MORPHOLOGY OF FLOWERING PLANTS 67

5.1.1 Regions of the Root

The root is covered at the apex by a thimble-like
structure called the root cap (Figure 5.3). It
protects the tender apex of the root as it makes
its way through the soil. A few millimetres above
the root cap is the region of meristematic
activity. The cells of this region are very small,
thin-walled and with dense protoplasm. They
divide repeatedly. The cells proximal to this
region undergo rapid elongation and
enlargement and are responsible for the growth
of the root in length. This region is called the
region of elongation. The cells of the elongation
zone gradually differentiate and mature. Hence,
this zone, proximal to region of elongation, is
called the region of maturation. From this
region some of the epidermal cells form very fine Figure 5.3 The regions of the root-tip
and delicate, thread-like structures called root
hairs. These root hairs absorb water and
minerals from the soil.

5.1.2 Modifications of Root

Roots in some plants change their shape and
structure and become modified to perform
functions other than absorption and
conduction of water and minerals. They are
modified for support, storage of food and
respiration (Figure 5.4 and 5.5). Tap roots of
carrot, turnip and adventitious roots of sweet
potato, get swollen and store food. Can you give
some more such examples? Have you ever
wondered what those hanging structures that
support a banyan tree are? These are called
prop roots. Similarly, the stems of maize and
sugarcane have supporting roots coming out
of the lower nodes of the stem. These are called
stilt roots. In some plants such as Rhizophora
growing in swampy areas, many roots come out
of the ground and grow vertically upwards.
Such roots, called pneumatophores, help to Figure 5.4 Modification of root for support:
get oxygen for respiration (Figure 5.5b). Banyan tree

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Turnip Carrot Sweet

potato
Asparagus
(a) (b)
Figure 5.5 Modification of root for : (a) storage (b) respiration: pneumatophore in
Rhizophora

5.2 THE STEM

What are the features that distinguish a stem from a root? The stem is the
ascending part of the axis bearing branches, leaves, flowers and fruits. It
develops from the plumule of the embryo of a germinating seed. The stem
bears nodes and internodes. The region of the stem where leaves are
born are called nodes while internodes are the portions between two nodes.
The stem bears buds, which may be terminal or axillary. Stem is generally
green when young and later often become woody and dark brown.
The main function of the stem is spreading out branches bearing
leaves, flowers and fruits. It conducts water, minerals and photosynthates.
Some stems perform the function of storage of food, support, protection
and of vegetative propagation.

5.2.1 Modifications of Stem

The stem may not always be typically like what they are expected to be.
They are modified to perform different functions (Figure 5.6). Underground
stems of potato, ginger, turmeric, zaminkand, Colocasia are modified to
store food in them. They also act as organs of perennation to tide over
conditions unfavourable for growth. Stem tendrils which develop from
axillary buds, are slender and spirally coiled and help plants to climb
such as in gourds (cucumber, pumpkins, watermelon) and grapevines.
Axillary buds of stems may also get modified into woody, straight and
pointed thorns. Thorns are found in many plants such as Citrus,
Bougainvillea. They protect plants from browsing animals. Some plants
of arid regions modify their stems into flattened (Opuntia), or fleshy
cylindrical (Euphorbia) structures. They contain chlorophyll and carry

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Axillary bud
modified
Ginger into tendril

Potato
Zaminkand
(b)
(a)

Stem modified
into spine

Bougainvillea sp. Roots arising

Oxalis sp.
(c) from nodes
(d)

Figure 5.6 Modifications of stem for : (a) storage (b) support (c) protection
(d) spread and vegetative propagation

out photosynthesis. Underground stems of some plants such as grass

and strawberry, etc., spread to new niches and when older parts die new
plants are formed. In plants like mint and jasmine a slender lateral branch
arises from the base of the main axis and after growing aerially for some
time arch downwards to touch the ground. A lateral branch with short
internodes and each node bearing a rosette of leaves and a tuft of roots is
found in aquatic plants like Pistia and Eichhornia. In banana, pineapple
and Chrysanthemum, the lateral branches originate from the basal and
underground portion of the main stem, grow horizontally beneath the
soil and then come out obliquely upward giving rise to leafy shoots.

5.3 THE LEAF

The leaf is a lateral, generally flattened structure borne on the stem. It
develops at the node and bears a bud in its axil. The axillary bud later
develops into a branch. Leaves originate from shoot apical meristems and
are arranged in an acropetal order. They are the most important vegetative
organs for photosynthesis.
A typical leaf consists of three main parts: leaf base, petiole and lamina
(Figure 5.7 a). The leaf is attached to the stem by the leaf base and may

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5.8 SEMI-TECHNICAL DESCRIPTION OF A TYPICAL

FLOWERING PLANT
Various morphological features are used to describe a
flowering plant. The description has to be brief, in a simple
and scientific language and presented in a proper
sequence. The plant is described beginning with its habit,
vegetative characters – roots, stem and leaves and then
floral characters inflorescence and flower parts. After
describing various parts of plant, a floral diagram and a
floral formula are presented. The floral formula is
represented by some symbols. In the floral formula, Br
stands for bracteate K stands for calyx , C for corolla, P for
perianth, A for androecium and G for Gynoecium, G for
K2+2 C4 A2+4 G(2) superior ovary and G for inferior ovary, for male, for
⊕
female, for bisexual plants, ⊕ for actinomorphic and
Figure 5.20 Floral diagram with for zygomorphic nature of flower. Fusion is indicated by
floral formula enclosing the figure within bracket and adhesion by a line
drawn above the symbols of the floral parts. A floral
diagram provides information about the number of parts
of a flower, their arrangement and the relation they have
with one another (Figure 5.20). The position of the mother
axis with respect to the flower is represented by a dot on
the top of the floral diagram. Calyx, corolla, androecium
and gynoecium are drawn in successive whorls, calyx being
the outermost and the gynoecium being in the centre.
Floral formula also shows cohesion and adhesion within
parts of whorls and between whorls. The floral diagram
and floral formula in Figure 5.20 represents the mustard
plant (Family: Brassicaceae).

5.9 DESCRIPTION OF SOME IMPORTANT FAMILIES

5.9.1 Fabaceae
This family was earlier called Papilionoideae, a subfamily
of family Leguminosae. It is distributed all over the world
(Figure 5.21).
Vegetative Characters
Trees, shrubs, herbs; root with root nodules
Stem: erect or climber
Leaves: alternate, pinnately compound or simple; leaf base,
pulvinate; stipulate; venation reticulate.

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(b)

(c)

(e) (f)
(a) (d)

Figure 5.21 Pisum sativum (pea) plant : (a) Flowering twig (b) Flower (c) Petals
(d) Reproductive parts (e) L.S.carpel (f) Floral diagram

Floral characters
Inflorescence: racemose
Flower: bisexual, zygomorphic
Calyx: sepals five, gamosepalous; valvate/imbricate aestivation
Corolla: petals five, polypetalous, papilionaceous, consisting of a posterior
standard, two lateral wings, two anterior ones forming a keel (enclosing
stamens and pistil), vexillary aestivation
Androecium: ten, diadelphous, anther dithecous
Gynoecium: ovary superior, mono carpellary, unilocular with many
ovules, style single
Fruit: legume; seed: one to many, non-endospermic
Floral Formula: % K(5) C1+2+(2) A(9)+1 G1
Economic importance
Many plants belonging to the family are sources of pulses (gram, arhar,
sem, moong, soyabean; edible oil (soyabean, groundnut); dye (Indigofera);
fibres (sunhemp); fodder (Sesbania, Trifolium), ornamentals (lupin, sweet
pea); medicine (muliathi).

5.9.2 Solanaceae
It is a large family, commonly called as the ‘potato family’. It is widely
distributed in tropics, subtropics and even temperate zones (Figure 5.22).
Vegetative Characters
Plants mostly herbs, shrubs and rarely small trees
Stem: herbaceous rarely woody, aerial; erect, cylindrical, branched, solid

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(d)
(b)
(c)

(a)
(e) (f)

Figure 5.22 Solanum nigrum (makoi) plant : (a) Flowering twig (b) Flower
(c) L.S. of flower (d) Stamens (e) Carpel (f) Floral diagram

or hollow, hairy or glabrous, underground stem in potato (Solanum

tuberosum)
Leaves: alternate, simple, rarely pinnately compound, exstipulate;
venation reticulate
Floral Characters
Inflorescence : Solitary, axillary or cymose as in Solanum
Flower: bisexual, actinomorphic
Calyx: sepals five, united, persistent, valvate aestivation
Corolla: petals five, united; valvate aestivation
Androecium: stamens five, epipetalous
Gynoecium: bicarpellary obligately placed, syncarpous; ovary superior,
bilocular, placenta swollen with many ovules, axile
Fruits: berry or capsule
Seeds: many, endospermous
Floral Formula: ⊕
Economic Importance
Many plants belonging to this family are source of food (tomato, brinjal,
potato), spice (chilli); medicine (belladonna, ashwagandha); fumigatory
(tobacco); ornamentals (petunia).

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5.9.3 Liliaceae
Commonly called the ‘Lily family’ is a characteristic representative of
monocotyledonous plants. It is distributed world wide (Figure 5.23).
Vegetative characters: Perennial herbs with underground bulbs/corms/
rhizomes
Leaves mostly basal, alternate, linear, exstipulate with parallel venation
Floral characters
Inflorescence: solitary / cymose; often umbellate clusters
Flower: bisexual; actinomorphic
Perianth tepal six (3+3), often united into tube; valvate aestivation
Androecium: stamen six, 3+3, epitepalous
Gynoecium: tricarpellary, syncarpous, ovary superior, trilocular with
many ovules; axile placentation
Fruit: capsule, rarely berry
Seed: endospermous
Floral Formula: Br ⊕ P(3+3) A3+3 G(3)
Economic Importance
Many plants belonging to this family are good ornamentals (tulip,
Gloriosa), source of medicine (Aloe), vegetables (Asparagus), and
colchicine (Colchicum autumnale).

(b) (c)

(d)

(a)

Figure 5.23 Allium cepa (onion) plant : (a) Plant (b) Inflorescence (c) Flower
(d) Floral diagram

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