Exercise 11

Aim: Study and describe flowering plants of families Solanaceae, Fabaceae

and Liliaceae.

Principle: Taxonomy deals with identification, nomenclature and classification of

organisms. Bentham and Hooker's system of classification is universally used for
classification of plants. Field identification of plants is based primarily on
morphological features particularly the floral characters.

Requirement: Locally available plant specimens of Solanaceae, Fabaceae and

Liliaceae. (minimum 3 species for each family other than the ones described for
reference in the manual); each specimen should have at least a small branch with a
few inter nodes, leaves, flowers and fruits; glass slides, cover glass, water, 100 ml
beakers, petridish, razor, blade, needles, brush, hand lens, dissecting microscope and
compound microscope.

Procedure
Keep the twigs in beakers containing water. Make yourself familiar with the
terms given to describe the habit of plant, its root system, stem and leaf,
inflorescence and flowers. Describe the vegetative and floral features of the
plant in the same sequence using terms described therein. Observe the flower
bud under dissection microscope or a hand lens and note the aestivation
patterns of calyx and corolla, number of sepals and petals (tri, tetra, penta-
merous), number of stamens. Cut LS of the flower, place it on a slide and
observe under the dissecting microscope to study:
• Position (attachment) of stamens – opposite/alternate to petals; free or
epipetalous; extrorse/ introrse anthers (anther lobes in the bud face
away from axis – extrorse; anther lobes in the bud face towards the
main axis – introrse).
• Number of carpels (mono, bi, tri- carpellary); Position of the ovary
(epigynous, perigynous, hypogynous).
Mount a stamen on a slide and study the attachment of filament to anther
(basifixed, dorsifixed, versatile, adnate), dehiscence pattern of anther (porous,
longitudinal), number of anther lobes (monothecous, dithecous). Mount the
pistil and study the ovary, style and stigma. Also cut a TS of the ovary to
study the number of locules and placentation. Write the floral formula and

52
Exercise 11

draw the floral diagram of each specimen based on the description. Identify
features of the different parts of flower on the basis of descriptions given in
Table 11.1.

Observations
Compare the characters with those given in the table and identify the family
to which the plant belongs to.

Note: For ready reference some plants are described for each family. The students are required to
study the plants other than one described here-under.

Questions
1. Draw the floral diagram and write the floral formula from the below given description
of a flower-
Bisexual, actinomorphic, hypogynous, sepals 5, gamosepalous, petals 5, free,
imbricate aestivation, stamens 6, arranged in 2 whorls, ovary superior, trilocular,
axile placentation.
2. In which type of placentation would the ovary be always unilocular?
3. If a flower is epigynous what is the position of floral parts?
4. What in the fruit is equivalent to the ovule of the ovary?

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 Laboratory Manual: Biology

Table 11.1 Description of parts of flowers:

Calyx/Corolla

Aestivation Arrangement of sepals and petals with respect to one another

Aestivation (i) Valvate: The sepa ls/peta ls close to each other without
(Fig 11.1 a–e) overlapping or may be in contact with each other.
(ii) Twisted: Overlapping is regular, i.e., one margin of the sepal/
petal overlap the next member and the other margin is overlapped
by the previous.
(iii) Imbricate: Out of five sepals/petals one is completely
internal being overlapped on both margins and one is completely
external with the rest of the members arranged as in twisted
aestivation.
(iv) Quincuncial: Out of five sepals/petals two are completely
internal, two external and one has one margin external and the
other margin internal.
(v) Vexillary: Out of five sepals/petals the posterior one is
the largest and external almost completely covering two
lateral members which in turn overlap the two small anterior
sepals/petals
Number of stamens The number of stamens may vary from a few to many in dif-
ferent flowers
Cohesion Stamens may be free or united. If united they can be of the
(Fig. 11.2 a-e) following type:
(i) Syngenesious: Filaments free and anthers united, e.g.,
Sunflower.
(ii) Synandrous: Stamens fused all through their length. e.g.,
Cucurbita.
(iii) Adelphous: Anthers remain free and filaments are united.
Adelphous condition can be:-
(a) Monoadelphous - United to form 1 bundle. e.g.,
China rose.
(b) Diadelphous - United to form 2 bundles. e.g., Pea.
(c) Polyadelphous- United into more than two bundles.
e.g., Lemon.

Adhesion Fusion of stamens with other parts of the flower.

(Fig. 11.3) (i) Epipetalous: Stamens fused with petals
e.g., Sunflower, Datura.
(ii) Epiphyllous: Stamens fused with perianth
e.g., Lily.

(i) Basifixed: Filament attached to the base of anther.

Attachment of filament to e.g., Mustard.
anther
(ii) Adnate: Filament attached along the whole length of
(Fig. 11.4 a-d)
anther.
e.g., Michelia, Magnolia.

54
Exercise 11

(iii) Dorsifixed: Filament attached to the back of anther, e.g.,

Passion flower.
(iv) Versatile: Anther lobes attached with filament in the
middle portion with both ends free.
e.g., Gramineae family.

Lobes of anther (i) Monothecous: Anther single lobed.

(Fig. 11.5 a,b) (ii) Dithecous: Anther bi-lobed.

Dehiscence pattern (i) Porous: Pollens released through pores, e.g., brinjal,
(Fig. 11.6 a,b) potato.
(ii) Longitudinal: Pollens released through the longitudinal
slit of anther lobes, e.g., China rose, cotton.

Gynoecium

Position of ovary (i) Epigynous: Position of ovary inferior to other floral parts.
(Fig. 11.7 a-d) e.g., mustard, China rose.
(ii) Perigynous: Other floral parts (organs) are attached around
the ovary. e.g., apple, guava.
(iii) Hypogynous: Position of ovary superior to other floral parts
e.g., sunflower.

Cohesion If number of carpels is more than one, they may be

(Fig. 11.8 a-c) (i) Apocarpous: Carpels are free. Each carpel has its own style
and stigma. e.g., rose.
(ii) Syncarpous: Carpels are united, e.g., lady finger, tomato.

Number of locules in ovary Vary from one to many

(i) Unilocular: One locule, e.g., rose, pea.
(ii) Bilocular: Two locules. e.g., datura.
(iii) Multilocular: Many locules, e.g., lady’s finger, China rose.

Placentation (i) Marginal: The placenta forms a ridge along the ventral
(Fig. 11.9 a-e) suture of the ovary and the ovules are borne on this ridge
e.g., pea.
(ii) Axile: The ovary is partitioned into several chambers or
locules and the placentae are borne along the septa of the
ovary. e.g., tomato, China rose.
(iii) Parietal: The ovules develop on the inner wall of the ovary
or on peripheral part. Ovary unilocular but in some cases
becomes two chambered due to formation of a false septum.
e.g., mustard.
(iv) Free central: Ovules are borne on the central axis and
septa are absent. e.g., carnation, chilly.
(v) Basal: Placenta develops at the base of the ovary. e.g.,
sunflower.

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 Laboratory Manual: Biology

(b) (c)
(a)

(d) (e)

Fig. 11.1 Aestivation (a) Valvate (b) Twisted (c) Imbricate (d) Quincuncial
(e) Vexillary

(b) (c)
(a)

(d)
(e)

Fig. 11.2 C o h e s i o n o f s t a m e n s ( a ) S y n g e n e s i o u s ( b ) S y n a n d r o u s
(c) Monoadelphous (d) diadelphous (e) Polyadelphous

Fig. 11.3 Adhesion of Stamens-Epipetalous/Epiphyllous

56
Exercise 11

(a) (b) (c) (d)

Fig. 11.4 Attachment of filament to anther (a) Basifixed (b) Adnate

(c) Dorsifixed (d) Versatile

(a) (b)
Fig. 11.5 Anther lobes (a) Dithecous (b) Monothecous

(a)
(b)
Fig. 11.6 Dehiscence pattern of anther (a) Porous (b) Longitudinal

57
 Laboratory Manual: Biology

(c) (d)
(a) (b)

Fig. 11.7 Position of ovary (a) Epigynous (b-c) Perigynous (d) Hypogynous

(a) (b) (c)

Fig. 11.8 Cohesion of carpels (a) Apocarpous (b-c) Syncarpous

58
Exercise 11

(a) (b) (c)

(d)
(e)

Fig. 11.9 Placentation (a) Marginal (b) Axile (c) Parietal (d) Free central (e) Basal

59
 Annexure 1
60

Solanum Petunia alba Lathyrus sp. Pisum sativum Asphodelus

Characteristics
nigrum(Makoi, tenuifolius
Black night
shade)

Habit Herbaceous Herbaceous Herbaceous annual, Herbaceous annual, Herbaceous annual

annual annual climber climber

Root Tap root Tap root Taproot, the lateral Taproot, the lateral Fibrous root
roots may have roots may have
nodules which nodules which
contain nitrogen contain nitrogen
fixing Rhizobium fixing Rhizobium
bacteria bacteria

Stem Erect, Erect, Weak, cylindrical, Weak, cylindrical, Very small but
herbaceous, herbaceous, branched, branched, scape formed in
branched, solid, branched, solid, herbaceous, aerial, herbaceous, aerial reproductive
cylindrical, cylindrical, green climbing with help of climbing with help of phase
green leaf tendrils, green leaf tendrils, green

Leaf Ex-stipulate, Ex-stipulate, Stipulate (stipules Stipulate (stipules Fistular, slender

petiolate or sessile, simple, foliaceous and in large, ovate,
sessile, simple, alternate in the pairs), modified into a foliaceous), petiolate,
alternate, basal parts and tendril, simple, imparipinnately
reticulate opposite decussate alternate, reticulate compound, (leaf lets 4

Laboratory Manual: Biology

venation in upper parts, venation or 6) the common
reticulate venation rachis ends in a
branched tendril,
terminal leaflet is
always a tendril;
•

alternate leaflets with

reticulate venation

Inflorescence Cymose Solitary Racemose Racemose Racemose

 Exercise 11
Characteristics Solanum Petunia alba Lathyrus sp. Pisum sativum Asphodelus
nigrum(Makoi, tenuifolius
Black night
shade)
Flower Ebracteate, Bracteate, Bracteate, bracteolate, Bracteate, bracteolate, Bracteate,
ebracteolate, ebracteolate, pedicellate, complete, pedicellate, complete, ebracteolate,
pedicellate, pedicellate, zygomorphic, bisexual zygomorphic, bisexual pedicellate,
complete, complete, pentamerous, hypo-or pentamerous, hypo-or actinomophic,
actinomorphic, actinomorphic, perigynous, perigynous, bisexual,
bisexual bisexual, papilionaceous papilionaceous trimerous,
pentamerous, pentamerous, hypogynous
hypogynous hypogynous

Calyx Sepals 5, Sepals 5, Sepals 5, Sepals 5,

persistant, persistant, gamosepalous, gamosepalous,
gamosepalous, gamosepalous, ascending imbricate ascending imbricate
green, valvate green, valvate aestivation, odd sepal aestivation, valvate
aestivation aestivation anterior, green aestivation, odd sepal
anterior, green

Corolla Petals 5, Petals 5, Petals 5, polypetatous Petals 5, polypetatous Perianth tepaloid,

gamopetalous, gamopetalous, papilionaceous (The 5 papilionaceous (The 5 tepals 6 in two
white, valvate white/purple, petals are unequal and pe tals are unequal and whorls of 3 each
aestivation valvate aestivation have a bilateral symmetry. have a bilateral symmetry. (3+3), free, valvate
The posterior or outer The posteri or or outer aestivation
most largest petal is called most largest petal is called
standard, the lateral pair standard, the lateral pair
of petals which are clawed of petals which are clawed
are called the wings and are called the wings and the
the two anterior petals are tw o anterior petals are
•

united to form the keel united to form the keel

i.e., 1+2+2 arrangement), which encloses the
which encloses the stamens and the carpel,
stamens and the carpel i.e., 1+2+2 arrangement),
descending imbricate descending imbricate
(vexillary) aestivation (vexillary) aestivation
61
62

Characteristics Solanum Petunia alba Lathyrus Sp. Pisum sativum Asphodelus

nigrum(Makoi, tenuifolius
Black night
shade)
Androecium Stamens 5, Stamens 5, Stamens 10 arranged Stamens 10 arranged Stamens 6 in 2
epipetalous, epipetalous, in a single whorl, in a single whorl, alternate whorls of
alternate with alternate with diadelphous, (9+1 diadelphous, (9+1 3 each, epiphyllous
corolla lobes, corolla lobes, arrangement, 9 unite arrangement, 9 unite opposite to tepals,
polyandrous, filaments at the base and form a at the base and form a basifixed,
anthers unequal, tube around the ovary tube around the ovary dithecous.
dithecous, polyandrous, and the 10th posterior and the 10th posterior introrse,
introrse, anthers basifixed, stamen is free) stamen is free) dehiscence by
dehiscence by dithecous, anthers basifixed, anthers basifixed, longitudinal slits
apical pores introrse, dithecous, introrse, dithecous, introrse,
dehiscence by longitudinal longitudinal
apical pore dehiscence dehiscence

Gynoecium Bicarpellary Bicarpellary Monocarpellary, ovary Monocarpellary, ovary Tricarpellary

syncarpous, ovary syncarpous, ovary superior, unilocular, superior, unilocular, syncarpous, ovary
superior, superior, ovules many, ovules many, superior trilocular,
bilocular, ovary bilocular, ovary placentation marginal, placentation marginal two ovules in each
obliquely placed obliquely placed locule, axile
in the flower, in the flower, placentation,
ovules many per ovules many per
locule, axile locule, obliquely
placentation, transverse

Laboratory Manual: Biology

placenta swollen, septum, axile
placentation,
placenta swollen,
•

Fruit Berry Capsule Legume Legume Berry

Floral Ebr, Ebrl, ,Å, Ebr, Ebrl, ,Å , Br, brl, , %, K5 C1+2+2 Br, brl, , %, K5 C1+2+2 Br, Ebrl, ,Å,
formula
K(5) C5 A5 G (2) . K(5) C5 A5 G (2) . A(9)+1 G 1 .
A(9)+1 G 1 . G (3) .
Exercise 11

(a)
(b)
(c)
Fig. 11.10 Petunia (a) A twig (b) LS of flower (c) Floral diagram

(a) (b) (c)

Fig. 11.11 Lathyrus (a) A twig (b) LS of flower (c) Floral diagram

(a) (b) (c)

Fig. 11.12 Asphodelus (a) A twig (b) LS of flower (c) Floral diagram

63
Annexure 2
Other Examples

Family : Solanaceae Family : Fabaceae Family : Liliaceae

Physalis Phaseolus moong (Urad) Allium cepa (onion)

Solanum xanthocarpum P. vulgaris (Kidney bean, French bean) Gloriosa superba
Solanum melongena P. aureus (Moong) Aloe barbendesis
Solanum tuberosum T rigonella (Fenugreek) Heterosmilax
Nicotiana tabacum Cajanus cajan (Arhar, pigeon pea) Asparagus officinale
Hyocyamus Dolichos lablab (Sem, Hyacinth bean) Yucca gloriosa
Atropa belladonna Cicer arietinum (chana, gram, chickpea Lilium candidum
Withania somnifera Indigofera (Indigo) Smilax spp
Cestrum nocturnum Abrus (Ratti)
Datura Arachis hypogea (groundnut)
Medicago sativa (Alfalfa)

IDENTIFICATION AND SYSTEMATIC POSITION- Family : Solanaceae

1. Leaves reticulate venation, flowers tetra or pentamerous, tap root Dicotyledons

system.
2. Petals fused, Gamopetalae
3. Ovary superior, carpels usually two, stamens alternate with the Bicarpellatae
corolla lobes, number of stamens equal or fewer to the number of
corolla lobes.
4. Herbs or twiners, leaves alternate, flowers actinomorphic, Polemoniales
stamens epipetalous, ovary superior two carpels, bilocular, axile
placentation, ovules few or many in each carpel.
5. Herbs and shrubs, leaves simple, alternate, gamosepalous, Solanaceae
stamens 5, epipetalous, ovary superior, bicarpellary syncarpous,
bilocular, sometimes four locules due to false septum, many
ovules in each locule, swollen placenta, ovary obliquely placed in
the flower, axile placentation, fruit a berry or a capsule.

IDENTIFICATION AND SYSTEMATIC POSITION - Family : Fabaceae

1. Leaves with reticulate venation, flowers tetra or pentamerous, tap Dicotyledons

root system.
2. Petals free or not united. Polypetalae
3. Flowers hypo or perigynous; regular or irregular (vexillary). Calyciflorae
4. Flowers zygomorphic and papilionaceous, descending imbricate Fabaceae
aestivation of corolla, 1 standard, 2 wings and 2 keels;
stamens10, mono or diadelphous (9+1) ovary superior, marginal
placentation, ovules many.

64
Exercise 11

IDENTIFICATION AND SYSTEMATIC POSITION - Family : Liliaceae

1. Leaves usually with parallel venation, flowers trimerous, fibrous Monocotyledonous

root system, embryo with one cotyledon
2. Ovary superior, trilocular, 6 tepals in 2 whorls of 3+3, petaloid Coronariae
3. Perianth petaloid, 6 tepals free or connate below. stamens 6 in Liliaceae
two whorls of 3+3, opposite to tepals, epiphyllous, ovary
tricarpellary, syncarpous, trilocular, 2 or more ovules per locule
fruit 3 celled berry or capsule.

65
Exercise 12
Aim: To study anatomy of stem and root of monocots and dicots.

Principle: The study of internal morphology, i.e., cells of various tissues in an organ of a
living body is called Anatomy. Tissue, which is a group of cells performing a common
function, may be simple (parenchyma, collenchyma and sclerenchyma) or complex
containing more than one type of cells (xylem and phloem). The tissues may be temporary
(meristematic) or permanent (sclerenchyma, parenchyma, collenchyma).
The internal organisation of these tissues differ in root, stem and leaves. These differences
are given in tabular form for easy identification. Various tissues which constitutes roots
and stems are described briefly.

Requirement: Samples of stem and root of sunflower, Cucurbita, maize, Canna, etc., or
any other locally available plant, safranin stain, dilute acid water, glycerine, watch glass,
slide, cover slip, brush, razor/scalpel blade, blotting paper, microscope.

Procedure
• Collect a few thin green branches of recent growth (i.e., non-woody/
herbaceous without any secondary growth) from the examples given
above, preferably of the thickness of a tooth-pick.
• Use pith of potato piece/Calotropis stem/raw papaya fruits for
embedding the material to be sectioned. It is advisable to first stain
roots before sectioning. If material is thick like that of maize, it can
be directly sectioned without embedding them in pith.
• Hold the material between the thumb and index finger in such a way
that the tips of the finger and smooth cut surface of the material are
in a line, while the tip of the thumb is just a few mm below the upper
surface of the material.
• Wet the surfaces of razor blade/scalpel blade.
• Carefully move the blade horizontally over the surface of material in
quick succession in a manner that a very thin and complete slice of
the material is cut and obtained over the surface of razor blade.
• After cutting several sections in this manner, transfer all these into a
watch glass containing water.

66
Exercise 12

• Make a visual observation of the sections cut and pick the thinnest
possible and complete sections from the lot and transfer it into a
watch glass containing safranin and allow these to remain there for
about 2 mins.

• With the help of a brush gently transfer the section into another
watch glass containing water to remove excess of safranin stain.
Keep the material for few minutes and transfer it into a watch glass
containing a few drops of dilute acid in water to remove excess of
safranin stain. Wash with water and transfer the section on to a
clean slide containing 1 drop of glycerine. Place a cover slip over it
avoiding air bubbles.

Observation
Note all tissues which are lignified (as in sclerenchyma, collenchyma) are
stained red with safranin. Observe the outline of the cut sections. Make a
note of the presence and composition of various tissues (epidermis, cortex,
endodermis, pericycle, vascular bundle) and characteristics of vascular
bundle. List the differences between root and stem of monocots and dicots.
Use the information given in Annexure 3 for identification.

Anatomically root differs from stem by the following points:

S.No. Root Stem

1. Cuticle absent Cuticle present

2. Epidermis does not have Epidermis contains stomata
stomata
3. Unicellular root hairs present Epidermal hairs are usually
multicellular
4. Collenchyma absent Collenchyma present
5. Green plastids absent Green plastids present
(achlorophyllous) (chloropyllous)
6. Vascular bundles are radial Vascular bundles are conjoint
in arrangement (xylem and and collateral in arrangement
phloem are on different radii) (xylem and phloem are on the
same radius)
7. Xylem development is Xylem development is centrifugal
centripetal and protoxylem is and protoxylem is endarch, i.e.,
exarch, i.e., lies towards the lies towards the center
periphery

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 Laboratory Manual: Biology

Annexure 3

Anatomy of the Root

The most distinguishing anatomical characters of the root are:
1. Epidermis: It is the outer most layer of thin walled parenchymatous cells
with many unicellular root hairs. It does not have stomata and cuticle.
2. Cortex: It is multilayered and well developed. The cells are thin walled,
parenchymatous and may contain leucoplasts. The intercellular spaces
are well developed. Collenchyma is absent. The inner most layer of the
cortex is called endodermis. The endodermis is a definite ring like layer
consisting of barrel shaped cells compactly arranged without any
intercellular spaces. Casparian thickenings in the form of strips are present
on the radial and inner walls of the endodermal cells. Also, passage cells
are present. The passage cells are thin walled and are usually located
opposite the protoxylem.
3. Pericycle: The outer most layer of the stele (vascular tissue) is called
pericycle. It is single layered and consists of compactly arranged thin walled
parenchymatous cells with no intercellular spaces. The pericycle cells
alternate with the endodermal cells suggesting that these two layers differ
in their origin. The endodermis is derived from periblem initials of the apical
meristem, whereas the pericycle is derived from the pleurome initials.
Pericycle encloses the vascular system.
4. Vascular system: Bounded by the endodermal and pericycle layers, vascular
system consists of xylem, phloem and the associated parenchyma tissue
called conjunctive tissue.
The vascular bundles are arranged in a ring. The bundles are radial
and there are equal number of separate bundles of xylem and phloem. The
number of xylem and phloem bundles varies from two to six (diarch, triarch,
tetrarch, pentarch, and hexarch) in dicots and more than six, i.e., polyarch
in monocots.
The xylem consists of protoxylem which lies towards periphery and
metaxylem which lies towards the centre or pith. This type of arrangement
of xylem is called exarch (protoxylem is exarch in root and endarch in
shoot). The protoxylem consists of annular and spiral vessels with narrow
lumen (in cross section) and the metaxylem consists of reticulate and pitted
vessels with broad lumen. (Recall the xylem maceration experiment)
The phloem consists of sieve tubes, companion cells and phloem
parenchyma.
The parenchyma present in between the xylem and phloem bundles is
known as conjunctive tissue.
5. Pith: It occupies the central area and may be large, small or even, absent.
Generally in dicot roots the pith is small or absent. Total obliteration of pith
occurs sometimes when metaxylem elements grow and meet in the centre.
In monocot roots pith is large in size. Pith consists of parenchymatous cells
with intercellular spaces.

68
Exercise 12

Anatomy of the Shoot

The central ascending portion of the plant axis is called the shoot. It develops
from the plumule of the embryo. The shoot bears lateral appendages called
leaves.
The anatomical feature of stem are:
1. Epidermis: It is the outermost layer of cells, generally parenchymatous
rectangular in shape. Multi-cellular trichomes or epidermal hairs,
(no epidermal hairs in monocots) are generally present. The epidermis has
an outer layer of cuticle made up of waxy material.
2. A multilayered hypodermis is present just below the epidermis. The
hypodermis is generally collenchymatous in dicots and sclerenchymatous
in monocots.
3. Cortex and pith are well defined in cases of dicots whereas in monocots
only ground tissue is present. In dicots well defined endodermis and pericycle
below the cortex are present. In monocots the endodermis is present around
each vascular bundle. Distinction into cortex, pericycle, and pith is not
seen. Vascular bundles are present in the ground tissue.
4. Each vascular bundle consists of xylem, phloem, cambium (absent in
case of monocots) and associated parenchyma tissue. The vascular
bundles are conjoint and collateral. They are open (i.e., cambium present
between xylem and phloem) in dicot stems and thus show the secondary
growth. Cambium is absent in monocot stems and therefore there is no
secondary growth with a few exception.
The vascular bundles are arranged in a ring in dicots whereas they are
scattered in ground tissue in monocots. Each vascular bundle is surrounded
by a sclerenchymatous bundle sheath.
The vascular bundles are usually of equal size in dicots whereas in
monocots they are of unequal size. In monocot stem the bundles near the
periphery or closer to epidermis are smaller in size and the bundles nearer
to the center are larger in size.
5. The protoxylem is endarch, i.e., towards the centre. The phloem consists of
sieve tubes, companion cells and phloem parenchyma.
In dicot stems, in between the xylem and phloem of the vascular bundle a
procambium strip of 2-3 cells thickness (fascicular cambium) is present.
The procambium between two adjacent vascular bundles is called
interfascicular cambium. In young stems the cambial strips are confined
only to the vascular bundles but as the stem becomes older, the
interfascicular cambium develops and a continuous ring of cambium is
formed. The secondary growth (formation of secondary phloem and
secondary xylem) is due to the activity of cambium.
6. In dicot stem the central region of the stem is called pith (medulla).
The pith consists of thin walled parenchymatous cell with intercellular
spaces. The pith is well developed in dicot stem whereas in monocots it
is absent.

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 Laboratory Manual: Biology

From the anatomical point of view the monocot and dicot roots differ from
each other in the following features (Fig. 12.1 and 12.2):

S. Monocot Root Dicot Root

No.
1. Polyarch condition Diarch to hexarch (2-6 vascular
bundles) condition
2. Pith well developed Pith is very small or absent

3. Secondary growth absent Secondary growth occurs due to

the activity of vascular cambium

Root hair
Root hair

Epidermis
Epidermis

Cortex
Cortex

Endodermis
Endodermis Pericycle
Pericycle
Phloem
Xylem Xylem
Phloem Pith

Pith

Fig. 12.1 TS of a monocot root Fig. 12.2 TS of a Dicot root

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Exercise 12

A few examples of dicotyledonous and monocotyledonous roots which can be

selected for anatomical study are given in the following table.

Dicotyledonous Roots Monocotyledonous Roots

Phaseolus radiatus Canna

Ranunculus Zea mays
Cicer Smilax
Ficus Allium cepa

Anatomically, the dicot and monocot stems differ in the following features
(Figs. 12.3 and 12.4):

Epidermis
Hypodermis

Cortex

Bundle sheath
Phloem

Xylem

Ground tissue
Epidermal
hair
Epidermis

Fig. 12.3 TS of a monocot stem Cortex Hypodermis

Endodermis
Pericyde
Phloem

Cambium
Xylem

Fig. 12.4 TS of a dicot stem

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 Laboratory Manual: Biology

S. Monocot Stem Dicot Stem

No.
1. Epidermis single layered and Epidermis single layered and
no epidermal hairs epidermal hairs are present
2. Hypodermis Hypodermis collenchymatous
sclerenchymatous
3. The vascular bundles are The vascular bundles are
scattered in arrangement arranged in a ring
4. The vascular bundles at the The vascular bundles are of the
periphery are smaller in size same size
than those at the center
5. The vascular bundles are The vascular bundles are
conjoint, collateral and conjoint, collateral and open; the
closed; the sclerenchymatous bundle sheath is absent; the
bundle sheath is present; the vessels are arranged in rows;
vessels are arranged in V- or water cavity is absent
Y-shape; water cavity is
present
6. Only ground tissue is present A well defined cortex,
endodermis, pericycle and pith
are present

A few typical dicotyledonous stems and monocotyledonous stems that can be

selected for study of anatomical are given in the following table.

Dicotyledonous Stems Monocotyledonous Stems

Helianthus (sunflower) Zea mays (maize/corn)

Tinospora Canna
Ricinus (castor) Asparagus
Xanthium Cynodon dactylon (Doob grass)

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Exercise 12

Questions
1. Arrange the following sequentially as you would see in a TS of a dicot stem-pericycle,
epidermis, pith, cortex, xylem, phloem.
2. Where do you find radial, conjoint, collateral and open vascular bundles?
3. What type of xylem arrangement would be seen in TS root of lily plant?
4. Which part of dicot stem is meristematic?

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