CHAPTER 5 - MORPHOLOGY OF FLOWERING PLANTS

• The underground part of the flowering plant is the root system while the portion
above the ground forms the shoot system.
• In majority of the dicotyledonous plants, the direct elongation of the radicle leads
to the formation of primary root which grows inside the soil.
• It bears lateral roots of several orders that are referred to as secondary, tertiary,
etc. roots.
• The primary roots and its branches constitute the tap root system.
• In monocotyledonous plants, the primary root is short lived and is replaced by a
large number of roots. These roots originate from the base of the stem and
constitute the fibrous root system.
• In some plants, like grass, Monstera and the banyan tree, roots arise from parts of
the plant other than the radicle and are called adventitious roots.
• The main functions of the root system are absorption of water and minerals from
the soil, providing a proper anchorage to the plant parts, storing reserve food
material and synthesis of plant growth regulators.
• The root is covered at the apex by a thimble-like structure called the root cap.
• 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 and delicate, thread-
like structures called root hairs.
• These root hairs absorb water and minerals from the soil.
• 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.
• Tap roots of carrot, turnip and adventitious roots of sweet potato, get swollen and
store food.
• The support roots of banyan trees are called prop roots.
• 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 get oxygen for respiration.
• The stem is the ascending part of the axis bearing branches, leaves, flowers and
fruits.
• 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.
• Some stems perform the function of storage of food, support, protection and of
vegetative propagation.
• 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.
• Some plants of arid regions modify their stems into flattened (Opuntia), or fleshy
cylindrical (Euphorbia) structures. They contain chlorophyll and carry 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.
• The leaf is a lateral, generally flattened structure borne on the stem.
• The axillary bud later develops into a branch. They are the most important
vegetative organs for photosynthesis.
• A typical leaf consists of three main parts: leaf base, petiole and lamina.
• The leaf is attached to the stem by the leaf base and may bear two lateral small
leaf like structures called stipules.
• In monocotyledons, the leaf base expands into a sheath covering the stem partially
or wholly.
• In some leguminous plants the leaf base may become swollen, which is called the
pulvinus.
• The petiole help hold the blade to light. Long thin flexible petioles allow leaf blades
to flutter in wind, thereby cooling the leaf and bringing fresh air to leaf surface.
• The lamina or the leaf blade is the green expanded part of the leaf with veins and
veinlets.
• There is, usually, a middle prominent vein, which is known as the midrib. Veins
provide rigidity to the leaf blade and act as channels of transport for water,
minerals and food materials. The shape, margin, apex, surface and extent of
incision of lamina varies in different leaves.
• The arrangement of veins and the veinlets in the lamina of leaf is termed as
venation.
• When the veinlets form a network, the venation is termed as reticulate.
• When the veins run parallel to each other within a lamina, the venation is termed
as parallel.
• Leaves of dicotyledonous plants generally possess reticulate venation, while
parallel venation is the characteristic of most monocotyledons.
• A leaf is said to be simple, when its lamina is entire or when incised, the incisions
do not touch the midrib.
• When the incisions of the lamina reach up to the midrib breaking it into a number
of leaflets, the leaf is called compound.
• The compound leaves may be of two types.
• In a pinnately compound leaf, a number of leaflets are present on a common axis,
the rachis, which represents the midrib of the leaf as in neem.
• In palmately compound leaves, the leaflets are attached at a common point, i.e.,
at the tip of petiole, as in silk cotton.
• Phyllotaxy is the pattern of arrangement of leaves on the stem or branch.
• This is usually of three types – alternate, opposite and whorled.
• In alternate type of phyllotaxy, a single leaf arises at each node in alternate
manner, as in China rose, mustard and sun flower plants.
• In opposite type, a pair of leaves arise at each node and lie opposite to each other
as in Calotropis and guava plants.
• If more than two leaves arise at a node and form a whorl, it is called whorled, as in
Alstonia.
• Leaves are often modified to perform functions other than photosynthesis. They
are converted into tendrils for climbing as in peas or into spines for defence as in
cacti.
• The fleshy leaves of onion and garlic store food.
• A flower is a modified shoot wherein the shoot apical meristem changes to floral
meristem.
• The arrangement of flowers on the floral axis is termed as inflorescence.
• two major types of inflorescences are defined – racemose and cymose.
• In racemose type of inflorescences the main axis continues to grow, the flowers
are borne laterally in an acropetal succession.
• In cymose type of inflorescence the main axis terminates in a flower, hence is
limited in growth. The flowers are borne in a basipetal order.
• The flower is the reproductive unit in the angiosperms. It is meant for sexual
reproduction.
• A typical flower has four different kinds of whorls arranged successively on the
swollen end of the stalk or pedicel, called thalamus or receptacle. These are calyx,
corolla, androecium and gynoecium.
• Calyx and corolla are accessory organs, while androecium and gynoecium are
reproductive organs.
• In some flowers like lily, the calyx and corolla are not distinct and are termed as
perianth.
• When a flower has both androecium and gynoecium, it is bisexual.
• A flower having either only stamens or only carpels is unisexual.
• In symmetry, the flower may be actinomorphic (radial symmetry) or zygomorphic
(bilateral symmetry).
• When a flower can be divided into two equal radial halves in any radial plane
passing through the centre, it is said to be actinomorphic, e.g., mustard, datura,
chilli.
• When it can be divided into two similar halves only in one particular vertical plane,
it is zygomorphic, e.g., pea, gulmohur, bean, Cassia.
• A flower is asymmetric (irregular) if it cannot be divided into two similar halves by
any vertical plane passing through the centre, as in canna.
• A flower may be trimerous, tetramerous or pentamerous when the floral
appendages are in multiple of 3, 4 or 5, respectively.
• Flowers with bracts-reduced leaf found at the base of the pedicel- are called
bracteate and those without bracts, ebracteate.
• Based on the position of calyx, corolla and androecium in respect of the ovary on
thalamus, the flowers are described as hypogynous, perigynous and epigynous.
• In the hypogynous flower the gynoecium occupies the highest position while the
other parts are situated below it. The ovary in such flowers is said to be superior,
e.g., mustard, China rose and brinjal.
• If gynoecium is situated in the centre and other parts of the flower are located on
the rim of the thalamus almost at the same level, it is called perigynous. The ovary
here is said to be half inferior, e.g., plum, rose, peach.
• In epigynous flowers, the margin of thalamus grows upward enclosing the ovary
completely and getting fused with it, the other parts of flower arise above the
ovary. Hence, the ovary is said to be inferior as in flowers of guava and cucumber,
and the ray florets of sunflower.
• The calyx is the outermost whorl of the flower and the members are called 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).
• Corolla is composed of petals. Petals are usually brightly coloured to attract insects
for pollination. Like calyx, corolla may also be gamopetalous (petals united) or
polypetalous (petals free).
• Corolla may be tubular, bell-shaped, funnel-shaped or wheel-shaped.
• Aestivation: The mode of arrangement of sepals or petals in floral bud with respect
to the other members of the same whorl is known as aestivation. The main types
of aestivation are valvate, twisted, imbricate and vexillar.
• When sepals or petals in a whorl just touch one another at the margin, without
overlapping, as in Calotropis, it is said to be valvate.
• If one margin of the appendage overlaps that of the next one and so on as in China
rose, lady’s finger and cotton, it is called twisted.
• If the margins of sepals or petals overlap one another but not in any particular
direction as in Cassia and gulmohur, the aestivation is called imbricate.
• In pea and 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 type of aestivation is known as vexillary or papilionaceous.
• Androecium is composed of stamens.
• Each stamen which represents the male reproductive organ consists of a stalk or a
filament and an anther.
• The pollen grains are produced in pollen-sacs.
• A sterile stamen is called staminode.
• When stamens are attached to the petals, they are epipetalous as in brinjal, or
epiphyllous when attached to the perianth as in the flowers of lily.
• The stamens in a flower may either remain free (polyandrous) or may be united in
varying degrees.
• The stamens may be united into one bunch or one bundle (monoadelphous) as in
china rose, or two bundles (diadelphous) as in pea, or into more than two bundles
(polyadelphous) as in citrus.
• Gynoecium is the female reproductive part of the flower and is made up of one or
more carpels. A carpel consists of three parts namely stigma, style and ovary.
• Ovary is the enlarged basal part, on which lies the elongated tube, the style. The
style connects the ovary to the stigma. The stigma is usually at the tip of the style
and is the receptive surface for pollen grains.
• Each ovary bears one or more ovules attached to a flattened, cushion-like placenta.
When more than one carpel is present, they may be free (as in lotus and rose) and
are called apocarpous. They are termed syncarpous when carpels are fused, as in
mustard and tomato.
• After fertilisation, the ovules develop into seeds and the ovary matures into a fruit.
• Placentation: The arrangement of ovules within the ovary is known as
placentation.
• The placentation are of different types namely, marginal, axile, parietal, basal,
central and free central.
• In marginal placentation the placenta forms a ridge along the ventral suture of the
ovary and the ovules are borne on this ridge forming two rows, as in pea.
• When the placenta is axial and the ovules are attached to it in a multilocular ovary,
the placentaion is said to be axile, as in china rose, tomato and lemon.
• In parietal placentation, 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.
• When the ovules are borne on central axis and septa are absent, as in Dianthus and
Primrose the placentation is called free central.
• In basal placentation, the placenta develops at the base of ovary and a single ovule
is attached to it, as in sunflower, marigold.
• The fruit is a characteristic feature of the flowering plants.
• If a fruit is formed without fertilisation of the ovary, it is called a parthenocarpic
fruit.
• Generally, the fruit consists of a wall or pericarp and seeds.
• The pericarp may be dry or fleshy.
• When pericarp is thick and fleshy, it is differentiated into the outer epicarp, the
middle mesocarp and the inner endocarp.
• In mango the pericarp is well differentiated into an outer thin epicarp, a middle
fleshy edible mesocarp and an inner stony hard endocarp. In coconut which is also
a drupe, the mesocarp is fibrous.
• The ovules after fertilisation, develop into seeds. A seed is made up of a seed coat
and an embryo.
• The embryo is made up of a radicle, an embryonal axis and one (as in wheat,
maize) or two cotyledons (as in gram and pea).
• The outermost covering of a seed is the seed coat. The seed coat has two layers,
the outer testa and the 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.
• 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 formed as a result of double
fertilisation, is a food storing tissue and called endospermic seeds.
• In plants such as bean, gram and pea, the endosperm is not present in mature
seeds and such seeds are called non-endospermous.
• Generally, monocotyledonous seeds are endospermic but some as in orchids are
non-endospermic.
• In the seeds of cereals such as maize the seed coat is membranous and generally
fused with the fruit wall.
• 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 and radicle are enclosed in sheaths which are called coleoptile and
coleorhiza respectively.
• Various morphological features are used to describe a flowering plant.
• 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, for superior ovary and for

inferior ovary, for male, for female, for bisexual plants, for
actinomorphic and for zygomorphic nature of flower.
• A floral diagram provides information about the number of parts of a flower, their
arrangement and the relation they have with one another.
• 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.

DESCRIPTION OF SOME IMPORTANT FAMILIES

1) Fabaceae
• This family was earlier called Papilionoideae, a subfamily of family Leguminosae.
• 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.
• 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
• 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).
2) Solanaceae
• It is a large family, commonly called as the ‘potato family’. It is widely distributed in
tropics, subtropics and even temperate zones.
• Vegetative Characters- Plants mostly herbs, shrubs and rarely small trees
Stem herbaceous rarely woody, aerial; erect, cylindrical, branched,
solid 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).
3) Liliaceae
• Commonly called the ‘Lily family’ is a characteristic representative of
monocotyledonous plants. It is distributed worldwide.
• 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
• Economic Importance - Many plants belonging to this family are good ornamentals
(tulip Gloriosa), source of medicine (Aloe), vegetables (Asparagus), and colchicine
(Colchicum autumnale).
 SUMMARY
• Root system is either tap root or fibrous.
• Generally, dicotyledonous plants have tap roots while monocotyledonous plants
have fibrous roots.
• The roots in some plants get modified for storage of food, mechanical support and
respiration.
• The shoot system is differentiated into stem, leaves, flowers and fruits.
• The morphological features of stems like the presence of nodes and internodes,
multicellular hair and positively phototropic nature help to differentiate the stems
from roots.
• Stems also get modified to perform diverse functions such as storage of food,
vegetative propagation and protection under different conditions.
• Leaf is a lateral outgrowth of stem developed exogeneously at the node. These are
green in colour to perform the function of photosynthesis. Leaves exhibit marked
variations in their shape, size, margin, apex and extent of incisions of leaf blade
(lamina).
• Like other parts of plants, the leaves also get modified into other structures such as
tendrils, spines for climbing and protection respectively.
• The flower is a modified shoot, meant for sexual reproduction. The flowers are
arranged in different types of inflorescences. They exhibit enormous variation in
structure, symmetry, position of ovary in relation to other parts, arrangement of
petals, sepals, ovules etc. After fertilisation, the ovary is modified into fruits and
ovules into seeds. Seeds either may be monocotyledonous or dicotyledonous.
• The floral characteristics form the basis of classification and identification of
flowering plants.
• This can be illustrated through semi-technical descriptions of families. Hence, a
flowering plant is described in a definite sequence by using scientific terms. The
floral features are represented in the summarised form as floral diagrams and
floral formula.