Notes L-11
Reproduction in Plants
Points to ponder:
1) The process of producing young ones from their parents is known as
reproduction.
2) The formation of new plants from the cells of a single parent is called
asexual reproduction.
3) Vegetative reproduction is also a type of asexual reproduction in
which a cell, tissue, or part of an organ of a plant develops into a new
organism.
4) The formation of new plants through the fusion of male and female
gametes is called sexual reproduction.
5) Types of asexual reproduction:
(a) Budding
(b) Fragmentation
(c) Spore Formation
6) Types of Vegetative reproduction:
(a) Natural Methods
(i) Roots eg Dahlia, sweet potato and Asparagus
(ii) Stems eg Oxalis, grass, Chrysanthemum, vallisneria and wild
strawberry.
(iii) Leaves eg Bryophyllum develop small buds, called adventitious
buds.
(b) Artificial Methods
(i) Cutting
(ii) Grafting
(iii) Layering
7) Sexual reproduction is carried out only in flowering plants.
8) Flowers are the reproductive organs of a plant.
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9) Complete or bisexual flowers are those flowers that contain both male
and female reproductive cells called gametes.
10) Incomplete or unisexual flowers are those flowers which have either
male or female gametes.
11) Parts of a flower are: Sepals, Petals, Stamens (male organ) and Pistils
(female organ).
12) The transfer of pollen grains from the anther to the stigma is known
as pollination.
13) Self pollination- pollen grains are transferred from the anther to the
stigma of the same flower.
14) Cross pollination- the pollen grains are transferred from the anther
of one flower to the stigma of another flower of the same kind.
15) Agents of pollination are wind, water and insects.
16) The process of fusion of male and female gametes is called
fertilization.
17) The fruit is the seed-bearing part or the ripened ovary of the
flowering plant.
18) The seed is the ripened ovule which contains an embryo and is
covered by a protective coat.
19) The process by which the embryo in the seed becomes active and
begins to grow into a new plant is called germination.
Short answer questions:
1) Reproduction means producing young ones from their parents. Plants
reproduce by sexual, vegetative and asexual means.
Sexual reproduction- involves two parents and the fusion of male and
female reproductive cells.
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Vegetative reproduction- involves a cell, tissue or part of an organ of a
plant develops into a new organism.
Asexual reproduction- under favorable conditions a new plant body is
formed from a single parent.
2)
Sexual Reproduction
Asexual Reproduction
i) Sexual reproduction takes place i)Asexual reproduction takes
by the formation of seeds.
place either by the simple
division of the plant body into
two or more parts or by the
formation of spores.
ii) It involves two parents.
ii) it involves single parent.
3) Fragmentation is a very common form of asexual reproduction found
in Algae. In this process, the adult organism just breaks up into two or
more pieces called fragments. Each of these fragments grows up to
become a new plant.
4) Natural vegetative reproduction means plants reproduce from the
vegetative parts naturally without the involvement of humans. They do
so with the help of stems, roots and leaves.
5) There are three common agents of pollination: Wind, Water and
Insects.
6) The process by which the embryo in the seed becomes active and
begins to grow into a new plant is called germination. Germination takes
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place when the seed has matured and suitable conditions of air, water,
and temperature are available.
Long Answer Questions:
1) The advantages of vegetative reproduction are listed below:
i) It is faster and more certain method of reproduction. Sometimes the
seed may not germinate due to unfavourable conditions. But in this case,
a new plant directly grows from a part of the parent plant.
ii) New plant resembles the parent plant exactly. Thus, it helps in
conserving characteristic features of the parent plant.
iii) Plants that do not flower or have seeds can reproduce by this
method.
2) The formation of new plants from the cells of a single parent is called
asexual reproduction. Asexual reproduction is of the following types:
i) Budding: In this process, a small bulb-like cellular outgrowth, called
bud, is formed from the cell. This bud keeps on increasing in size and
forms an independent organism which separates from the parent, e.g.
Yeast.
ii) Fragmentation: In this process, the adult organism just breaks up into
two or more pieces called fragments. Each of these fragments grows up
to become a new plant, e.g. Algae, such as Spirogyra and Fucus.
iii) Spore Formation: Spores are microscopic single-celled or severalcelled reproductive bodies that are mostly spherical in shape. They are
protected by a thick wall when conditions (such as humidity and
temperature) are unfavorable. Once the conditions for germination are
favourable, these spore burst out of the thick wall, start multiplying, and
grow into new plants, e.g. Ferns and mosses.
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3) Some of the artificial methods in vegetative propagation are as
follows:
i) Cutting- some plants can be propagated through cuttings from their
stem. When one end of a cutting of these plants is buried in soil. It
develops shoots and roots and grows into a new plant e.g. rose, cactus
and bougainvillea.
ii) Grafting- it involves the following steps:
(a) A bud, or a cutting that has several buds called the scion, of one
plant is placed over the cut stem with roots of another plant called the
stock.
(b) The scion and the stock are then firmly tied together.
(c) The stock supplies water and minerals to the scion. In due course,
new cells develop in the area where they are joined and a new variety of
plant develops, e.g. rose, mango and guava.
(iii) Layering- in this process, a young branch is lowered down and bent
towards the ground and covered by moist soil layer. After sometime,
roots arise from the branch and grow downwards. The branch can then
be cut off from the parent plant and allowed to grow into a new plant.
4) The transfer of pollen grains from the anther to the stigma is known as
pollination. There are two types of pollination: self-pollination and crosspollination.
Agents of Pollination:
i) Wind- Wind blows away pollen grains from the anthers of one flower
to the stigma of another flower. Such flowers are small, not brightly
coloured, and do not produce nectar e.g. wheat, rice, and maize.
ii) Water- Water pollinated flowers release their pollen grains into the
water, and are slowly carried to other flowers by water currents e.g. sea
grass, and Vallesneria.
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iii) Insects- Many insects visit flowers for nectar. During the process,
some pollen stick to the body parts of these insects. When these insects
visit another flower, the pollen grains fall on the stigma. Insect-pollinated
flowers usually have a sweet smell, brightly coloured petals, and are rich
in nectar e.g. sweet pea, orchids, and jasmine.
5) After the successful pollination, the stigma secretes nutrients. The
pollen grains absorb these nutrients and the pollen tube with the male
gametes, starts growing till it reaches ovary. Once the pollen tube
reaches the ovule, the male gamete is released and fused with the
female gamete. The cell which results after fusion of the gametes is
called a zygote. The process of fusion of male and female gametes is
called fertilization.
6) After fertilization, the ovary enlarges to form the fruit:
a) The wall of the ovary becomes the fruit wall.
b) The ovules become the seeds.
c) A fruit may have one or more seeds.
d) Petals, sepals and other parts of the flower dry up and fall off.
The fruit is the seed-bearing part or the ripened ovary of the flowering
plant.
The seed is the ripened ovule which contains an embryo and is covered
by a protective coat.
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