Seeds - Structure and Germination

Progress Check 1

Question 1

Mention whether the following statements are True (T) or False (F)

1. Plumule is the future root and radicle is the future shoot of the plant.
2. Micropyle serves for the emergence of the radicle.
3. Cotyledons in castor are a big store of food for the embryo.
4. Maize grain has a large endosperm.
5. Tegmen is the outermost layer of the seed.

Answer

1. False
   Corrected statement — Plumule is the future shoot and radicle is the future root of the plant.
2. True
3. False
   Corrected statement — Endosperm in castor are a big store of food for the embryo.
4. True
5. False
   Corrected statement — Testa is the outermost layer of the seed.

Progress Check 2

Question 2

Fill in the blanks by choosing the correct alternative

1. In a dry seed, the embryo is in ............... state. (active/quiescent)
2. Water is absorbed by the seed mainly through ............... . (entire surface/micropyle)
3. Very low temperature ............... the growth of embryo. (inhibits/destroys)
4. Germination in Pea is ............... . (epigeal/hypogeal)
5. Coleoptile is a part found in the germinating ............... . (castor/maize)
6. Alkaline pyrogallic acid is used for absorbing ............... during experiments on germination. (oxygen/carbon dioxide)

Answer

1. In a dry seed, the embryo is in quiescent state.
2. Water is absorbed by the seed mainly through micropyle.
3. Very low temperature inhibits the growth of embryo.
4. Germination in Pea is hypogeal.
5. Coleoptile is a part found in the germinating maize.
6. Alkaline pyrogallic acid is used for absorbing oxygen during experiments on germination.

Multiple Choice Type

Question 1

Which one of the following plant parts is correctly matched with one of its stated characteristic?

1. Mango seed → aleurone layer
2. Bean seed → endosperm
3. Maize grain → coleoptile
4. Wheat grain → exalbuminous

Answer

Maize grain → coleoptile

Reason — Protective sheath enclosing the plumule in monocots like maize is called coleoptile.

Question 2

Seeds sown very deep in the soil fail to germinate because they

1. cannot exert enough force to push the soil upward.
2. do not get enough sunlight.
3. get too much water.
4. do not get enough oxygen.

Answer

do not get enough oxygen & cannot exert enough force to push the soil upward.

Reason — Seeds sown very deep in the soil fail to germinate because of two main reasons:

1. No proper supply of oxygen (for respiration).
2. Insufficient pushing force in the embryonic parts (hypocotyl and epicotyl) to break through the upper layers of soil.

Question 3

Fruit is a ripened :

1. Ovary
2. Embryo
3. Ovule
4. Zygote

Answer

Ovary

Reason — After fertilization the ovary grows to form fruit.

Question 4

Which of the following is the largest seed ?

1. Watermelon
2. Pumpkin
3. Double coconut
4. Mango

Answer

Double coconut

Reason — Double coconut has largest seed.

Question 5

The distinct whitish oval scar on the concave side of the seed is termed as :

1. Scutellum
2. Micropyle
3. Hilum
4. Germpore

Answer

Hilum

Reason — Hilum is the distinct whitish oval scar on the concave side of the seed which represents the spot where the ovule was attached to ovary wall.

Question 6

The single cotyledon of a maize grain is called:

1. Hypocotyl
2. Scutellum
3. Coleorhiza
4. Embryo

Answer

Scutellum

Reason — The single cotyledon of a maize grain is called Scutellum.

Question 7

The outermost hard brownish layer of the seed coat is:

1. Testa
2. Tegmen
3. Epicotyl
4. Aleurone layer

Answer

Testa

Reason — Seed coat consists of outermost hard brownish layer known as testa and inner layer tegmen.

Question 8

The part of an embryo which develops into root is

1. Coleorhiza
2. Plumule
3. Coleoptile
4. Radicle

Answer

Radicle

Reason — Radicle develops to form root.

Question 9

Which of the following statement holds true for a maize grain?

1. The maize grain is a ripened ovary containing a single seed.
2. The fruit wall and seed coat are fused together.
3. The outermost layer of the endosperm is rich in protein.
4. All of the above.

Answer

All of the above

Reason — Maize is monocot with fruit wall and seed coat fused together.

Question 10

The kind of germination in which the cotyledons remain underground is :

1. Viviparous germination
2. Epigeal germination
3. Vegetative germination
4. Hypogeal germination

Answer

Hypogeal germination

Reason — When epicotyl elongates, the cotyledons remain underground. This type of germination is known as Hypogeal germination.

Very Short Answer Type

Question 1

Correct the following false statements by changing the first/last word only.

(a) Plumule develops into the root system.

(b) Testa is the thin inner layer of the seed coat.

(c) Endothelium separates the endosperm and embryonic region in the maize grain.

(d) Hypocotyl elongates faster in hypogeal germination.

(e) Germination is the period of rest in a seed.

Answer

(a) Plumule develops into the shoot system.

(b) Tegmen is the thin inner layer of the seed coat.

(c) Epithelium separates the endosperm and embryonic region in the maize grain.

(d) Epicotyl elongates faster in hypogeal germination.

(e) Dormancy is the period of rest in a seed.

Question 2

Name the following:

(a) A monocotyledonous endospermic seed.

(b) A chemical used in experiments which absorbs oxygen.

(c) Part of the plumule above the embryonic axis of the seed.

(d) A plant which shows viviparous germination.

(e) The layer of endosperm of maize rich in protein.

(f) A seed with folded plumule leaves.

Answer

(a) Maize

(b) Pyrogallic acid

(c) Shoot

(d) Rhizophora

(e) Aleurone layer

(f) Bean

Question 3

Fill in the blanks:

(a) In bean seeds, ............... grows faster and the seeds are brought ............... ground.

(b) ............... is a protective layer of radicle and ............... protects the rolled plumule.

(c) A seed is protected by ............... and................

(d) Seeds absorb water through ............... which also helps in diffusion of respiratory gases.

(e) Rice, wheat and maize are rich in ............... food.

Answer

(a) In bean seeds, hypocotyl grows faster and the seeds are brought above ground.

(b) Coleorhiza is a protective layer of radicle and coleoptile protects the rolled plumule.

(c) A seed is protected by testa and tegmen.

(d) Seeds absorb water through micropyle which also helps in diffusion of respiratory gases.

(e) Rice, wheat and maize are rich in starch food.

Question 4

Arrange the following set of terms in order, so as to be in logical sequence. Rewrite the correct order.

(a) Embryo, 1st male gamete, zygote, egg cell, micropyle.

(b) Zygote, embryo, seed, allogamy, fusion of gametes.

(c) Seed coat bursts, hypocotyl elongates, radicle grows downward, hypocotyl forms loop above the soil, epicotyl elongates.

Answer

(a) Micropyle, 1st male gamete, egg cell, zygote, embryo.

(b) Allogamy, fusion of gametes, zygote, embryo, seed.

(c) Seed coat bursts, radicle grows downward, hypocotyl elongates, hypocotyl forms loop above the soil, epicotyl elongates.

Question 5

Give two examples of each of the following :

(a) Monocot albuminous seed.

(b) Dicot albuminous seed.

(c) Monocot non-endospermic seed.

(d) Dicot non-endospermic seed.

(e) Viviparous plant.

Answer

(a) Cereals, millets

(b) Poppy, custard apple

(c) Vallisneria, orchids

(d) Pea, Gram

(e) Rhizophora, Sonneratia

Question 6

Match the terms given in column A with those of column B.

Answer

Question 7

Name the following:

(a) Two types of seeds on the basis of the number of cotyledons.

(b) Two types of seeds on the basis of endosperm.

(c) Three necessary conditions for the germination of seeds.

(d) Two main types of germination.

(e) Two layers of the seed coat.

Answer

(a) Monocots, Dicots

(b) Albuminous, Exalbuminous

(c) Water, Suitable temperature, Oxygen

(d) Epigeal, Hypogeal

(e) Testa, Tegmen

Short Answer Type

Question 1

Define the following terms:

(a) Seed

(b) Fruits

(c) Grain

(d) Dormancy

(e) Germination

Answer

(a) Seed — A ripened ovule, which contains embryo and has capacity to develop into a new plant is called Seed.

(b) Fruits — Enlarged and ripened ovary is called Fruit.

(c) Grain — A fruit in which the fruit wall and the seed coat is fused to form a protective layer is called Grain.

(d) Dormancy — A period of rest when the embryo is inactive inside the seed, is called Dormancy.

(e) Germination — The process of formation of a seedling from embryo is called Germination.

Question 2

What is the difference between an embryo and a seed?

Answer

Question 3

Germinated grams are considered highly nutritive. What is the reason for this belief?

Answer

Germinated grams are considered highly nutritive because the cotyledon of the seed absorbs food from the endosperm, making it nutritive. It is rich in starch and its outermost layer is rich in protein.

Question 4

Why do we not use the terms maize fruit and maize seed? What do we say instead?

Answer

A fruit is a fertilised ovary and a seed is a fertilized matured ovule which contains an embryo or a growing plant. Maize grain is actually a fruit in which the fruit wall and the seed coat are fused together to form a protective layer. Therefore, we do not use the terms maize fruit and maize seed. Instead, we call such fruits as grains.

Long Answer type

Question 1

Distinguish between the following pairs :

(a) Monocotyledonous and Dicotyledonous seeds

(b) Epicotyl and Hypocotyl

(c) Epigeal and Hypogeal germination

(d) Radicle and Plumule

(e) Albuminous and Exalbuminous seeds

Answer

(a) Difference between Monocotyledonous and Dicotyledonous seeds:

(b) Difference between Epicotyl and Hypocotyl:

(c) Difference between Epigeal and Hypogeal germination:

(d) Difference between Radicle and Plumule:

(e) Difference between Albuminous and Exalbuminous seeds:

Question 2

What are the functions of the following in a seed?

(a) Seed coat

(b) Micropyle

(c) Cotyledons

(d) Radicle

(e) Plumule

Answer

(a) Seed coat — A seed coat protects the delicate inner parts of the seed from injury and from the attack of bacteria, fungi and insects. It also plays a crucial role in regulating seed dormancy. The seed coat prevents premature germination by providing a barrier that restricts water and gas exchange.

(b) Micropyle — It serves two functions:

1. When soaked in water, the seeds absorb water mainly through the micropyle and make it available to the embryo for germination.
2. It provides for the diffusion of respiratory gases for the growing embryo.

(c) Cotyledons — Cotyledons contain food for the embryo and protect it.

(d) Radicle — Radicle is the embryonic root of the plant. It grows downward into the soil and anchors the plant, absorbing water and nutrients from the ground. It develops into the primary root of the plant, which later gives rise to the entire root system.

(e) Plumule — Plumule is the embryonic shoot of the plant. It grows upwards and is responsible for the development of the above-ground parts of the plant, including stems, branches, and leaves.

Question 3

Suggest an experiment to prove that a suitable temperature is necessary for germination.

Answer

Aim — To prove that a suitable temperature is necessary for germination.

Apparatus — Two beakers, wet cotton wool, refrigerator

Procedure —

(1) Take two beakers and label them as A and B.

(2) Place some gram seeds on wet cotton wool in each of the beakers.

(3) Keep beaker A at ordinary room temperature and beaker B in the refrigerator.

(4) In 1-2 days, the seeds in beaker A will germinate, showing the importance of a suitable temperature for germination. Seeds in beaker B may not show the signs of germination or may germinate after several days, though not to the extent as the seeds in beaker A.

Inference — Seeds require a suitable temperature for germination.

Question 4

Sometimes the potatoes kept in a basket during the late rainy season start giving out small shoots. Would you call it germination? Give reason in support of your answer.

Answer

Yes, we call it germination because all the changes leading to the formation of a seedling collectively constitute germination. During germination, either the epicotyl or the hypocotyl elongates.

Question 5

Give two differences in each of the following pairs:

(a) Coleorhiza and coleoptile

(b) Bean seed and maize grain

(c) Germination and vivipary

Answer

(a) Two differences between Coleorhiza and Coleoptile:

(b) Two differences between Bean seed and Maize grain:

(c) Two differences between Germination and vivipary:

Question 6

Justify the statement that the maize grain is a 'one seeded fruit'.

Answer

A fruit is the enlarged ripened ovary in which the ovarian wall forms the fruit wall and encloses the seed. The fruit protects the seed and helps in seed dispersal. The maize grain is regarded as a 'one-seeded fruit' because the fruit wall and the seed coat are fused to form a protective layer. Such a fruit is called grain.

Question 7

What is the role played by the hypocotyl in epigeal germination?

Answer

Germination of a seed which takes place above the ground is called epigeal germination. In epigeal germination, the hypocotyl grows forming a loop above the soil. It then straightens pushing the cotyledons above the ground.

Question 8

Draw a neat and labelled diagram of :

(a) A twig of viviparous plant showing its germination.

(b) A seedling growing in soil.

Answer

(a) Diagram of a twig of viviparous plant showing its germination:

(b) Diagram of a seedling growing in soil:

Question 9

Draw a neat and labelled diagram of the 'Experimental set-up of three-bean seed experiment' and mention the necessity of each condition for the germination of seeds.

Answer

Experimental set-up of three-bean seed experiment is shown in the diagram below:

The observations of the three-bean seed experiment are as follows:

1. The middle seed germinates. It gets both oxygen and water.
2. The top seed does not germinate at all. It gets only oxygen but no water.
3. The bottom seed does not germinate or stops germinating after the emergence of a small radicle. It gets water but very little oxygen (from the air dissolved in water).

Water, suitable temperature and air (oxygen) are necessary for germination.

1. Water — Water is necessary because:
   1. By absorbing water, the seed swells and consequently the seed coat ruptures allowing the elongating radicle to come out and form the root system.
   2. Water is essential for chemical reactions and enzyme action on stored food in cotyledons or endosperm, converting it into a diffusable (dissolved) form for the developing embryo.
2. Suitable temperature — A moderately warm temperature (25°C to 35°C) is usually favourable for germination which is also called optimum temperature. A very low temperature inhibits the growth of the embryo and a very high temperature destroys its delicate tissues.
3. Oxygen — Oxygen is needed for respiration that provides energy for the rapid cell division and cell growth during germination.

Structured/Application/Skill type

Question 1

The figure shown below represents the internal structure of a certain seed. Study the figure and answer the following questions.

(a) Identify the seed and mention whether it is mono or dicotyledonous.

(b) Label the guidelines 1 to 4.

(c) Write an important role of part 2.

(d) Mention the food component found in part 4.

(e) What kind of germination takes place in the above mentioned seed ?

Answer

(a) It is a Bean seed that is dicotyledonous.

(b) The labelled guidelines are:

• 1 → Plumule
• 2 → Radicle
• 3 → Testa
• 4 → Cotyledons

(c) Radicle grows downward into the soil and anchors the plant, absorbing water and nutrients from the ground. It develops into the primary root of the plant, which later gives rise to the entire root system.

(d) Protein

(e) Epigeal germination

Question 2

With regard to germination in bean seed, answer the following questions:

(a) State the function of the 'Micropyle'.

(b) Name the part of the seed that grows into the seedling.

(c) Name the part of the seed that provides nutrition for the growing seedling.

(d) Draw a neat labelled diagram of a mature bean seed.

Answer

(a) The 'Micropyle' serves two important functions:

1. Allows absorption of water and makes it available to the embryo for germination.
2. Enables diffusion of respiratory gases for the growing embryo.

(b) The embryo of the seed grows into the seedling.

(c) The cotyledons of the seed provide nutrition for the growing seedling or the embryo.

(d) Below is the diagram of a mature bean seed: