Class:5th Science। * Germination of seed *। * The embryo is the baby plant. * The plant embryo forms a hard wall around itself and is then known as a seed.
Class:5th Science
* Germination of seed *
* The embryo is the baby plant.
* The plant embryo forms a hard wall around itself and is then known as a seed.
* In order to germinate, a seed needs three things: water, air and the right temperature.
* The seed with a small roof and a small shoot is called seedling.
* Wind, water, animals and humans are the agents of seed dispersal.
* In vegetative propagation plants reproduce with the help of their roots, stems and leaves and not through seeds.
* Various stages are involved in growing healthy crops.
* Plants reproduce in two ways
(1) Reproduction from seeds
(2) Vegetative reproduction.
CONDITIONS FOR GERMINATION OF SEED
Seeds need special conditions for germination. e.g.
(1) Plenty Of Fresh Air : Seeds get oxygen to breathe from air trapped in soil. They are sown near the surface of soil.
(2) Plenty of Water : Seed absorbs water and becomes soft. It swells up and seed coat is ruptured to let the baby plant come out.
(3) Enough Sunlight And Warmth : Seeds need proper warmth for its cells to become active and grow. They do not germinate in very hot or very cold temperature.
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A. Tick(✓) the correct answer:
1. Which one is not an agent of seed dispersal?
(a) water
(b) wind
(c) plant [✓]
2. What is the other name for seed leaf?
(a) cotyledon [✓]
(b) seed coat
(c) seedling
3. Seeds with two cotyledons are called as
(a) cotyledon
(b) seedling
(c) dicots [✓]
4. The emergence of the root is typically used as the first------- that a seed is viable.
(a) indication [✓]
(b) motion
(c) Care
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B. Fill in the blanks :
[ seed, ploughing, radicle, embryo, sowing ]
1. A seed is protected by a -----------.
[embryo]✓
2. ------------ aerates the soil and allows the soil to hold moisture.
[ploughing]✓
3. The process of planting healthy seeds is known as ---------------.
[ sowing ]✓
4. The small root emerging from a germinating seed is known as-------------.
[radicle✓
5. Water, air and the right temperature are needed for ------------- to germinate.
[seed]✓
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C. Write True[✓] or False[×] :
1. Some non-flowering plants reproduce with the help of their spores.True[✓]
2. Seeds dispersed by wind must be heavy.
False[×]
3. The size of seed is important for their dispersal.True[✓]
4. Imbibition means to drink : seeds imbibe water.True[✓]
5. Coconut is dispersed by air.
False[×]
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D. Answer the following questions:
1. Define tuberous roots.
Ans: Some roots store food in them i.e. carrot, turnip, radish and sweet potato. These are swollen because of the stored food and are known as tuberous roots.
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2. Define monocotyledons.
Ans: Those seeds who have only one cotyledon is called monocotyledon.
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3. What is seedling?
Ans: The seed with a small root and a small shoot is called seedling.
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4. Write any three methods of seed dispersal.
Ans: By wind, by water and by animals or human being.
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5. What is irrigation?
Ans: Irrigation is the process of supplying water to the farming field artificially.
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6. What is the function of a cotyledon?
Ans: The seed has its own food supply, the endosperm. The cotyledon or seed leaf, absorbs the food in the endosperm and
transports this food to the embryo. The baby plant is present in between the cotyledons. It develops a new root system and shoot system that grows into a new plant.
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7. Why is seed dispersal important?
Ans: Seeds need to be dispersed because if they are not dispersed, many germinating seedlings will grow very close to the parent plant. This will result in the competition between the seedling and its parent plant. The competition is for light, space, water and nutrients. All of these are important for the growth of a young plant. Seed dispersal also creates new colonies and prevents over-crowding.
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8. How do animals help in seed dispersal?
Ans: Animals and humans eat fruits and throw away their seeds. Seeds of apple, mango, orange, etc are dispersed in this way. Some seeds have hooks that stick to the fur of animals or to the clothes of humans and get dispersed. One such example is the cocklebur seed.
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9. What are the characteristics of seeds
dispersed by wind and water?
Ans: Dispersal of Seeds by Wind
In order to be carried away by the wind, seeds to be dispersed must be light and small so that they may be carried over large
distances. They should have hair or wings to help them get carried away by the wind. The seeds of hiptage, dandelion and cotton have tufts of hair.
Dispersal of Seeds by Water
The plants need water for the dispersal of seed which grow in rivers, oceans and ponds or near water bodies. The lotus fruit has a spongy part which helps to float. Coconut is hollow on the inside and is covered with hair
outside. This makes it light and hence it can be carried by flowing water over long distances.