NAME – PALAK SINGH

CLASS – 8 B
TOPIC – REPRODUCTION IN
PLANTS
SUBJECT – BIOLOGY
 VEGETATIVE PROPAGATION:
In some flowering plants, a new plant can arise from a vegetative part such as root, stem or
leave without the help of any reproductive organ. This is called vegetative propagation . It
takes place in plants which do not produce seeds or whose seeds cannot germinate . It is a
type of asexual reproduction as there is no fusion gametes and no seed is formed . Vegetative
propagation can occur by natural as well as artificial methods.

• By aerial stem
• By underground stem
Vegetative propagation by natural methods :

Vegetative propagation by artificial methods :

• Layering
• Cutting
• Grafting
• Tissue culture
 VEGETATIVE PROPAGATION BY NATURAL METHODS
:
BY UNDERGROUND STEM – The underground stems of some plants have
buds that serve as means of vegetative propagation .
• TUBER : This is a swollen
• RHIZOME : This is a short,
fleshy underground stem . branched , underground stem. It
Potato tuber has many small has distinct nodes and internodes
buds called eyes , each of bearing buds , which can grow
which can grow into new into new plants. Ginger , banana
plant. and canna grow from rhizomes.

• CORM : It is a thickened round

, underground stem that • BULB : It is an underground
consist of a swollen base stem with a bud and
surrounded by scale leaves . membranous leaves called
It has one or more buds that scales . Garlic , tulips ,onions
grow into new plants . For grow from bulbs .
example, Gladiolus.
•
•
BY AERIAL STEM – In some plants such as strawberry, a slender branch arising from the base of
the stem grows and bends to touch the soil . It develops roots and buds at the point of contact with soil and
develops into a new plant.
In some grasses and mint , the stem gross along the soil forming
roots at intervals and giving rise to new plants. When the new plant is mature enough, the part of the stem joining
the new plant withers away and the plant grows on its own.

BY ROOT : plant such as sweet potato and dahlia have BY LEAVES : Some plants such as Bryophyllum and
fleshy tuberous roots with adventitious buds . These Kalanchoe produce adventitious buds at the margin of their
buds when detached and planted in soil, can give rise to leaves. When the leaf falls on moist soil, the buds develop
new plants. into small plantlets as they grow. The plantlets grow into
independence plants on separation from the leaf.
VEGETATIVE PROPAGATION BY ARTIFICIAL
METHODS:
Vegetative propagation is a faster method of reproduction, hence it is used in gardens and
nurseries. The methods that have been adopted by human beings for vegetative propagation
are called artificial propagation.
Some of these methods are cutting , grafting , layering and tissue culture.

CUTTING – In this method, a part of the stem with an

axillary bud is cut from a healthy plant and planted in moist
soil. Over a period of time , roots develop at the lower end of
the cutting. Also new leaves developed from The buds at its
upper and to form a new plant. Cutting is extensively used by
gardeners for growing rose , Bougainville and cacti plants .
Sugarcane and pineapple plants are also grown from stem
cuttings.
LAYERING – In this method , a branch of the plant is bent and a part of it is covered
with soil. After a few days , roots develop from the part under the soil. The branch is then
cut off from the main plant and planted in the soil. It grows as a new plant. Lemon , rose
and jasmine plants are grown in this manner.

GRAFTING – It is a method in which two different plants a combined to

obtain a plant with superior qualities . A stem cutting called scion from one plant is
attached and tied to the rooted stem called stock of another plant. After few days,
the stock and the scion merge together due to rapid division of cells and the bulbs
develops. The stock supplies essential nutrients to the scion . Grafting helps in
developing new varieties by combining the features of two plants. It is usually done
in plants such as mango and rose. In rose , it is done to get flowers of different
colours on one plant.
TISSUE CULTURE – In this method, plants are
grown artificially in a test tube under laboratory conditions.
This technique is also called micropropagation . A small
piece is cut off from the growing tip of a plant. This tissue is
grown in a suitable nutrient medium. It grows into an
unorganized mass of cells called callus . Small parts of this Callus
callus are put in another medium containing hormones to
induce cell differentiation and formation of plantlets. The
plantlets are then transplanted into the soil or pots to grow
into mature plants.
Since an unlimited number of plants can be
produced, this technique is used for the propagation of
ornamental plants such as Chrysanthemum , Asparagus and
orchids .
PLANTLET STAGE
ADVANTAGES OF VEGETATIVE
PROPAGATION:
• Vegetative propagation is a faster method of growing plants
than growing them from seeds.
• Plants produced by vegetative propagation bear flowers earlier
than those produced from seeds .
• Vegetative propagation is extremely useful for production of
seedless plants such as banana, grapes and sugarcane.
• New plants produced via vegetative propagation are exactly
the same as the parent plant and can survive even in
unfavourable conditions.
DISADVANTAGES OF
VEGETATIVE PROPAGATION :

• All offsprings from the same parent have the same features. So ,
they are all prone to the same infections , which can result in the
destruction of an entire crop.
• Over a period of time , newer generations of plants produced via
vegetative propagation lose their vigour.
• There are chances of overcrowding as there is no dispersal.
Sexual reproduction in plants :
Sexual reproduction is a common method of reproduction in flowering plants. Seeds are produced as a result of sexual
reproduction , which germinate and grow into new plants.

STRUCTURE OF A FLOWER -
Flowers are the organs of reproduction in seed- bearing plants called
angiosperms. A flower contains male and female gametes. The function of
flowers is to form seeds. Seeds can germinate and developed into new plants.
Flowers differ in their size , shape and colour, yet most of them have a
common structure. Most flowers have four whorls or layers arranged in a
definite order on a fleshy base called thalamus or receptacle. The four whorls
are the calyx , corolla , androecium and gynoecium (or pistil) . The outer two
whorls comprise the calyx (sepals) and corolla (petals). They do not take part
in reproduction. The inner two whorls comprise the androecium (stamens) and
gynoecium (carpels). Androecium is the male part of the flower , while
gynoecium is the female part of the flower. They take part in reproduction. The
structure of a typical flower is described below.
TYPES OF FLOWERS:

Most flowers have all the four whorls , that is , sepals , petals
androecium and gynoecium. They are called complete flowers.
Since both androecium and gynoecium are present in these
flowers , they are also called bisexual or hermaphrodite PISTILLATE FLOWER
flowers. For example, hibiscus , rose , petunia and so on.
Some flowers lack either a male whorl or a female
whorl. They are called incomplete flowers. Such flowers are
unisexual and will be either male , that is staminate flowers , or
female, that is pistillate flowers. For example, papaya and maize.
There are some flowers that have neither androecium not
gynoecium. Such flowers are called neutral flowers. For
example , ray florets of sunflower .

STAMINATE FLOWER
 POLLINATION
For fusion of gametes to occur and seeds to be formed , pollen grains produced in the anther must be transferred to the
stigma of the pistil. The process by which the pollen grains from the anther of a flower are transferred to the stigma of the
same or another flower is called pollination. Pollination occurs naturally as well as artificially. Natural pollination is of two
types .

Self pollination – The process of transfer Cross pollination – The process of

of pollen grains from the anthers to the stigma of transfer of pollen grains from the anthers of a
the same flower, or another flower of the same plant flower to the stigma of a flower of another plant of
is called self pollination. the same species is called cross pollination.
 AGENTS OF
POLLINATION
Wind , water , insects , bird and other animals help in the transfer of pollen grains from the anther of one flower to the stigma
of another flower. They are , therefore, called agents of pollination. Depending on the external agents involved , Cross
pollination is classified as -

• POLLINATION BY INSECTS : Pollination by insects is called entomophily. It is the

most common method of natural pollination . Insects such as bees and butterflies visit
flowers to collect nectar. In the process, pollen grains get stuck to their body . When
these insects visit another flower , pollen grains get transferred to the stigma of that
flower. Flowers pollinated by insects are large , brightly coloured and often scented;
for example, Salvia, rose and marigold. Most flowers also produce nectar and are
sweet smelling; for example , night jasmine . Pollen grains and the stigma of most of
these flowers are sticky.

• POLLINATION BY WIND : Pollination by wind is called anemophily. Flowers of

plants such as rice , maize and grasses are pollinated by wind. Most wind pollinated
flowers are small, and have dry and light pollen grains which can be easily carried by
wind. Pollen grains are produced in very large quantities so that at least some have a
chance to reach the stigma. The style projects out and has a large, feathery stigma so
that the pollen flying in the wind can be easily received.
•
•
• POLLINATION BY WATER : Pollination by water is called hydrophily. It occurs
in aquatic plants such as Hydrilla and Vallisneria . Flowers pollinated by water are
very light so that they can easily float on the surface . They do not produce nectar.
Pollen grains are produced in large quantities. Male and female flowers are
usually produced on separate plants . In Vallisneria , the male flower is submerged
in water. On maturity , it gets detached and floats on water. The female flower has
a long stalk that too floats on the surface of water . When the male flower comes
in contact with the female flower, the pollen grains get deposited on the stigma
and pollination occurs.
•
•
• POLLINATION BY ANIMALS : Birds , squirrels and bats also act as agents of
pollination when they suck nectar from flowers. In such cases, flowers are usually
large and bright coloured , growing on tall trees. For example, silk cotton tree.
 ARTIFICIAL
POLLINATION
Artificial pollination is performed to produce a new variety of plant with
certain required characteristics. In this process two different varieties of a
crop plant with the desired characteristics are selected. For example, one
variety may be high – yielding ( higher-grain producing) and the other
variety may be disease-resistant. After selection of these varieties, cross –
breeding is done by artificial pollination to get a variety of plant which has
both the desired characteristics from the parent varieties. This is called
hybridization. The new variety formed is called a hybrid.
Many hybrid high – yielding varieties of wheat , rice and maize
have been produced by the process of hybridization. The steps in the
process are explained in the picture.

THE PROCESS OF
HYBRIDIZATION
 FERTILIZATI PROCESS OF FERTILIZATION

ON
When a pollen grain reaches the stigma , it
begins to grow a pollen tube that travels
down through the style to reach the ovules
inside the ovary. The nucleus of pollen tube
divides to form two male gametes. A male
gamete or male sex cell travels down each
pollen tube and fuses with the egg cell (or a
female gamete) inside an ovule. The process
of fusion of the male gamete with the female
gamete is called fertilization. The single cell GERMINATING POLLEN GRAINS
produced as a result of fertilization is called
zygote . The steps of the process of
fertilization are given in the picture on the
left side.
 SEED FORMATION
After fertilization, the sepals , petals and stamens fall off. The stigma and style also
wither away. The ovary containing ovules , each with a fertilized egg ( zygote ) ,
continues to grow. The zygote divides and grows into an embryo which has two
cotyledons and an embryonic axis. The fertilized and developed ovules changes into a
seed. A sees is a fertilized and mature ovule which can grow into a new plant under
favourable conditions.

FRUIT
FORMATION
A fruit is a ripened ovary that contains one or more seeds. A fruit
can be fleshy or dry depending on the wall of the ovary. The wall of
the ovary can be fleshy as in the papaya , tomato and cucumber, or
is dry as in pea.
The fruit protects the seeds from insects , diseases and extreme
climatic conditions. TOMATO
 GERMINATION OF
SEEDS
A typical seed of gram and bean consists of a seed coat and embryo or baby plant . On removing the seed coat , the
embryo is seen. It consists of two fleshy cotyledons and a short curved structure called embryonal axis. The
cotyledons are attached to the embryonal axis. The axis consists of two parts . The lower part is called the radicle ,
which forms the root system. The upper part consist of a small leaf is structure , the plumule. It grows into the shoot
system.
The process by which a sleeping or dormant embryo becomes active and grows into a new plant is known
as germination. Water , a suitable temperature and oxygen are required for seeds to germinate.