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Term 2 Chapter 3 | 4th Science - Plants | 4th Science : Term 2 Unit 3 : Plants

Chapter: 4th Science : Term 2 Unit 3 : Plants


After learning this lesson, students will be able to • list out the parts of leaf and their functions • explain the process of photosynthesis • describe the role of plants as a primary producer • know about green and non green plants • describe the features of flower • list out the exotic plants and their role • identify the edible part of different plants

Unit 3



Learning Objectives

After learning this lesson, students will be able to

 list out the parts of leaf and their functions

explain the process of photosynthesis

describe the role of plants as a primary producer

know about green and non green plants

describe the features of flower

list out the exotic plants and their role

identify the edible part of different plants



All living things eat food. Food helps them grow and perform daily activities. We have seen animals eating their food. But, have you ever wondered how plants get their food? Plants produce their own food with the help of chlorophyll, a pigment present in leaves. Humans and animals depend on plants for their food either directly or indirectly. Let us learn more about plants in this lesson.


I. Parts of a Leaf

Leaves are of different shapes and sizes and have different parts. However, there are some basic parts that are common in most of the leaves.

Blade : The broad flat part of the leaf (Lamina).

Apex : The tip of the leaf.

Midrib : The midrib runs along the centre of the leaf.

Veins : Veins are branch out from the midrib. They are the framework of hollow tubes that carry water and minerals.

Petiole: This part joins the leaf to the main stem.

Stomata : Stomata are tiny openings or pores mostly found at the base of the leaves. Air enters and leaves the plant through these openings. Stomata helps the plants to breathe. Stomata are used to exchange gases.

1. Leaf as food factory

Plants need food but they never depend on people or animals to provide them. Most of the plants are able to make their own food through a process called photosynthesis.

Photosynthesis = Photo (light) + synthesis (make)

Photosynthesis is a process by which plants make their food using chlorophyll water, carbon dioxide in the presence of sunlight. Let us see how this process is organized with in the plants.

Think and answer

 Which part of the leaf collects carbon dioxide?

Answer: Small pores in the leaves (Stomata)

Which part of the leaf transports water?

Answer: Veins

Water: Water is absorbed by the roots and is passed to the leaves through the tubes.

Carbon dioxide: Carbon dioxide in the air passes through small pores in the leaves.

Sunlight: A green pigment in the leaves help them to trap sunlight. This pigment is called chlorophyll. Most leaves are green in colour because of this green pigment.

Through photosynthesis plants produce the food and release oxygen into the air.

As plants prepare food for themselves and also for other living things, they are called primary producers.

Without primary producers, living things that are not capable of producing their own food and will not be able to live.

Think and answer

Why would living things not be able to live without plants?

Answer: Only plants can produce food on their own. They are primary producers. All living things depend on plants for food. So they cannot live without plants.

Try to Answer

Fill in the blanks by rearranging the letters in the bracket.

1. During photosynthesis plants releases oxygen (egxyno).

2. Plant is a primary producer (tanpl).

3. Stomata are seen in the lower (owler) surface of the leaf.

4. Pigment involved in the food synthesis is chlorophyll (phllylochor).

More to know

Plants like cactus do not have leaves. Their food is made in their green stems.

Let us do

Take two potted plants. Keep one in sunlight and other in a fully covered box. Water them regularly. After a week observe the plants.


II. Classification of Plants

Plants are classified in many ways based on stems, life span, seeds, flower and colour. In this session we will study about the classification of plants based on the flower and colour (pigment).

1. Flowering and Non-flowering plants

Flower is the most important part of many plants, because it is involved in reproduction. But some of the plants are not having flower. These plants are also reproduce in different modes. Based on this plants, can be classified into two types.

 Flowering plants

 Non-flowering plants.

Flowering plants

Plants bearing flowers are called flowering plants. It reproduce by sex cells or gametes and produce seeds. Seeds produce new plants. Eg – Mango, Neem, groundnut, paddy.

Non-flowering plants

Plants without flower that can reproduce are called non-flowering plants. These plants do not produce seeds. They reproduce by a special structure called spores. E.g. Algae, Fungi, ferns.

Let us do

List out the flowering and Non-flowering plants in your surrounding.

Flowering plants : Rose, Drumstick, Brinjal

Non-flowering plants : Conifers, Fungi, Ferns

2. Green and Non-green plants

The most important pigment present in plants are called chlorophyll. Based on the colour present in the plant, they are divided into two groups such as Green and Nongreen plants.

Green plants

Plants containing green pigments are called green plants. It looks green in colour. They prepare their own food with the help of them. It depends atmosphere, light and pigment for food preparation. Green plants are commonly called autotrophs. E.g. Grass, Paddy, Algae.

Non-green plants

Plant that lacks chlorophyll pigment and looks not green are called non-green plants. They cannot prepare their food. These plants depend on other organism for their food and living place. These are commonly called heterotrophs.

Let us do

List out the places where you see the non-green plants

1. Near dead and decaying plants.

2. Fallen logs.

Try to Answer

Fill in the blanks.

1. Algae is an example for non flowering plant.

2. Plants are classified based on pigment and flower of the plant.

3. Heterotrophs depend on other organism to live and get their food.

4. Autotrophs use carbon dioxide, sunlight and chlorophyll to prepare their own food.


III. Parts of Flower

Have you seen flowers? Try to answer the questions given below

a) Which is your favourite flower? Paneer rose

b) What is the colour of the flower? Light pink

c) How does it smell? Paneer smell

The four visible parts of a flower are explained below.

Sepal: Sepals are leaves that protect the flower while it is still a bud. Sepals are usually green in colour.

Petal: Petals are often bright coloured. Their main job is to attract insects such as bees or butterflies, to the flower. The insects help the flowers in the transfer of pollen grains.

Stamen: Stamen can be seen at the centre of a flower. They contain pollen grains that help the plants to multiply. It is the male part of a flower.

Pistil: Pistil is also seen at the centre of the flower. The pistil uses the pollen to help the flower become the fruit. It is the female part of a flower.

More to know

The largest flower in the world is Rafflesia. This rare flower is found in the rainforests of Indonesia.

Try to Answer

Fill in the blanks.

1. Sepals protect the flower while it is still a bud.

2. Stamen contains pollen grains.

3. Pistil is the female part of a flower.

Let us do

Bring few hibiscus flowers to the classroom. Distribute the flowers to children. Introduce the parts of the flower to them. Then, ask them to observe and feel the different parts of the flower and tell them to record their observation.

Petal: bright red ; Sepal: green ; Pistil: light red ; Stamen: yellow


III. Seasonal Flowers

The change in climate that occurs periodically is called seasons.

There are four general seasons - Spring, Summer, Autumn and Winter.

Most flowers bloom in a specific season. Hence, they are called seasonal flowers.

Flowers that bloom in winter

Flowers that bloom in summer

Flowers that bloom in autumn and spring

More to know

Firecracker flowers bloom in all seasons

Kurinji flower blooms once in 12 years

Think and answer: Can you name the four seasons?

Answer: Summer,  Spring, Autumn, Winter


IV. Exotic Plants

The plants that are growing outside its native area either purposefully or accidentally are called exotic plants.

Most of these plants are brought to new areas for decoration purposes. Some of them are given below.

More to know

Parthenium plant accidentally grow in a new native. This plant expands its range and disturbs the cultivation areas. The pollen of this plant is allergic in nature. So, don‛t touch this plant wherever you see.

Try to Answer

1. Find the odd one.

i. December, Tuberose, Tulip.

ii. Saffron, Dahlia, Rose.

iii. Rose, Boat lily, Crotons.

N.B : i) December and Tuberose bloom in winter.

ii) Saffron and Dahlia bloom in autumn.

iii) Boat lily and Crotons are exotic plants.

Let us do

Collect various ornamental plants and plant in your school garden or at home.


V. Plants as Food

Humans and other animals often use plants as food. Plants we eat are edible. Edible parts of some plants include leaves, stems and roots. We also eat fruits produced by plants.

Edible parts of plants

All the parts of different plants are edible, that is, we can eat them as food.

Roots as food

Many plants store excess food in their roots. They have thick and swollen roots. These roots are used as food. Some of them are given below.

Stems as food

In some plants the stem stores the excess food in it. Potato, onion, ginger are underground stems that we eat. Some of them are given below.

Leaves as food

Leaves of some plants are used as food. In some plants extra food is stored in leaves. We eat the leaves of plants like cabbage. Some of the leaves used as food are given below.

Flowers as food

Flowers are the most attractive part of the plant. Many flowers are used as food. Some of them are given below.

Fruits as food

Many fruits are used as food. Fruits are rich in vitamins and minerals. They keep us healthy. All fruits can be eaten raw.

Grains as food

Grains of pulses, cereals and pods are the commonly eaten seeds. They are rich sources of carbohydrates and proteins.

Try to Answer

Fill in the blanks.

1. Cauli flower is used as food.

2. Stem part of the potato plant is used as food.

3. Stem of the onion / ginger stores food in it.

4. Seeds are rich in carbohydrates and proteins.

More to know

Trees are the longest living organism on earth. Bamboo plants can grow upto 90cm in one day.

Let us do

Complete the table to show which parts of the plant we eat.

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