Bal Bharati Public School, Navi Mumbai
Subject: Science
Class: X
Topic: How do organisms reproduce? (Part-3)
Subtopics
1. Structure of a flower
2. Pollination
3. Fertilization
4. Structure of a Seed
Flower
• Flower is the reproductive
organ of a plant
• It forms seeds that give
rise to new plants in
Angiosperms.
• A complete flower has
the following four parts:
i. Sepals
ii. Petals
iii. Stamen
iv. Pistil/Carpel
Non-essential parts of Flower
i. Sepals: 5 or more
green leafy like
structures which
protect the flower bud
ii. Petals: 5 or more
brightly coloured
structures which
attract insects, birds or
mammals for
pollination of flowers
Essential parts of Flower
1. Stamen- It is the male
reproductive part of a
flower.
2. Pistil- it is the female
reproductive part of a
flower. Pistil is present
in the centre of a flower.
Parts of Stamen
i. Anther- a small sac-like
apical head at the top
ii. Filament- a stalk that
attaches anther to the
flower
iii. Pollen grains- hundreds of very small structures, are
yellowish in colour, formed inside the anther. The male
gamete/sex cells are produce in the pollen grain.
Parts of Pistil
i. Stigma- the terminal
part which may be
sticky
ii. Style-middle elongated
tubular part
iii. Ovary- The swollen bottom part which contains
ovules. The female gamete or egg is formed in the ovule.
Unisexual flower
• The flower is unisexual when it
contains either stamens or pistil
• For example: papaya, watermelon
Female Papaya Flower
Male Papaya Flower
Watermelon
Bisexual Flower
• The flower is bisexual when it contains both stamens
and pistil.
• For Example: Hibiscus, mustard
Pollination
• The transfer of pollen grains from the anthers to the
stigma of pistil is known as pollination
• Pollination is of two types:
i. Self pollination takes place within the same flower
or between two flowers on the same plant
ii. Cross pollination occurs between two flowers of
two different plants of same species.
• This transfer of pollen from one flower to another is
achieved by agents like wind, water or animals.
Self Pollination
Cross-Pollination
Cross-pollination
Pollination
by
Wind
In
Maize
Pollination
by
Water
In
Vallisneria
Pollination by Bird
Pollination by Bird
Fertilization
• After the pollen lands on a suitable
stigma, it has to reach the female germ-
cells which are in the ovary.
• For this, a tube grows out of the pollen
grain and travels through the style to
reach the ovary.
• The tip of the pollen tube dissolves to
release the male gamete which fuses
with the egg cell in the ovule to form a
Zygote.
• The fusion of male gamete and egg cell is
called Fertilization.
Seed and Fruit Formation
• After fertilisation, the zygote divides several times to
form an embryo within the ovule.
• The ovule develops a tough coat and is gradually
converted into a seed.
• The ovary grows rapidly and ripens to form a fruit.
• Meanwhile, the petals, sepals, stamens, style and
stigma may shrivel and fall off.
Structure of Seed
• A seed has an outer seed coat.
• The seed consists of cotyledons
which store food and a short curved
structure called embryo.
• The embryo has two parts:
i. Radicle- root forming part
ii. Plumule- shoot forming part
The embryo develops into a seedling under appropriate conditions.
This process is known as germination.
Let us Recapitulate....
• A complete flower has four parts: Sepals, Petals, Stamen and Pistil.
• Stamen consists of anthers with a stalk called Filament.
• Carpel consists of stigma, style and ovary
• The transfer of pollen grains from the anthers to the stigma of pistil is
known as pollination
• Fertilization occurs after pollination when male gamete in the pollen grain
fuse with the egg cell in the ovule. .
• Ovule develop into seed and ovary develop into fruit.
• Every seed consists of a seed coat and an embryo.
• An embryo has one or two cotyledons, a radicle and a plumule.
• On germination, the plumule develops into shoot system and the radicle
into the root system.
Assignment-3
1. What is the importance of flower for a plant?
2. Distinguish between unisexual flower and bisexual flower
giving two examples of each.
3. Define Pollination. What is the difference between self-
pollination and cross-pollination?
4. Explain the process of fertilization in angiosperms with the
help of a diagram
5. Describe the structure of a dicot seed and illustrate the
answer with a diagram.
Links
• Structure of a flower
• https://www.youtube.com/watch?v=jJ5K78_TIEY
• Parts of flower and Pollination
• https://www.youtube.com/watch?v=SiFaN2xQg5g
• Fertilization in Plants
• https://www.youtube.com/watch?v=3cmB7bnymnk
• Sexual Reproduction in Flowering Plants
• https://www.youtube.com/watch?v=2ycl2E9r-_o
• Structure of a Dicot Seed
• https://www.youtube.com/watch?v=SANJW_ZIYrc
