NCERT Solutions for Class 11 Biology Chapter 5 Morphology of Flowering Plants

NCERT
SOLUTIONS
CLASS - 11th

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Class : 11th
Subject : Biology
Chapter : 5
Chapter Name : Morphology Of Flowering

Q1 What is meant by modi cation of root? What type of modi cation of root is found in the
(a) Banyan tree
(b) Turnip
(c) Mangrove trees

Answer. Primarily, there are two types of root systems found in plants, namely the tap root system and
brous root system. e main function of the roots is to absorb water and minerals from the soil. However,
roots are also modi ed to perform various other functions. The roots of some plants act as storage sites
for food, some provide support to massive plant structures, while others absorb oxygen from the
atmosphere.
Roots and its modi cations in various plants:
(a) 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) Turnip : The roots of turnip (Brassica rape) help in the storage of food. Similar food-storing roots are
found in radishes, carrots, and sweet potatoes.
(c) Mangrove tree : 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.

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Q2 Justify the following statements on the basis of external features
(i) Underground parts of a plant are not always roots
(ii) Flower is a modi ed shoot

Answer. (i) Various parts of plants are modi ed into underground structures to perform various
functions such as stems, leaves, and even fruits. The stems in ginger and banana are underground and
swollen due to storage of food. They are called rhizomes. Similarly, corm is an underground stem in
Colocasia and Zamin-khand. The tips of the underground stem in potato become swollen due to the
accumulation of food and forms tuber. Tubers bear eyes, which are subtended by a leaf scar. Basal leaves
in onions become eshy because of the accumulation of food. In peanuts, the ower after fertilization
gets pushed inside the soil by growing a ower stalk. The formation of fruits and seeds takes place inside
the soil.

(ii) During the owering season, the apical meristem gives rise to the oral meristem. The axis of the
stem gets condensed, while the internodes lie near each other. Instead of leaves, various oral
appendages arise from the node. Therefore, it can be said that the ower is a modi ed shoot.

Page : 82 , Block Name : Exercise

Q3 How is pinnately compound leaf different from palmately compound leaf?

Answer.

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Q4 Explain with suitable examples the different types of phyllotaxy?

Answer. Phyllotaxy refers to the pattern or arrangement of leaves on the stem or branch of a plant. It is
of three types, alternate, opposite, and whorled phyllotaxy. In alternate phyllotaxy, a single leaf arises
from the node of a branch. This type of phyllotaxy is observed in the sun ower, mustard, and peepal.
Plants with opposite phyllotaxy have two leaves arising from the node in opposite directions. It is found
in guava and jamun plants. Plants with whorled phyllotaxy have three or more leaves arising from the
node. It is found in Alstonia.

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Q5 De ne the following terms:
(a) Aestivation
(b) Placentation
(c) Actinomorphic
(d) Zygomorphic
(e) Superior ovary
(f) Perigynous ower
(g) Epipetalous Stamen

Answer. (a) Aestivation : The term 'aestivation' refers to the mode in which sepals or petals are arranged
in a oral bud with respect to other oral members. There are four types of aestivation in plants i.e.,
valvate, Wisted, imbricate, and vexillary.
(b) Placentation : The term 'placentation' refers to the arrangement of ovules within the ovary of a
ower. It is primarily of ve types, namely marginal, basal, parietal, axile, and free central.
(c) Actinomorphic : Actinomorphic owers can be divided into two radial halves by any radial plane
passing through its centre. Examples of these owers include chilly and mustard.
(d)Zygomorphic : Zygomorphic owers are those owers which can be divided into two similar halves by

a single vertical plane. Examples of these owers include pea and beans.
(e) Superior ovary : Superior ovary owers are those owers in which the gynoecium is present at the
highest position, while other oral parts are arranged below it. A ower with this arrangement is
described as hypogynous. Examples include brinjal and mustard.
(f) Perigynous ower : In perigynous owers, the gynoecium is present in the centre and the rest of the
oral parts are arranged at the rim of the thalamus at the same level. Examples include plum and rose.
(g) Epipetalous Stamen : Epipetalous stamens are stamens attached to the petals. They are found in
brinjal.

Q6 Differentiate between
(a) Racemose and cymose in orescence
(b) Fibrous roots and adventitious roots
(c) Apocarpous and syncarpous ovary

Answer.
(a) Racemose and cymose in orescence

(b) Fibrous roots and adventitious roots

(c) Apocarpous and syncarpous ovary

Q7 Draw the labelled diagram of the following:
(i) Gram seed
(ii) V.S. of maize seed

Answer.

Q8 Describe modi cations of stem with suitable examples.

Answer. Stems of various plants have undergone modi cations to perform different functions.
Underground stems or storage stems: Examples: Rhizomes, Corms, tubers.
In ginger and banana, the underground stem is called a rhizome. The underground stem in Colocasia
(arvi) is known as corm. Rhizomes and corms are underground stems, modi ed for the storage of food.
Also, these stems help in vegetative reproduction of these plants. The tips of the underground stem in
potato plants become swollen due to the accumulation of food. The potato is a tuber that helps in the
storage of food and bears eyes on it. Subtended by a leaf scar, these eyes bear buds that give rise to new
plants.
Supportive stems:
Example: tendril
The stem in some weak plants bear thin, slender, and spirally-coiled structures called tendrils that help
the plant get attached to nearby structures for support. Tendrils are found in cucumbers, melons, and
other members of the family Cucurbitaceae.
Protective stems:
Example: Thorns
The stem in bougainvillea and citrus plants (like lemon and orange) bear sharp, pointed structures
called thorns, which provide protection to the plant from herbivores.
Photosynthetic stems:
Example: Opuntia
The stem in the Opuntia is green. It carries out the process of photosynthesis in the absence of leaves.
Others stem modi cations.
In some plants, underground stems such as grasses spread in the soil and help in perenation. These
stems are called runners.
The short lateral stem called the offset in some aquatic plants (such as Eichhornia) bears leaves and
tufts of roots at the node and gives rise to new plants.

Q9 Take one ower each of families Fabaceae and Solanaceae and write its semi- technical description.

Also draw their oral diagrams after studying them.

Answer. Family Fabaceae/Papilionaceae (pea plant)
Fabaceae/Papilionaceae is a sub-family of the Leguminosae family.
Vegetative features:
Habit: Pinnately compound, alternately arranged with leaf tendrils with the pulvinus present at the leaf
base along foliaceous stipules.
Root: Tap root system with root nodules.
Floral features: In orescence: Racemose, generally axial than terminal Flower: Zygomorphic and
bisexual owers are found.
Calyx: It contains ve sepals which are gamosepalous while aestivation is imbricate.
Corolla: It contains ve 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.

(2) 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: In orescence: Solitary and axillary Flowers: Actinomorphic, bisexual owers.
Calyx: Calyx is composed of ve sepals that are united and persistent. Aestivation is valvate.
Corolla: Corolla consists of ve united petals with valvate aestivation.
Androecium: It consists of ve epipetalous stamens.
Gynoecium: It consists of bicarpellary syncarpous superior ovary with axile placentation.
Fruits: Berry
Seeds: Numerous, endospermous
Floral formula:

Economic importance: Peas are used as vegetables for making various culinary preparations.

Q10 Describe the various types of placentations found in owering plants.

Answer. Placentation refers to the arrangement of ovules inside the ovary. It is of ve basic types.
(A) 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.

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

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

(D) 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 sun ower.

(E) 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.

Q11 What is a ower? Describe the parts of a typical angiosperm ower?

Answer. A ower can be de ned as the reproductive unit of any owering plant (angiosperms). Flowers
carry out sexual reproduction in angiosperms. A typical ower is a modi ed stem with a condensed axis.
A ower has four different parts i.e., the calyx, corolla, androecium, and gynoecium. Androecium and
gynoecium represent the male and female reproductive organs of a ower (respectively). Bisexual
owers are those which contain both androecium and gynoecium, while unisexual owers contain either
gynoecium or androecium. The corolla and the calyx are generally distinct, but may sometimes be fused
(called perianth). A ower that contains all four oral parts is called a complete ower.
Parts of owers
(A) The calyx forms the outermost whorl of a ower, which contains sepals. They are green, leaf— like
structures that cover and protect the owers during the bud stage. When the sepals of a ower are free,

they are called polysepalous, while fused sepals of a ower are called gamosepalous.
(B) The corolla of a ower is a layer that lies inside the calyx. It contains beautifully coloured petals,
which help in attracting insects for pollination. When the petals are free, they are called polypetalous,
while fused petals are called gamopetalous.
(C) The androecium or the stamen is the male reproductive part of a ower. It consists of two parts, the
lament and the bilobed anther. The bilobed anther is the site for meiosis and the generation of pollen
grains.
(D) Gynoecium represents the female reproductive part of a ower. 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.

Q12 How do the various leaf modi cations help plants?

Answer. The main function of the leaves is to carry out the process of photosynthesis. However, in a few
plants, leaves are modi ed to perform different functions.
(a) Tendrils: The leaves of a pea plant are modi ed into tendrils that help the plant in climbing.
(b) Spines: The leaves in cactus are modi ed into sharp spines that act as an organ of defense.
(c) Phyllode: The leaves of some Australian acacia are short-lived and soon replaced by attened, green
structures called phyllodes that arise from the petiole of the leaves. The petioles in these plants
synthesize food.
(d) Pitcher: The leaves of the pitcher plant are modi ed into pitcher-like structures, which contain
digestive juices and help in trapping and digesting insects.

Q13 De ne the term in orescence. Explain the basis for the different types of in orescence in owering
plants.

Answer. In orescence is the manner in which the owers are arranged on the owering axis. During the
owering season, the vegetative apex of the stem gets converted into a oral meristem. Based on
whether the oral axis continues to grow or end in a ower, in orescence is classi ed into racemose and
cymose. In racemose in orescence, the oral axis continues to grow and produces owers laterally. On
the other hand, in cymose in orescence, the main axis terminates into a ower. Hence, it is limited in
growth.

Q14 Write the oral formula of an actinomorphic bisexual, hypogynous ower with ve united sepals,
ve free petals. Five free stamens and two united carpals with superior ovary and axile placentation.

Answer. The oral formula of the described ower is represented as:

Actinomorphic owers are represented by the symbol ⊕

A bisexual ower is indicated by
The calyx contains ve united sepals which can be represented as K (5)

The corolla consists of ve free petals and it represented as C5

The androecium consists of ve free stamens and is represented by A 5

The gynoecium consists of a superior ovary with two united carpels and axle
placentations, which can be represented as G
–– (2)

The calyx contains ve united sepals which can be represented as K (5)
. The corolla consists of ve free
petals and it represented as C .
5

The androecium consists of ve free stamens and is represented by A . 5

The gynoecium consists of a superior ovary with two united carpels and axile placentation.

Q15 Describe the arrangement of oral 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 owers are described as epigynous, perigynous, and epigynous. In hypogynous owers,
the ovary occupies the highest position on the thalamus while other oral parts are situated below it. In
such owers, the ovary is superior e.g., China rose, mustard etc. In perigynous owers, the ovary is
situated at the centre and other oral 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 owers, the thalamus grows around the
ovary fusing with its wall. The other oral parts are present above the ovary. Hence, the ovary is said to
be inferior e.g., owers of guava and cucumber.