CHAPTER 5

MORPHOLOGY OF FLOWERING PLANTS

1. What is meant by modification of root? What type of modification of root is
found in the:

(a) Banyan tree

(b) Turnip
(c) Mangrove trees

Answer. Roots of some plants change their shape and structure and become
modified to perform certain functions other than absorption and conduction of water
and minerals. It is called modification of roots. Roots are modified for support,
storage of food and respiration, etc.
(a) Root modification in banyan tree : The banyan tree (Ficus benghalensis) has
massive pillar-like adventitious roots arising from the aerial part of the stem. These
roots grow towards the ground and provide support to the tree. Such roots are called
prop roots.
(b) Root modification in turnip : The modification of root found in turnip is napiform
for food storage. The upper portion of these fleshy roots is inflated or swollen which
tapers towards the lower end.
(c) Root modification in mangrove trees : The roots of mangrove plants grow
vertically upwards from the soil for the absorption of oxygen from the atmosphere as
the soil is poorly aerated. These types of roots are called pneumatophores.

2.Justify the following statements on the basis of external features:

(i) Underground parts of a plant are not always roots.
(ii) Flower is a modified shoot.

Answer.(i) There are not always roots for underground plant because sometimes the
stem also becomes underground and gets modified into various forms to complete
several functions of storage, vegetative propagation, perennation, etc. Underground
modifications of stems are tuber, rhizome, corm and bulb. The underground stems
can be distinguished from roots externally by the presence of nodes and internodes,
axillary buds, scale leaves etc. and by absence of root cap and root hairs.
(ii) During the flowering season, the apical meristem gives rise to the floral meristem.
The axis of the stem gets condensed, while the internodes lie near each other.
Instead of leaves, various floral appendages arise from the node. Therefore, it can
be said that the flower is a modified shoot.

3. How is a pinnately compound leaf different from a palmately compound

leaf?
Answer.

Pinnately compound leaf Palmately compound leaf

The leaflets are attached to the common axis, called The leaflets are attached at a common
rachis. point on the leaf stalk.
Examples include neem and Cassia fistula( also Examples include silk cotton (Bombax )
called golden shower plant) and Cannabis.
4.Explain with suitable examples the different types of phyllotaxy.

Answer. Phyllotaxy can be defined as the pattern of arrangement of leaves on the

stem or branch. It is mainly 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 sunflower plants. In opposite type, a pair of leaves arises
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 phyllotaxy
as in Alstonia.

5. Define the following terms:

(a) aestivation (b) placentation
(c) actinomorphic (d) zygomorphic
(e) superior ovary (f) perigynous flower (g) epipetalous stamen.

Answer. (a) Aestivation : The mode of arrangement of accessory floral organs

(sepals and petals) in relation to one another in floral bud is known as aestivation.
The main type of aestivation are valvate, twisted, imbricate, and vexillary.
(b) Placentation : The arrangement of ovules within the ovary is known as
placentation. It is primarily of five types, namely marginal, basal, parietal, axile, and
free central.
(c) Actinomorphic : When flower can be divided into equal radial halves in any
radial plane passing through the centre, it is said to be actinomorphic, e.g., mustard,
Datura etc.
(d) Zygomorphic : When a flower can be divided into two similar halves by a single
vertical plane, it is said to be zygomorphic, e.g., pea, gulmohar, bean, Cassia.
(e) Superior ovary : In 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, brinjal.
(f) Perigynous flower: In perigynous flowers, the gynoecium is present in the centre
and the rest of the floral parts are arranged at the rim of the thalamus at the same
level. Examples include plum and rose.
(g) Epipetalous stamen : When stamens are attached to the petals, they are called
epipetalous stamens e.g., brinjal.

6.Differentiate between
(a) Racemose and cymose inflorescence
(b) Fibrous root and adventitious root

Answer.(a) Differences between racemose and cymose inflorescence are as

follows:

Racemose Inflorescence Cymose Inflorescence

The main axis continues to grow The main axis terminates in a flower.
Growth is not limited. Growth is limited
The flowers are borne in an acropetal
Flowers are borne in a basipetal succession
succession
The grouping of flowers is less common and The grouping of flowers is more common and
arrangement of flowers in a group is arrangement of flowers in a group is
centripetal centrifugal
(b) Differences between fibrous and adventitious roots are as follows :

Fibrous root Adventitious root

In monocots, the primary root which
develops from the radicle of the seed is short- These roots arise from any part of the plant
lived and is replaced by a large number of other than the radicle of seeds.
roots arising from the base of the stem.
It is found in banyan, Monstera, and other
It is found in wheat and other cereals.
plants.
7. Draw the labelled diagram of the following:
(i) Gram seed
(ii) V.S. of maize seed

Answer.
(a)

(b)

8. Describe modifications of stem with suitable examples.

Answer. The modifications of Stem with suitable examples are:

→ Food Storage: Stems are modified to perform different functions.
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.

Tendrils: 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.

→ Thorns: 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 fleshycylindrical (Euphorbia) structures. They
contain chlorophyll and carry out photosynthesis.

→ Vegetative Reproduction: 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.

9. Take one flower each of families Fabaceae and Solanaceae and write its semi-
technical description. Also draw their floral diagrams after studying them.

Answer. → Family Fabaceae (Pea)

Fabaceae (earlier called Papilionaceae) is a sub-family of the Leguminoseae family.

• Vegetative features:
Habit: Pinnately compound, alternately arranged with leaf tendrils with the pulvinus
present at the leaf base along folacious stipules.
Root: Tap root system with root nodules.

• Floral features:
Inflorescence: Racemose, generally axial than terminal
Flower: Zygomorphic and bisexual flowers are found
Calyx: It contains five sepals which are gamosepalous while aestivation is imbricate.
Corolla: It contains five petals (polypetalous) with vexillary aestivation.
Androecium: It consists of ten anthers that are diadelphous with dithecous anthers.
Gynoecium: Monocarpellary superior ovary which is unilocular with marginal
placentation.
Fruit: Legume pod with non-endospermic seeds
Floral formula:
Economic importance: Peas are used as vegetables for making various culinary
preparations.

→ Flowers of Solanum nigrum

Family Solanaceae

• Vegetative features:
Habit: Erect, herbaceous plant
Leaves: Simple, exstipulate leaves with reticulate venation
Stem: Erect stem with numerous branches.

• Floral features:
Inflorescence: Solitary and axillary
Flowers: Actinomorphic, bisexual flowers
Calyx: Calyx is composed of five sepals that are united and persistent. Aestivation is
valvate.
Corolla: Corolla consists of five united petals with valvate aestivation.
Androecium: It consists of five epipetalous stamens.
Gynoecium: It consists of bicarpellary syncarpous superior ovary with axile
placentation.
Fruits: Berry
Seeds: Numerous, endospermous

Floral formula:
Economic importance: Used for medicinal purposes.
10. Describe the various types of placentations found in flowering plants.

Answer. 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.

The various types of placentations found in flowering plants are:

→ Marginal placentation: The ovary in which the placenta forms a ridge along the
ventral suture of the ovary and the ovules develop on two separate rows is known to
have marginal placentation. This type of placentation is found in peas.

→ Parietal placentation: When the ovules develop on the inner walls of the ovary,
the ovary is said to have parietal placentation.

→ Axile placentation: In axile placentation, the placenta is axial and ovules are
attached to it. Examples include China rose, lemon, and tomato.

→ Basal placentation: The ovary in which the placenta develops from its base and
a single ovule is found attached to the base is said to have basal placentation. It is
found in marigold and sunflower.
→ Free central placentation: In free central placentation, the ovules develop on the
central axis while the septa are absent. This type of placentation is found in Dianthus
and primrose.

11. What is a flower? Describe the parts of a typical angiosperm flower?

Answer. The flower is the reproductive unit in the angiosperms. It is meant for
sexual reproduction. A flower has four different parts i.e., the calyx, corolla,
androecium, and gynoecium. Androecium and gynoecium represent the male and
female reproductive organs of a flower respectively. Parts of flower are:

→ The calyx: 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. When the sepals of a flower are free, they are called polysepalous, while
fused sepals of a flower are called gamosepalous.

→ Corolla: Corolla is composed of petals. Petals are usually brightly coloured to

attract insects for pollination. When the petals are free, they are called polypetalous,
while fused petals are called gamopetalous. Corolla may be tubular, bell-shaped,
funnel-shaped or wheel-shaped.

→ The androecium or the stamen is the male reproductive part of a flower. It

consists of two parts, the filament and the bilobed anther. The bilobed anther is the
site for meiosis and the generation of pollen grains.

→ Gynoecium represents the female reproductive part of a flower. It consists of an

ovary. The ovary is connected by a long tube (called style) to the stigma. The ovary
bears numerous ovules attached to the placenta.

12. How do the various leaf modifications help plants?

Answer.
Leaves are often modified to perform functions other than photosynthesis. These
are:
→ Tendrils: The leaves of a pea plant are modified into tendrils that help the plant in
climbing.
→ Spines: The leaves in cactus are modified into sharp spines that act as an organ
of defense.
→Phyllode: The leaves of some Australian acacia are short-lived and soon replaced
by flattened, green structures called phyllodes that arise from the petiole of the
leaves. The petioles in these plants synthesize food.
→ Pitcher: The leaves of the pitcher plant are modified into pitcher-like structures,
which contain digestive juices and help in trapping and digesting insects.

13. Define the term inflorescence. Explain the basis for the different types of
inflorescence in flowering plants.

Answer. Inflorescence is the manner in which the flowers are arranged on the
flowering axis. During the flowering season, the vegetative apex of the stem gets
converted into a floral meristem. Depending on

whether the apex gets converted into a flower or continues to grow, two major types
of inflorescences are defined – racemose and cymose.

In racemose inflorescence, the floral axis continues to grow and produces flowers
laterally while in cymose inflorescence, the main axis terminates into a flower.
Hence, it is limited in growth.

14. Write the floral formula of an actinomorphic bisexual, hypogynous flower with five
united sepals, five free petals, five free stamens and two united carpals with superior
ovary and axile placentation.

Answer. The floral formula of the described flower is

as
Actinomorphic flowers are represented by the symbol

A bisexual flower is indicated by

The calyx contains five united sepals which can be represented as K(5).
The corolla consists of five free petals and it represented as C5.
The androecium consists of five free stamens and is represented by A5.
The gynoecium consists of a superior ovary with two united carpels and axile
placentations, which can be represented as G2

15. Describe the arrangement of floral members in relation to their insertion on

thalamus?

Answer. Based on the position of the calyx, corolla, and androecium (with respect to
the ovary on the thalamus), the flowers are described as hypognous, perigynous,
and epigynous.
In hypogynous flowers, the ovary occupies the highest position on the thalamus
while other floral parts are situated below it. In such flowers, the ovary is superior
e.g., China rose, mustard etc.
In perigynous flowers, the ovary is situated at the centre and other floral parts are
arranged on the rim of the thalamus. The ovary here is said to be half inferior e.g.,
plum, rose, peach
In epigynous flowers, the thalamus grows around the ovary fusing with its wall. The
other floral parts are present above the ovary. Hence, the ovary is said to be inferior
e.g., flowers of guava and cucumber.