CHAPTER

05
morphology of
flowering plants
 • Morphology is the study of external forms of organisms.
• A flowering plant (Angiosperm) has 2 parts: Root system (underground part)
& Shoot system (portion above the ground).

THE ROOT
• It is the underground part formed from radicle of embryo.
• Root systems are 3 types:
o Tap root system: It consists of primary roots (tap root) and its branches
(lateral roots such as secondary roots, tertiary roots).
Seen in dicots. Primary root is elongated from radicle. E.g. Mustard plant.
o Fibrous root system: In monocots, primary root is short livedand is
replaced by many roots. They originate from the
base of stem to form fibrous root system. E.g. Wheat.
o Adventitious root system: Roots that arise from parts other than radicle.
E.g. Grass, Monstera and banyan tree.

1. Regions of the Root

o Root cap: It is the covering at the apex of root. It protects the tender apex of
the root.
o Region of meristematic activity: Seen above the root cap. Here, the cells are very
small, thin-walled and with dense protoplasm. They
divide repeatedly.
o Region of elongation: Region just above the meristematic region. Here, cells undergo
rapid elongation and enlargement. Helps in growth of the root
in length.
o Region of maturation: It is proximal to elongation zone. Here, the cells differentiate
and mature.
o Root hairs: Very fine, delicate, thread-like structures formed from epidermal cells in
region behind region of elongation. They absorb water and minerals from
the soil.

2. Modifications of Root
In some plants, roots are modified to perform functions other than absorption and
conduction. E.g.
o Swollen roots for food storage: E.g. Tap roots of carrot, turnips and adventitious roots
of sweet potato.
o Prop roots: Hanging structures that support banyan tree.
o Stilt roots: The supporting roots coming out of the lower nodes of the stem. E.g. maize
& sugarcane.
o Pneumatophores: The roots that come out of the ground and grow vertically upwards to
get oxygen for respiration. E.g. Rhizophora growing in swampy areas.

3. Functions of root
• Absorption of water and minerals from the soil.
• Provide a proper anchorage to the plant parts.
• Storage of reserve food material.
• Synthesis of plant growth regulators.

THE STEM
• It is the ascending part of the axis that develops from the plumule of the embryo
of a germinating seed.
• It bears branches, leaves, flowers, fruits, buds (terminal or axillary), nodes and
internodes.
• Nodes are the regions of the stem where leaves are born.
Internodes are the portions between two nodes.
• Young stem is generally green and later often become woody and dark brown.

1. Functions of stem:
• Spreading out branches bearing leaves, flowers and fruits.
• It conducts water, minerals and photosynthates.
• Food storage, support, protection & vegetative propagation.

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 2. Modifications of Stem
o For food storage: E.g. underground stems of potato, ginger, turmeric,
zaminkand, Colocasia etc. They also act as organs of
perennation to tide over conditions unfavorable for growth.
o Stem tendrils: Slender and spirally coiled structures formed from axillary
buds. They help plants to climb. E.g. Gourds (cucumber,
pumpkins, watermelon) & grapevines.�
o Thorns: Woody, straight and pointed structures developed from axillary
buds. They protect plants from browsing animals. E.g. Citrus,
Bougainvillea.
o Phylloclade: It is a green, flattened or fleshy cylindrical stem containing
chlorophyll for photosynthesis. Found in some plants of arid regions.
E.g. Opuntia (flattened stem), Euphorbia (cylindrical stem).
o Stolon: Slender lateral branch that arises from the base of the main axis and
after growing aerially for some time arch downwards to touch the
ground. E.g. mint & jasmine.
o Offset: It is a lateral branch with short internodes and each node bearing a
rosette of leaves and a tuft of roots . E.g. aquatic plants like Pistia and
Eichhornia.
o Sucker: The lateral branches that originate from the basal underground part of
the main stem. It grows horizontally beneath the soil and come out
obliquely upward giving rise to leafy shoots. E.g. Banana, Pineapple & Chrysanthemum.
Underground stems of grass, strawberry etc. spread to new niches. When older parts
die, new plants are formed.

THE LEAF
• It is a lateral, 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 important vegetative organs for photosynthesis.

A typical leaf has 3 main parts:

o Leaf base: With this, the leaf is attached to stem. It may bear two lateral
small leaf-like structures called stipules. In monocots, the leaf
base expands into a sheath covering the stem partially or wholly. In some
leguminous plants, the leaf base may be swollen. It is called pulvinus.
o Petiole: It helps to hold the leaf blade to light. Long thin flexible petioles
allow leaf blades to flutter in wind, thereby cooling leaf and
bringing fresh air to leaf surface.
o Lamina (leaf blade): The green expanded part with veins & veinlets. The
middle prominent vein is called midrib. Veins provide rigidity
to lamina and act as channels of transport for water, minerals & food materials

1. Venation
• It is the arrangement of veins and veinlets in leaf lamina.
• It is 2 types:
o Reticulate venation: Here, the veinlets form a network. It is seen in dicotyledons.
o Parallel venation: Here, the veins run parallel to each other within a lamina. It is
seen in monocotyledons.

2. Types of Leaves
• Simple leaf: Here, leaf lamina is entire or when incised, the incisions do not touch the
midrib.
• Compound leaf: Here, the incisions of the lamina reach up to the midrib breaking it
into several leaflets.
A bud is seen in the axil of petiole in simple & compound leaves, but not in the axil of
leaflets of the compound leaf. The compound leaves are 2 types.
o Pinnately compound leaf: In this, many leaflets are present on a common axis, the
rachis, which represents the midrib of the leaf. E.g. neem.
o Palmately compound leaf: In this, leaflets are attached at a common point (at the
tip of petiole). E.g. silk cotton.

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 3. Phyllotaxy
• It is the pattern of arrangement of leaves on the stem or branch.
It is 3 types:
o Alternate: In this, a single leaf arises at each node in alternate manner.
E.g. China rose, mustard & sunflower.
o Opposite: In this, a pair of leaves arise at each node and lie opposite to
each other. E.g. Calotropis and guava.
o Whorled: In this, more than two leaves arise at a node and form a
whorl. E.g. Alstonia.

4. Modifications of Leaves
• Leaves are modified to perform functions other than photosynthesis. E.g.
o Tendrils: For climbing. E.g. peas.
o Spines: For defense. E.g. cacti.
o Fleshy leaves: To store food. E.g. onion and garlic.
• In plants such as Australian acacia, the leaves are small and short-lived.
The petioles in these plants expand, become green and synthesise food.
• Leaves of some insectivorous plants (e.g. pitcher plant, Venus-fly trap) are
also modified leaves.

THE FLOWER AND THE INFLORESCENCE

• A flower is a modified shoot wherein the shoot apical meristem changes to
floral meristem.
• Internodes do not elongate and the axis gets condensed.
• The apex produces different kinds of floral appendages laterally at successive
nodes instead of leaves.
• When a shoot tip transforms into a flower, it is solitary.
• The arrangement of cluster of flowers on the floral axis is called inflorescence.
• Based on whether the apex gets converted into a flower or continues to grow,
inflorescences are 2 types: Racemose and Cymose.
o Racemose: In this, the main axis continues to grow. Flowers are borne
laterally in an acropetal succession.
o Cymose: In this, main axis terminates in a flower, hence is limited in growth.
Flowers are borne in a basipetal order.

1. THE FLOWER
• It is the reproductive unit in the angiosperms.
• It is meant for sexual reproduction.
• A flower has a stalk (pedicel). Its swollen end is called thalamus (receptacle).
• Reduced leaf found at the base of the pedicel is called bracts. Flowers with
bracts are called bracteate and those without bracts, ebracteate.
• A typical flower has 4 kinds of whorls arranged on thalamus- calyx, corolla,
androecium & gynoecium.
• Calyx & corolla are accessory organs, while androecium and gynoecium are
reproductive organs.
• In flowers like lily, the calyx and corolla are not distinct. It is termed as perianth.
• When a flower has both androecium and gynoecium, it is bisexual. A flower having
either only androecium or only gynoecium is unisexual.

Based on symmetry, flowers are 3 types:

o Actinomorphic (radial symmetry): Here, a flower can be divided into 2 equal
radial halves in any radial plane passing through
the centre. E.g. mustard, datura, chilli.
o Zygomorphic (bilateral symmetry): Here, a flower can be divided into two similar
halves only in a particular vertical plane.
E.g. pea, gulmohur, bean, Cassia.
o Asymmetric (irregular): Here, a flower cannot be divided into two similar halves by
any vertical plane passing through the centre. E.g. canna.

Based on number of floral appendages, flowers are classified as follows:

o Trimerous: Floral appendages are multiple of 3.
o Tetramerous: Floral appendages are multiple of 4.
o Pentamerous: Floral appendages are multiple of 5.

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 Based on the position of calyx, corolla and androecium in
respect of the ovary on thalamus, the flowers are 3 types:
o Hypogynous: Here, gynoecium occupies the highest position while other
parts are situated below it. The ovary is superior.
E.g. mustard, China rose & brinjal.
o Perigynous: Here, gynoecium is situated in the centre and other parts
are located on the rim of the thalamus at the same level.
Ovary is half inferior. E.g. plum, rose, peach.
o Epigynous: Here, the margin of thalamus grows upward enclosing the
ovary completely and getting fused with it. Other parts arise
above the ovary. The ovary is inferior. E.g. Guava, cucumber,
ray florets of sunflower

2. Parts of a Flower
a) Calyx
• It is the outermost whorl of flower. It is made of sepals.
• Generally, sepals are green, leaf like and protect the flower in the bud stage.
• The calyx may be gamosepalous (sepals united) or polysepalous (sepals free).

b)Corolla
• It is the whorl inner to calyx. It is composed of petals.
• Petals have bright colour to attract insects for pollination.
• Corolla may be gamopetalous (petals united) or polypetalous (petals free).
• Shape and colour of corolla vary in plants. Corolla may be tubular, bell-shaped,
funnel-shaped or wheel-shaped.
• The mode of arrangement of sepals and petals in floral bud is called aestivation.
3. Types of aestivation:
o Valvate: Sepals or petals in a whorl just touch one another at the margin,
without overlapping. E.g. Calotropis.
o Twisted: One margin of the appendage overlaps that ofthe next one and
so on. E.g. China rose, lady’s finger & cotton.
o Imbricate: Margins of sepals or petals overlap one another but not in any
particular direction. E.g. Cassia & gulmohur.
o Vexillary (papilionaceous): In pea & bean flowers, there are five petals; the largest
(standard) overlaps the two lateral petals (wings) which
in turn overlap the two smallest anterior petals (keel). This is called vexillary.

c) Androecium
• The male reproductive part composed of stamens.
• Each stamen represents the male reproductive organ. It consists of a stalk
(filament) and an anther.
• Each anther is usually bilobed. Each lobe has 2 chambers, the pollen-sacs.
• The pollen grains are produced in pollen-sacs.
• A sterile stamen is called staminode.
• When stamens are attached to petals, they are epipetalous.
E.g. brinjal. When stamens are attached to perianth they are epiphyllous. E.g. lily
• If the stamens are free, it is called polyandrous. If they are united it is called
synandrous. It is many types:
o Monoadelphous: Stamens are united into one bunch or one bundle. E.g. China rose.
o Diadelphous: Stamens are united into two bundles. E.g. pea.
o Polyadelphous: Stamens are united into more than two bundles. E.g. citrus.
• There may be a variation in the length of filaments within a flower.
E.g. Salvia and mustard.

d) Gynoecium (Pistil)
• The female reproductive part made up of one or more carpels.
A carpel has 3 parts:
o Stigma: It is the receptive surface for pollen grains. It is usually at the tip
of the style.
o Style: An elongated tube that connects ovary to stigma.
o Ovary: It is the enlarged basal part on which the style lies. Each ovary
bears one or more ovules attached to a flattened, cushion-like
placenta. Polycarpellary pistils (pistil with many carpels) are 2 types:
o Apocarpous: Carpels are free. E.g. lotus and rose.
o Syncarpous: Carpels are fused. E.g. mustard and tomato.

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 • Placentation: It is the arrangement of ovules on the placenta within the
ovary. It is many types :
o Marginal: Here, the placenta forms a ridge along the ventral suture of
the ovary and the ovules are borne on this ridge forming two
rows. E.g. pea.
o Axile: Here, the placenta is axial and the ovules are attached to it in a
multilocular ovary. E.g. China rose, tomato and lemon.
o Parietal: Here, the ovules develop on the inner wall of the ovary or on
peripheral part. Ovary is one�chambered but it becomes two-
chambered due to the formation of the false septum. E.g. mustard and
Argemone.
o Basal: Here, placenta develops at the base of ovary and a single ovule
is attached to it. E.g. sunflower, marigold.
o Free central: Here, ovules are borne on central axis and septa are
absent. E.g. Dianthus and Primrose.
After fertilisation, the ovules develop into seeds and the ovary matures
into a fruit.

THE FRUIT
• It is a ripened ovary developed after fertilisation.
• It is a characteristic feature of the flowering plants.
• If a fruit is formed without fertilisation of the ovary, it is called a parthenocarpic
fruit.
• In mango & coconut, fruit is called a drupe. They are one seeded and develop
from monocarpellary superior ovaries.
• A fruit consists of
o Pericarp (fruit wall): It may be dry or fleshy. When pericarp is thick and
fleshy, it is differentiated into outer epicarp, middle
mesocarp and inner endocarp.
o Seeds: In mango, the pericarp is well differentiated into thin epicarp, fleshy
edible mesocarp and stony hard endocarp. In coconut, the mesocarp is fibrous.

THE SEED
• It is the mature ovule developed after fertilisation.
• A seed is made up of a seed coat and an embryo.
• Embryo is made up of a radicle, an embryonal axis and one (e.g. wheat, maize) or
2 cotyledons (e.g. gram & pea).

1. Structure of a Dicotyledonous Seed

• The outermost covering of a seed is the seed coat.
• Seed coat has 2 layers: outer testa and inner tegmen.
• The hilum is a scar on the seed coat through which the developing seeds were
attached to the fruit.
• Above the hilum is a small pore called the micropyle.
• Within the seed coat is the embryo, consisting of an embryonal axis and
two cotyledons.
• The cotyledons are often fleshy and full of reserve food materials. At the
two ends of the embryonal axis are present the radicle and the plumule.
• In some seeds such as castor, the endosperm is formed due to double
fertilisation. It is a food storing tissue.
• In plants such as bean, gram and pea, the seeds are non- endospermous
(endosperm is not seen in mature seeds).

2. Structure of Monocotyledonous Seed

• Generally, monocot seeds are endospermic but some are non-endospermic
(e.g. orchids).
• In cereals such as maize, the seed coat is membranous and generally fused
with the fruit wall.
• The endosperm is bulky and stores food.
• The outer covering of endosperm separates the embryo by a proteinous layer
called aleurone layer.
• The embryo is small and situated in a groove at one end of the endosperm. It
consists of one large and shield shaped cotyledon known as scutellum and a
short axis with a plumule and a radicle.
• The plumule is protected in a sheath called coleoptile and radicle is protected in
a sheath called coleorhiza.

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 SEMITECHNICAL DESCRIPTION OF A
TYPICAL FLOWERING PLANT
• The plant is described beginning with its habit, vegetative characters
and then floral characters.
• Then a floral diagram and a floral formula are presented.
• Floral formula is represented by some symbols. They are

C (corolla) K (calyx)
G (Gynoecium) A (androecium)
Br (bracteates) (inferior ovary)
P (perianth) (female)
G (superior ovary) (bisexual�
(male)
(actinomorphic) .(zygomorphic)
• Fusion is indicated by enclosing the figure within bracket and
adhesion by a line drawn above the symbols of the floral parts.
• A floral diagram gives information about the number of�parts of a
flower, their arrangement and relation.
• Floral formula also shows cohesion and adhesion within parts of
whorls and in between whorls.

SOME IMPORTANT FAMILIES

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

Floral characters:
o Inflorescence: racemose.
o Flower: bisexual, zygomorphic.
o Calyx: sepals five, gamosepalous; imbricate aestivation.
o 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.
o Androecium: ten, diadelphous, anther dithecous.
o Gynoecium: ovary superior, mono carpellary, unilocular with many ovules,
style single.
o Fruit: legume; seed: one to many, non-endospermic
o Floral Formula: K(5) C1+2+(2) A(9)+1 G
o Pulses: E.g. gram, arhar, sem, moong, soyabean
o Edible oil: E.g. soyabean, groundnut
o Dye: E.g. Indigofera
o Fibres: E.g. sun hemp
o Fodder: E.g. Sesbania, Trifolium
o Ornamentals: E.g. lupin, sweet pea
o Medicine: E.g. muliathi

2. Solanaceae (Potato family)

• It is a large family. It is widely distributed in tropics, subtropics and even
temperate zones.

Vegetative Characters
o Plants mostly, herbs, shrubs and small trees.
o Stem: herbaceous rarely woody, aerial; erect, cylindrical, branched, solid or
hollow, hairy or glabrous, underground stem in potato (Solanum tuberosum).
o Leaves: alternate, simple, rarely pinnately compound, exstipulate; venation reticulate.

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 Floral Characters
o Inflorescence: Solitary, axillary or cymose as in Solanum
o Flower: bisexual, actinomorphic
o mCalyx: sepals five, united, persistent, valvate aestivation
o Corolla: petals five, united; valvate aestivation
o Androecium: stamens five, epipetalous
o Gynoecium: bicarpellary, syncarpous; ovary superior, bilocular,
placenta swollen with many ovules
o Fruits: berry or capsule
o Seeds: many, endospermous
o Floral Formula: K(5) C(5) A(5) G(2)

Economic Importance:
o Food: E.g. tomato, brinjal, potato
o Spice: E.g. chilli
o Medicine: E.g. belladonna, ashwagandha.
o Fumigatory: E.g. tobacco.
o Ornamentals: E.g. petunia.

3. Lilaceae (Lily family)

• A characteristic representative of monocotyledonous plants. It is
distributed worldwide.

Vegetative characters:
o Perennial herbs with underground bulbs/corms/ rhizomes
o Leaves mostly basal, alternate, linear, exstipulate with parallel venation

Floral characters:
o Inflorescence: solitary / cymose; often umbellate clusters
o Flower: bisexual; actinomorphic
o Perianth tepal six (3+3), often united into tube; valvate aestivation
o Androcium: stamen six, (3+3)
o Gynoecium: tricarpellary, syncarpous, ovary superior, trilocular with
many ovules; axile placentation
o Fruit: capsule, rarely berry
o Seed: endospermous
o Floral Formula: P3+3 A3+3 G (3)�

Economic Importance:
o Ornamentals: E.g. tulip, Gloriosa
o Medicine: E.g. Aloe
o Vegetables: E.g. Asparagus
o Colchicines: E.g. Colchicum autumnale

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