Seeds - Structure and Germination

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 is a big store of food for the embryo.
4. True
5. False
   Corrected statement — Testa is the outermost layer of the seed.

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.

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.
Mango is a dicot, non-endospermic seed and does not have an aleurone layer.
Bean is a dicot, exalbuminous seed.
Wheat is a monocot, albuminous seed.

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.

Reason — The best answer among the given options is that seeds do not get enough oxygen. Seeds sown very deep in the soil fail to germinate mainly due to lack of oxygen for respiration. They may also fail because the embryonic parts, such as the hypocotyl and epicotyl, may not have sufficient force to break through the upper layers of soil.
Sunlight is not required for germination, and deep soil usually does not harm seeds because of excess water alone.

Fruit is a ripened:

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

Answer

Ovary

Reason — After fertilization the ovary grows to form fruit.
The embryo develops from the zygote inside the seed. It becomes a new plant, not the fruit. The ovule becomes the seed after fertilization, not the fruit. The zygote develops into the embryo, not directly into fruit.

Which of the following is the largest seed?

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

Answer

Double coconut

Reason — Double coconut produces the largest seed.
Watermelon seeds are relatively small and flat. Even though the fruit is large, the seeds are not. Pumpkin seeds are larger than many common seeds, but they are still much smaller than the largest known seeds. Mango has a single large seed inside, but it is still much smaller than the double coconut seed.

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 the ovary wall.
The scutellum is a structure of the embryo in monocot seeds. The micropyle is a tiny pore in the seed coat through which water enters during germination. It is not the whitish oval scar. Germpore is not a standard botanical term used for seed structure in this context.

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.
The hypocotyl is the part of the embryo axis between the cotyledons (or cotyledon and radicle). It is not a cotyledon itself. The coleorhiza is a protective sheath covering the radicle in monocot seeds like maize. The embryo is the whole young plant inside the seed, which includes cotyledon, radicle, plumule, etc., not just the cotyledon.

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.
The tegmen is the inner layer of the seed coat, lying just below the testa. It is usually thinner and softer. The epicotyl is part of the embryo axis above the cotyledons. It develops into the shoot, not part of the seed coat. The aleurone layer is the outer layer of the endosperm in cereal grains like wheat and maize.

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.
The coleorhiza is a protective sheath around the radicle in monocot seeds. It does not itself develop into the root; it only protects it. The plumule develops into the shoot, not the root. The coleoptile is a protective sheath covering the plumule in monocots. It helps the shoot emerge through soil.

Which of the following statements 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.
Maize grain is a caryopsis, a type of dry fruit in which the ovary wall develops into the fruit wall and encloses a single seed. In maize, the pericarp (fruit wall) and seed coat (testa) are completely fused, forming a single protective covering. The outermost layer of the endosperm, called the aleurone layer, is rich in protein and helps during germination.

Seema observed different kinds of seeds which can be categorised on the basis of certain features like cotyledons, endosperm, etc. She recorded her observations as follows :

P- Seeds are dicotyledonous and exalbuminous.

Q- Seeds are monocotyledonous and albuminous.

R- Cotyledons are rich in protein.

S- Stored food material is rich in starch.

Which of her above observations match with bean seeds?

1. R and Q
2. Q and S
3. S and P
4. P and R

Answer

P and R

Reason — Bean seeds are dicotyledonous and non-endospermic. Bean seeds store food mainly in cotyledons, which are rich in proteins.

Seeds germinate in two ways. The type in which the cotyledons remain underground is called (P) ............... germination. During this type of germination, the (Q) ............... elongates faster.

1. P — Epigeal, Q — Hypocotyl
2. P — Epigeal, Q — Epicotyl
3. P — Hypogeal, Q — Epicotyl
4. P — Hypogeal, Q — Hypocotyl

Answer

P — Hypogeal, Q — Epicotyl

Reason — In hypogeal germination, the cotyledons remain below the ground. The epicotyl elongates faster, pushing the plumule above the soil.
The epicotyl elongates faster, pushing the shoot upwards. In epigeal germination, the hypocotyl elongates.

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.

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

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) Maize, wheat

(b) Poppy, custard apple

(c) Vallisneria, orchids

(d) Pea, gram

(e) Rhizophora, Sonneratia

Given below is the longitudinal section of a maize grain. Match the structures marked (a) to (e) with their correct functions/characteristics.

Example: (f)-6: Separates the endosperm and the embryonic part.

Answer

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 the 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 starchy food.

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) Tegmen, Embryonic axis, Cotyledons, Testa
(arrange with respect to their position in a seed from outer to inner)

Answer

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

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

(c) Testa, Tegmen, Cotyledons, Embryonic axis.

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

Answer

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

Define the following terms:

(a) Seed

(b) Fruits

(c) Grain

(d) Dormancy

(e) Germination

Answer

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

(b) Fruit — The enlarged and ripened ovary is called a fruit.

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

(d) Dormancy — The period of rest when the embryo remains inactive inside the seed is called dormancy.

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

What is the difference between an embryo and a seed?

Answer

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

Answer

Germinated grams are considered highly nutritive because germination activates enzymes that break complex starch and proteins stored in the cotyledons of the gram seed into simpler, easily digestible forms.

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.

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:

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.

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.

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

No, this is not called germination. It is an example of vegetative propagation. Germination is the process of formation of a seedling developed from the embryo. In this case, the potato tuber is a modified stem, and the small shoots (called sprouts or eyes) grow directly from it without involving seeds.

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:

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.

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.

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:

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.

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

Kiara visited a forest with marshy land. She observed that in some of the plants, the seeds germinate inside the fruit while still being attached to the parent plant. A part of the plant and a seedling are shown below in the diagram, answer the questions that follow.

(a) What kind of germination is shown above in the figure?

(b) Give two examples of the plants which germinate by this kind of germination.

(c) Mention the part shown in the figure as 'A'.

Answer

(a) Viviparous germination

(b) Rhizophora and Sonneratia

(c) Hypocotyl

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:

Assertion (A): Fruit is the enlarged ripened ovule which protects the seeds.

Reason (R): Fruits develop from the ovary of the pistil after the process of pollination and fertilization. Ovarian wall forms the pericarp.

1. Both A and R are true and R is the correct explanation of A.
2. Both A and R are true but R is not the correct explanation of A.
3. A is true but R is false.
4. A is false but R is true.

Answer

A is False but R is True.

Reason — A is False as fruit is the enlarged ripened ovary, not the ovule.
R is True because after pollination and fertilization, the ovary of the pistil develops into the fruit. The ovary wall becomes the pericarp (fruit wall).

Therefore, A is False but R is True is the correct option.

Assertion (A): Dicotyledonous seeds are always exalbuminous (non-endospermic).

Reason (R): All dicotyledonous seeds contain two cotyledons which store food material for the developing embryo.

1. Both A and R are true and R is the correct explanation of A.
2. Both A and R are true but R is not the correct explanation of A.
3. A is true but R is false.
4. A is false but R is true.

Answer

A is False but R is True.

Reason — A is False because both monocotyledonous and dicotyledonous seeds can be exalbuminous. Vallisneria and Orchids are examples of monocotyledonous exalbuminous seeds while gram and pea are examples of dicotyledonous exalbuminous seeds.
R is True as dicotyledonous seeds contain two cotyledons storing food material.

Therefore, A is False but R is True is the correct option.

Assertion (A): Micropyle is the opening through which the pollen tube enters the ovule.

Reason (R): Micropyle helps in the diffusion of respiratory gases for the growing embryo.

1. Both A and R are true and R is the correct explanation of A.
2. Both A and R are true but R is not the correct explanation of A.
3. A is true but R is false.
4. A is false but R is true.

Answer

Both A and R are true but R is not the correct explanation of A.

Reason — A is true as the micropyle is a small opening in the ovule through which the pollen tube enters during fertilization.
R is true as after fertilization, the micropyle remains as a tiny pore that allows the entry of water and oxygen, helping in the respiration of the growing embryo.

Therefore, Both A and R are true but R is not the correct explanation of A is the correct option.

Assertion (A): The single cotyledon of maize grain is termed as scutellum which does not store any food material for the developing embryo.

Reason (R): Food material for the developing embryo is stored in the endosperm of the maize grain.

1. Both A and R are true and R is the correct explanation of A.
2. Both A and R are true but R is not the correct explanation of A.
3. A is true but R is false.
4. A is false but R is true.

Answer

Both A and R are true and R is the correct explanation of A.

Reason — A is true as the single cotyledon in a maize grain is called the scutellum and it does not store food material for the developing embryo.
R is true and explains A because the food material for the developing embryo in maize is stored in the endosperm, not in the scutellum.

Therefore, Both A and R are true and R is the correct explanation of A is the correct option.

Assertion (A): Epicotyl of the embryonic axis elongates faster in hypogeal germination.

Reason (R): Epicotyl of the embryonic axis elongates faster in epigeal germination and the cotyledons remain underground.

1. Both A and R are true and R is the correct explanation of A.
2. Both A and R are true but R is not the correct explanation of A.
3. A is true but R is false.
4. A is false but R is true.

Answer

A is true but R is false.

Reason — A is True because in hypogeal germination, the epicotyl elongates faster, causing the plumule to emerge while cotyledons stay underground.
R is False because in epigeal germination, it is the hypocotyl that elongates, not the epicotyl, lifting the cotyledons above the soil.

Therefore, A is true but R is false. is the correct option.

Vinita has gone to her grandparents' home situated in a'coastal village'. While visiting, she noticed that several fruits have fallen on the muddy shore. Unlike the seeds she had seen in other plants, these fruits already had long, green shoots emerging from them. Vinita observed that the already-sprouted seedlings easily anchored themselves in the soft mud, preventing them from being washed away by the tides.

(a) Mention the special mode of seed germination seen by Vinita in some plants of the coastal area.

(b) What specific term is used to describe such plants in which the seed germinates inside the fruit itself?

(c) Give two examples of the plants described above in (b).

(d) Which part of the embryo appears much elongated during the above mentioned germination in (a) ?

(e) How are these seeds adversely affected if they fall directly onto the marshy land ?

Answer

(a) The special mode of germination seen is vivipary.

(b) Plants in which the seed germinates inside the fruit itself are called viviparous plants.

(c) Two examples of the plants described above are Rhizophora and Sonneratia.

(d) The part of the embryo that becomes elongated is the hypocotyl.

(e) If these seeds fall directly onto marshy land before developing sufficiently, they may not get enough oxygen, may decay or may be washed away by tides before proper anchorage.