germination study.

3. Time taken for germination should be noted down carefully.

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