Reproduction is one of the most fundamental processes carried out by living organisms.

However,
there are differences in the way living organisms exhibit the process.

Modes Of Reproduction In Plants

In plants, reproduction is carried out via two modes:

• Asexual Mode – New plants are obtained without producing seeds

• Sexual Mode – New plants are obtained from seeds.

Asexual Reproduction In Plants

In asexual reproduction in plants, plants are reproduced without the formation of seeds. Following
are a few ways in which plants reproduce asexually.

Vegetative Propagation
As the name suggests, reproduction occurs through the vegetative parts of a plant such as stems,
leaves, buds, and roots. These plants take less time to grow and are exact replicas of their parents
as they are reproduced from a single parent.

Budding
Small bulb-like projections arise from yeast cells, eventually detaching itself from the parent cell.
This then matures to grow into a new yeast cell. These, in turn, produce more buds and the chain
continues forming a number of new yeast cells within a short period of time.

Fragmentation
Some organisms have the ability to break into two or more fragments, with the new fragment
becoming a new, independent individual. They multiply rapidly in a short period of time.

Spore Formation
Spores are present in the air and are covered by a hard protective coat to bear low humidity and
high-temperature conditions. Spores germinate and develop into new organisms under favourable
conditions.
Micropropagation
An explant is taken from a plant and allowed to grow in a nutrient medium under controlled
conditions in the laboratory. The cells divided rapidly and form an unorganised mass of cells. This
unorganised mass of cells is known as a callus. The callus is transferred to another nutrient medium
to facilitate the differentiation of different parts of the plant. The plantlets are then transferred to
the fields.

Advantages of Asexual Reproduction in Plants

• A large number of plants can be produced within a short period.
• The exact copies of the parent plant are produced.
• Many seedless varieties are obtained through the vegetative method.
• Less attention is required by the plants grown through asexual means than through seeds.

Sexual Reproduction In Plants

The reproductive parts of plants are flowers, Stamen being male reproductive part and pistil being
the female reproductive part. If one of these reproductive parts are present in a flower, it is said to
be a unisexual flower. Example: papaya. If both Stamen and Pistil are present in flowers they are
called bisexual flowers. Example: rose.

Pollen grains form the male gametes. The pistil consists of style, stigma, and the Ovary. The ovary
consists of one or more ovules. Ovules are where female gametes or the egg is formed. Female
and male gametes fuse to form a zygote.

Pollination
When pollen is transferred from the anther to the stigma of a flower through carriers such as insects
it is called pollination. It can be a case of self-pollination if pollen lands on the stigma of the same
flower or another flower of the same plant. If pollen grains land on the stigma of a flower of a
different plant, but of the same kind, it is called cross-pollination.

Fertilization
A zygote is formed as a result of the fusion of gametes which later develops into the embryo. Fruits
and seeds are formed post-fertilization. Ripened ovary goes on to become a fruit. Ovules give rise
to seeds which contain the embryo in a protective covering.
Asexual Reproduction In Plants
“Asexual reproduction is the mode of reproduction that does not involve the fusion of male and
female gametes and produces individuals that are genetically identical to the parent.”

Asexual Reproduction In Plants

Asexual reproduction in plants occurs through budding, fragmentation, vegetative propagation,
and spore formation. No flowers are required for this method. The plants produced by asexual
reproduction thrive well in stable environments.

Types Of Asexual Reproduction In Plants

Asexual reproduction in plants takes place in two ways:

• Naturally
• Artificially

Natural Methods
Natural methods of asexual reproduction include self-propagation. The different ways in which a
plant self propagates are mentioned below:

• Plants such as ginger, onion, dahlia, potato, grow from the buds present on the surface of the
stem. A stem tuber has several eyes on the surface. Under favourable conditions, these eyes
sprout producing leafy shoots.
• In sweet potato, new plants can grow from the adventitious buds or stolons.
• In Byophyllum, the small buds o the margin of the leaves gets detached and grows into an
independent plant.

Budding
Budding is the mode of asexual reproduction wherein a new plant is developed from an outgrowth
known as the bud. A bud is generally formed due to cell division at one particular site.

For example, if you keep a potato for a long time, you can notice a number of small outgrowths,
which are commonly referred to as ‘eyes’. Each of them can be planted which will grow up like a
clone of an original potato plant.
Budding

Vegetative Propagation
It is any form of asexual reproduction occurring in plants, in which new plants are produced from
the vegetative parts of the plants, i.e. roots, stems or buds. Vegetative propagation in plants can
occur both by naturally or also can be artificially induced by horticulturists.

The most common techniques of vegetative propagation are:

Stems – Runners are the stems which usually grow in a horizontal form above the ground. They
have the nodes where the buds are formed. These buds usually grow into a new plant.

Roots – A new plant is developed from modified roots called tubers. Example: Sweet Potato

Leaves – In some plants, detached leaves from the parent plant can be used to grow a new plant.
They exhibit growth of small plants, called plantlets, on the edge of their leaves. Example:
Bryophyllum.

Fragmentation
This is a mode of asexual reproduction in which a new plant is produced from a portion of the
parent plant. Each section or a part of the plants develop into a mature, fully grown individual.
Some plants possess specialized structures for reproduction through fragmentation. This type of
reproduction happens naturally where the small part of the plant fall off onto soil and then begin
to grow up into a new plant. This mode is often used by nurseries and greenhouses to produce
plants quickly.

Spore Formation
Many plants and algae form spores in their life cycle. A spore is an asexual reproductive body,
surrounded by a hard protective cover to withstand unfavourable conditions such as high
temperature and low humidity. Under favourable conditions, the spores germinate and grow into
new plants. Plants like moss and ferns use this mode of reproduction.

Artificial Methods
Following are the artificial methods of asexual reproduction in plants:

Cutting
• In this method, a part of a plant is cut along with the node and is buried in the soil.
• The cutting is watered regularly.
• this is the cheapest method of vegetative propagation in plants.

Grafting
• In this method, the parts of two different plants are joined together such that they continue to
grow as a single plant.
• The rooted plant is known as the stock. The other plant is known as the graft.

Layering
It is the method in which a stem attached to a plant is lowered in the ground and covered with soil.
The stem grows roots while attached to the parent plant and then detaches as an independent plant.

Micropropagation
This is the method of producing a large number of plants from an explant under laboratory
conditions within a short time interval. This facilitates the growth of rare and endangered plant
species that are difficult to grow under natural conditions.

Sex

ual Reproduction in Flowering Plants

Flowering plants, also called angiosperms, use a sexual mode of reproduction. Reproduction in
plants, mainly revolves around the flower, which has both the male and the female gametes. All
parts of a flower aid in the process of reproduction, although some of them are sterile. Therefore,
to understand the process of reproduction in flowering plants, we need to look at the different parts
of the flower and their functions.

Explore sexual reproduction in flowering plants notes to learn about the reproductive structure of
the flower and the process of pollination.

Structure of flower

A flower comprises the following parts-

Calyx: It is the outermost whorl of a flower. It comprises units called sepals. In the bud stage,
calyx encloses the rest of the flower. They usually exhibit green colouration, at some other
instances, they may be a colour like petals. This state of Calyx is termed as petaloid. Calyx can
either be prominent or absent.

Corolla: It consists of many numbers of petals and it is the second whorl of the flower. These
petals are sometimes fragrant. They are coloured, thin and soft that would help in the process of
pollination as they would attract animals and insects.

Reproductive Structure of a Flower

Androecium
It is the male reproductive part of a flower, comprising stamens and it is the third whorl. Each
stamen comprises two parts, namely, anther and filament. The tip of the anther is supported by the
filament. Here pollens are produced by meiosis and disappear eventually.

• Anther: This is a four-lobed sac-like structure responsible for pollen formation.

• Filaments: These thread-like structures are attached to the anther, and they keep the anther in
place.

The transverse section of an anther is microsporangia that further forms a pollen sac. The pollen
sac contains pollen grains.

Microsporangia and Microsporogenesis

Microsporogenesis involves the formation of microspores from microspore mother cells by
meiotic division.

The structure of anther: The anther is the breeding part of stamens. Each anther is connected by
two lobes. Each anther lobe comprises two pollen chambers located longitudinally. The
microsporangium is sufficiently supplied with a number of pollen microspores.

Structure of Microsporangia
Microsporangia consist of:

1. Tapetum: The cells are multinucleate and this layer is one of the innermost layers of the wall.
2. Middle layer: It is composed of three to four layers of thin-walled cells. They are located just
beneath the endothelium.
3. Endothecium: This layer is inner to the epidermis. Some cell develops cells of the endothelium.
4. Epidermis: It is a protective outermost single-layer. Cells of the epidermis in Arceuthobium
develop a fibrous thickening and the epidermis is designated as exothecium.

• Formation of Pollen grains: The young anther soon becomes four-lobed as it comprises a
homogenous mass of parenchymatous cells engirdled by the epidermis. Each archesporial initially
present in hypodermal cells divides into the inner primary sporogenous cell and outer primary
parietal cell. Each primary sporogenous cell splits to produce microsporocytes. Each microspore
mother cell meiotically divides to form pollen grains.
• Microgametogenesis (Development of Male Gametophyte): Microspore is partially developed at
this stage and it is the first cell of the male gametophyte. The wall of the pollen grain comprises
exine (outer layer) and inline (inner layer). The outer layer comprises sporopollenin and the inner
layer is made up of pectose and cellulose.
 • Pre-pollination development: The microspores begin to germinate in situ. A smaller generative
cell lies next to the spore wall. A callose layer is placed around the generative cell. Then, the
callose layer dissolves. The anther then sheds the pollen grains. The released pollen grains are
passed to the stigma through pollination. The pollen grain present on the stigma absorbs water
and within some minutes, swells up. The wall of pollen tube secretes hydrolytic enzymes and
exogenous pectinases creating a passage to enter. The generative and vegetative cells are
supplied by the pollen tube. The generative cell splits forming two non-motile male gametes. Tube
nucleus may disintegrate as there is no important function.

Gynoecium
It is the female reproductive organ and the last whorl of the flower. It is composed of pistil and
occupies the central position of the thalamus. The stigma, style, and ovary are the components of
the pistil. The ovary produces ovules internally. Through meiosis, ovules produce megaspores
which in turn develops into female gametophytes. As a result, egg cells are produced.

Gynoecium can be:

Monocarpellary: The gynoecium consists of a single pistil. For eg., peas and beans.

Multicarpellary: Here, gynoecium comprises more than one pistil.

Syncarpous: It is the gynoecium with combined pistil. For eg., Tomato, cucumber.

Apocarpous: It is the gynoecium with free pistil. For eg., Lotus Vinca.

Pistil- Each pistil has three parts:

• Ovary: The ovary is a chamber where ovules (eggs) are stored, waiting for fertilization.
• Stigma: It is attached to the top of the carpel, where the pollen from other flowers lands.
• Style: It is a tubular structure that connects the ovary and the stigma. It is responsible for the
transportation of pollen from the stigma to the ovary and holding the stigma in place.

Megasporangia and Megasporogenesis

The ovule is connected to the placenta with a stalk called funicle. It yields megasporocytes that
form megaspores. Megasporogenesis is the process of arrangement of megaspores of the
megaspore mother cell. The megaspore mother cell divides meiotically. One of the three
megaspores is utilized while the others degenerate. The functional megaspore forms the female
gametophyte.
Pollination

Pollination is an ecological process carried out by all flowering plants. In this process, the matured
pollen grains are transferred from the anther to the stigma for the purpose of sexual
reproduction in flowering plants.

There are two types of pollination:

• Self-Pollination: This process occurs when the pollen grains from the anther is deposited on the
stigma of the same flower, or another flower on the same plant.

• Cross-Pollination: This process occurs when the pollen grains are transferred from the anther of
one flower into the stigma of another flower of different plants of the same species.

Fertilization
After pollination, the pollens are transferred to the ovary through the pollen tube. After reaching
the ovary, one of the male gametes mates with the ovule, or the female gamete (fertilization) and
the other joins with the polar nuclei. The gamete uniting with the eggs results in the production of
a zygote, that gradually develops to be an embryo. The second gamete that unites with the polar
nuclei results in the formation of endosperm nucleus. It supplies nourishment to the embryo. The
fertilization ultimately turns ovules into seeds while the ovary develops into the fruit.

Functions of a Flower
• The main primary function of the flower is the reproduction of the individual and the species.
• They are the modifications of a shoot. Angiosperms of flowers are shaped differently, helping
diverse modes of pollination.
• Flowering plants are heterosporous. They mainly produce two types of spores. Megaspores are
produced inside ovules and Microspores are produced by meiosis inside anthers.
• Flowers provide development of the pollen tube, base germination of pollen, the formation of
gametes and fertilization. The ovarian portion of the carpel is supplied into the fruit. The ovules
are converted into seeds after fertilization. The gametophytes also develop inside the spores in
case of heterosporous plants.
• The flowers that lack one or the other reproductive organ are called unisexual or imperfect. In
ovaries, the different modification helps in the dispersal of seeds and fruits in some floral parts
like a calyx.