More about Plants

Unit

1

Recognise the different •ways by which plants reproduce

Identify the seed structure and •study the conditions required for seed germination

Learn the different ways of seed •dispersal

Distinguish between different kinds •of crops

Know about the different stages of •agriculture

1

1. Match the fruits with the number of seeds they have.

ipapaya

vapple

ivmango

iiiguava

iiorange

aone seed

bfew seeds

cmany seeds

Aim: To study the structure of a seed

You will need: kidney bean (Rajmah) seeds, cotton, shallow dish, and water

1 What to do: Bring some kidney bean seeds to class. Try to split a seed with your hands. You cannot do it because it is hard. Now, put the seeds in moist cotton and place them in a shallow dish for a day. Take out a seed and observe it carefully.

1 You will see: The seed is soft as it has absorbed water. It has a small hole through which water is absorbed. Right below the hole is a scar. This is where the seed was attached to the fruit.

2 What to do: Remove the thin outer covering of the seed. This is the seed coat that protects the baby plant.

2 You will see: You can see two seed leaves. These are called cotyledons. They store food and provide nourishment to the germinating seedlings. Between the cotyledons is the baby plant, called the embryo. It has two parts, the baby shoot and the baby root. The baby shoot grows upwards and gives rise to stem, leaves, and flowers. The baby root grows downward into the soil to form the roots of the plant.

REPRODUCTION IN PLANTSWe see many kinds of plants around us. What makes plants increase in number—by the process of reproduction. Plants mainly reproduce in two ways:

some plants reproduce through seeds.•some plants reproduce through their body parts such as stems, leaves, or roots.•

Reproduction from Seeds

Most plants grow from seeds. A plant produces many seeds. But all these seeds do not grow into new plants. Some are eaten by birds and animals while some get destroyed by rain or extreme heat. Some seeds are not able to develop into plants due to insufficient air, moisture, or sunlight. Let us study the structure of a seed.

seed coat

embryo

baby shoot

baby root

seed structure iKidney bean seed i

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Germination of Seeds: You know that a plant produces many seeds. But only a few of them are used for germination. Germination is the process by which a seed produces a baby plant or seedling in the presence of water, air, and warmth of sunlight. Let us study the conditions required for a seed to germinate.

•   Seeds of some plants such as grams have two cotyledons. They are called dicot seeds.

•   Seeds of some plants such as rice and maize have one cotyledon. They are called Monocot seeds. 

BitsInfo

Aim: To study the conditions required for seed germination

You will need: kidney bean seeds, cotton, shallow dishes and water

What to do: Take four shallow dishes. Place cotton in each dish. Take a few seeds and put some on each dish. Now, follow the given steps for each dish.

Dish 1: Keep this dish in a place where it gets adequate air and sunlight. The cotton should be moist.

Dish 2: Place the second dish in the refrigerator and keep the cotton moist.

Dish 3: Place it where it can get adequate air and sunlight. Do not wet the cotton.

Dish 4: Place it where it can get adequate sunlight. Keep the seeds and the cotton covered with water.

You will see: Observe the four dishes for a few days. Note down your observations. In which dish have the seeds started germinating?

Dish 1

Dish 2

Dish 3

Dish 4

stages of seed germination i

cotyledons

first leaf

Root

shoot

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The baby root grows down into the soil and forms the root. The baby shoot grows up off the soil to form stem, flowers, etc. Thus, you see that all seeds need adequate air, water, and sunlight to germinate. If any one condition is missing, the seeds will not grow into healthy plants.

Seed Dispersal

What is the total number of students in your class? …………………………………………

What if many students from the next class were also asked to sit in your classroom? Would everyone get a seat? …………………………………………

If too many seeds are sown too close to each other, they will not be able to germinate. There will be a struggle for food, water, and sunlight.

Seeds need adequate sunlight, air, and water to grow into healthy plants. That is why nature helps in scattering the seeds and ensures that they do not grow too close to each other. The process by which seeds are scattered away from the mother plant is called seed dispersal.

Seeds are dispersed in different ways. They may be carried to far-off places by wind, water, or animals. These are called agents of dispersal. Some plants also expel their seeds explosively. Seed size is an important factor that determines how the seed is dispersed.

Dispersal by wind: Seeds that are small and light in weight, are usually dispersed by wind. Cotton and dandelion seeds have fine, long hair around them. So they are easily carried away by the wind. Some seeds have structures like wings which help them to float in the air. Seeds of plants like drumstick, jacaranda, and maple have wings.

The seeds of the sycamore have wings which spin through the air like mini helicopters. Such seeds

get dispersed by wind easily.

Dispersal by water: The seeds of plants that grow in or near flowing water are generally dispersed by water. The lotus fruit is spongy and floats easily. Coconut has air trapped between its fibres which helps it to float and is dispersed by water.

dispersal by wind i

dandelion seeds maple seeds

Wing

dispersal by water (coconut) i

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Dispersal by explosion: The fruits of pea, geranium, gorse pod, poppy, and balsam burst open when they ripen. The seeds pop out and are scattered.

•   Guava seeds are dispersed through ingestion by animals. This method is called endozoochory. The edible nutritious fruit is eaten by the animals while the seeds are excreted out.

•   Seeds which get attached to our clothes or to the fur of animals are called burs. These seeds have small hooks which cling to the tiny loops in our clothes.

BitsInfo

Dispersal by animals: After eating litchi, peach, papaya, orange, and other fruits, we throw away the seeds. When these seeds fall on the ground, they germinate. In this way, we help in their dispersal.

When birds and animals eat fruits, the seeds come out as droppings. These seeds germinate in places far away from the plant.

Some seeds like Xanthium have hooks or spines. They stick to our clothes or to the skin of animals. They then get dispersed to distant places.

poppy

seeds with hooks

dispersal by animals i

xanthium

geranium

pod closed

explosion of seeds

dispersal by explosion` i

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Reproduction through Body Parts

Many plants reproduce from stems, leaves, or roots.

Reproduction from stem: New plants are also grown from stems. The stems are taken from the mother plants that have buds on them. New plants grow from these buds. Plants such as rose, bougainvillea, hibiscus, and sugarcane are grown this way.

rose plant the stem is cut the cut portion of the stem is planted

reproduction from stem i

Sweet potato is an underground stem that has buds known as eyes. These buds can grow into new plants. Onion and ginger too grow from stem. A1

Reproduction from leaves: Some plants reproduce from their leaves. The leaves of Bryophyllum are thick and fleshy, and also have many buds along their edges. New plants grow from these buds.

Reproduction from roots: Sweet potato and carrot are roots that have been modified to store food. When replanted, these roots grow into new plants.

reproduction from leaf—Bryophyllum i

bud

sweet potato i

bud

sweet potato plant

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Reproduction from Spores: You know that certain plants do not bear flowers and seeds. How do they reproduce? They have special structures called spores that help in reproduction. If you look at the underside of a fern leaf, you will see many dark-coloured dots. These are called sori. Rub these between your thumb and forefinger. The powdery substance that can be felt between your fingers are called spores.

Fungi, such as bread mould, also reproduce by spores.

Question Drill

1. State whether the following statements are TRUE or FALSE.

a. Fungi reproduce from roots.

b. Potato is an underground stem.

c. The baby plant between the cotyledons is called the embryo.

d. The thin outer covering of a seed is the seed leaf.

e. The seeds of balsam are dispersed by explosion.

Aim: To study the process of reproduction by a root

You will need: carrots, shallow dish, and water

What to do: Cut off the top portion of a carrot that has leaves. Place it in a shallow dish with the cut end facing downwards. Pour water into the dish such that half of the cut carrot is dipped in water. Keep this dish in a place where it will receive enough sunlight. Observe after a few days.

You will see: A new plant would have grown from the carrot top.

reproduction by spores i

sori

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wheat i

sowing of rice i

CROPSPlants that are grown in large quantities to provide food and other useful substances are called crops. This practice of growing large quantities of plants for food and other purposes is called agriculture.

Kinds of CropsCrops are of different kinds:

food crops• , such as wheat, rice, potato, and sugarcane

fibre crops• , such as cotton, jute, and hemp

oil-producing crops• , such as mustard, sunflower, and soyabean

To grow properly, all crops require sunlight, water, air, and fertile soil that provides all the nutrients. Some crops, however, may require one of these in a greater or lesser amount. So, they are grown in different seasons and in different areas.

In India, crops that are grown in the summer season are called kharif crops. Rice, jowar, bajra, jute, hemp, peanut, millet, maize, and pulses are kharif crops. Vegetables such as spinach, brinjal, tomato, onion, pumpkin, garlic, and gourd grow well in the summer season. Peach, litchi, mango, watermelon, muskmelon, plum, and apricot are some fruits that grow best in summer.

Crops that are grown in winter are called rabi crops. Wheat and gram are rabi crops. Radish, turnip, carrots, peas, mustard, cauliflower, cabbage, and beans are some vegetables that grow well in winter. Apple, orange, and pomegranate are fruits that are grown generally in the winter season.

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Healthy Crops: Crops need proper care so that they can produce better yield. Here are some tips for growing healthy crops.

The crop to be grown should be selected after considering the kind of soil in the area. For •example, rice grows well in wet, clayey soil, but groundnut needs porous, sandy soil.

Time to time, manure and fertilisers should be added to the soil in sufficient quantities. •This would make the soil fertile.

The seeds sown should be of good quality. Also, seeds should not be planted too close to •each other or too deep in the soil.

Adequate water should be provided at different stages of the growth of plants.•

Crops should be sprayed with • insecticides and pesticides to keep them free from pests, diseases and harmful animals.

Weeding, that is, removal of unwanted plants should be done regularly.•

Stages of Agriculture

1

4 5 6

2 3

The field is ploughed and manure is added to the soil. After this, the seeds are sown.

The field is irrigated. To protect the crops, they are sprayed with pesticides. The crops are then harvested.

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seed coat: thick covering of a seed that protects the baby plant

cotyledons: the seed leaves that contain food for the baby plant

embryo: the baby plant

germination: the process by which a seed develops into a baby plant in the presence of water, air, and sunlight.

seed dispersal: the process by which seeds are scattered away from the mother plant

crops: plants that are grown in large quantities to provide food and other useful substances

agriculture: the practice of growing large quantities of plants for food and other purposes

kharif crops: crops grown in the summer season

rabi crops: crops that are grown in winter

insecticides: chemicals used for destroying harmful insects

pesticides: chemicals used to destroy harmful pests (insects or animals)

irrigate: supply with water

harvest: to gather a crop

WORD

Plants can reproduce from seeds and from their body parts such as •stems (eg: potato), leaves (eg: Bryophyllum), or roots (eg: carrot).

Seeds need adequate air, water and sunlight for germination.•

Seeds are scattered so that they do not grow too close to each other.•

Seeds are dispersed by wind (eg: maple seeds), water (eg: coconut), •animals (eg: Xanthium) or by explosion (eg: pea).

There are three main types of crops—food crops (eg: wheat), fibre •crops (eg: cotton) and oil-producing crops (eg: mustard).

Different crops need different conditions for growing. Rice, jowar •and bajra are examples of kharif crops. They grow in summer season. Wheat and gram are rabi crops. They grow in the winter season.

Crops need to be given proper care so that they can produce •better yield.

inow

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Review Zone

A Choose the most suitable word from the following to fill in the blanks.

kharif seeds rabi fibre food spongy

1. Most plants reproduce from ...............................

2. The lotus fruit is ........................ and so it floats easily.

3. Rice and millet are ............................ crops.

4. Mustard is a .................................. crop.

5. Cotton is a .................................. crop.

B State whether the following statements are TRUE or FALSE.

1. All seeds grow into new plants. .........................................

2. To germinate, seeds require only water. .........................................

3. Papaya seeds are usually dispersed by wind. .........................................

4. Jute is a fibre crop. .........................................

5. Manures and fertilisers are good for the soil. .........................................

C Complete the crossword with the help of the given clues.

ACROSS

4. the scattering of seeds to different places

5. seeds pop and scatter

6. an agent of dispersal

8. this is added to make the soil fertile

DOWn

1. seed leaves inside the seed coat

2. growing of a baby plant from a seed

3. winter crops

7. summer crops

1

3

4

6 7

2

5

8

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D How are these seeds dispersed? Tick(3) the correct option.

1. coconut wind water animal explosion

2. drumsticks wind water animal explosion

3. peas wind water animal explosion

4. jacaranda wind water animal explosion

5. mango wind water animal explosion

E Answer the following questions.

1. What is germination? Name the conditions required for it.

2. Name the different ways of plant reproduction with examples.

3. What are agents of dispersal? Why is dispersal of seeds necessary?

4. What is the difference between seed dispersed by wind and seed dispersed by an animal?

5. Name some plants which disperse their seeds by explosion.

6. What is the difference between kharif and rabi crops? Give two examples of each.

7. Why should plants be sprayed with insecticides and pesticides?

8. Write a short note on the stages of agriculture.

HoTS CoRneR

1. Why do plants grow better in soil than in sand?

2. Apple trees do not grow in Kerala and cononut cannot be grown in Kashmir. Why?

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enHanCe youR Life SkiLLS

1. Germinate a few maize seeds and pea seeds in two different pots. Observe them everyday. Draw your observations on a chart. What is the difference in the way they germinate?

2. Sprout moong dal. Keep the dal in water for 8 hours in a dish. Drain the water and hang the dal in a wet muslin cloth. Ensure that the cloth remains moist by sprinkling water time to time. Keep it for 24 hours to get moong sprouts. Add diced tomatoes and onions to it. Sprinkle salt and squeeze some lime juice over it. Eat a yummy, healthy snack.

onLy a CLiCk away

1. To view an animation on seed dipersal, you can visit the link: http://www2.bgfl.org/bg fl2/custom/resources_ftp/client_ftp/ks2/

science/plants_pt2/dispersal.html2. To learn how to make a bonsai plant, you can visit the following link. http://www.youtube.com/watch?v=viFAugK_41c

aCTiviTy Bag

1. Reproduction from Stem

You will need: potato, cotton and water What to do: Take some moist cotton and wrap a potato in it.

Keep the cotton moist for a few days. Keep in a warm place. You will see: You will see buds appearing on some parts of the potato. If you keep this

potato in a warm place for a few more days, you will notice that the buds will grow leaves. Note: Now if you place the potato and the moist cotton in a refrigerator, you will observe

that the growth of leaves stops.

Teacher’s NotesTeacher can bring different kinds of seeds to class. Let students observe them carefully. Use two or three types •of seeds to show germination. Ask students to observe the seeds at different intervals to see the formation of different structures during the process of germination.Bring different fruits to class. Discuss with students how the seeds of those fruits are dispersed.•If possible, visit a plant nursery to let students observe the modes of reproduction in plants.•Answers to Question Drill: 1. • a. False; b. True; c. True; d. False; e. False.

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