Page 121 - Science Class 07

cells causes the flower to be fer lized and an such as wheat, corn, grasses, etc. These flowers
embryo (zygote) to develop. expose pis ls to the wind and carry on the
process of pollina on.
Forma on of Seeds and Fruits
A er the development of the zygote, the flower
slowly withers and only the ovary is le back.
The zygote in each ovule slowly develops into a

seed. But in fruit plants, the ovary changes into a
fruit. It ripens to become sweet juicy and edible.
Pollina ng Agent

The process of pollina on does not occur itself.
It is triggered by insects of wind.
Pollina on by Wind
Let’s see how:
Types of Pollina on
Insects Self-Pollina on : Self-pollina on takes place
Many insects feed on the nectar of flowers. when the pollen of one flower is transfered to
Some other insects a racted by the colour and the s gma of the same flower. Many flowers
odour of the flowers. When they sit on the that are hermaphrodite undergo this kind of
flowers the pollen grain s ck to their body. pollina on. However, there are many
When these insects visit some other flowers advantages and disadvantages of this type of

the pollen grains fall in these flowers which pollina on. Many flowers have various
trigger pollina on. The insects involved in mechanisms to prevent self-pollina on or
pollina on are bee, bu erfly and moth. promote cross-pollina on.
Cross-Pollina on : Cross-pollina on takes place
Stamen Anther
Pollen Grains when the pollen of one flower is transfered to
containing the s gma of another flower. This type of
sperm nuclei
pollina on helps to bring about gene c varia on
in the species and allows the plant to withstand
Flower Pollina on changes in the environment be er. Once the
Mature plant Pollen S gma
produces flowers pollen has landed on the s gma of a flower, the
Style Pollen pollen tube develops to transfer the pollen to
Ovary Tube
Fer lized egg Egg the ovules which contain the female gamete.
Seed germinates becomes the FERTILIZATION
to produce plant embryo of seed Petal
Flower The process in which the haploid male and
Plants female gametes meet and fuse together to
form a zygote is called fer liza on or syngamy.
Seeds
This can occur either outside the body known
The Process of Pollina on
as external fer liza on or inside the body
Wind known as internal fer liza on.
Wind also blows pollen grains from one flower Forma on of Seeds and Fruits
to another. But, the wind pollina on generally v The ovule developes into a seed. It contains
occurs in the flower with small or no petals stored food.

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