ICSE Class 9 Biology Solutions Chapter 6 Seeds – Structure and Germination

Class 9th ICSE Biology Solutions Chapter 6 Seeds – Structure and Germination

Progress Check

Question 1.
Mention whether the following statements are True (T) or False (F) :
(i) Plumule is the future root and radicle the future shoot of the plant. T/F
(ii) Micropyle serves for the emergence of the radicle.T/F
(iii) Cotyledons in castor, are a big store of food for the embryo. T/F
(iv) Maize grain has a large endosperm. T/F
(v) Tegmen is the outermost coat in bean-seed. T/F
Answer:
(i) F
(ii) F
(iii) T
(iv) T
(v) F

Progress Check

Question 1.
Fill up the blanks by choosing the correct alternative
(i) In a dry seed, the embryo is in ……………… state ……………..
(active/quiescent)
(ii) Water is absorbed by the seed mainly through ……………….
(entire surface/micropyle)
(iii) Very low temperature …………………. the growth of embryo
(inhibits/destroys).
(iv) Germination in pea is ……………….. (epigeal/hypogeal)
(v) Coleoptile is a part found in the germinating ………………
(castor/maize)
(vi) Alkaline pyrogallic acid is used for absorbing ………………. during experiments on germination.
(oxygen/carbon dioxide)
Answer:
(i) quiescent
(ii) entire surface
(iii) inhibits
(iv) hypogeal
(v) maize
(vi) oxygen.

Review Questions

A. Multiple Choice Type :

Question 1.
Which one of the following plant parts is correctly matched with one of its stated characteristics?
(a) Mango seed …………….. aleurone layer
(b) Bean seed ……………… endosperm
(c) Maize grain ……………….. coleoptile
(d) wheat grain ………………… exalbùminuous
Answer:
(c) Maize grain ………………. coleoptile

Question 2.
Seeds sown very deep in the soil fail to germinate because,
(a) cannot exert enough force to push the soil upward
(b) do not get enough sunlight
(c) get too much water
(d) do not get enough oxygen
Answer:
(d) do not get enough oxygen

B. Very Short Answer Type :

Question 1.
Are the following statements true (T) or false (F)? Give reason in each case.
(i) Some seeds have no cotyledons at all; (False)
Reason -Monocotyledonous seeds contain one cotyledon and dicotyledonous seeds contain two cotyledons.

(ii) Maize grain is a fruit and not a seed. (False)
Reason – The maize grain is actually a fruit in which the fruit wall and the seed-coat are fused together

(iii) Seeds fallen in a flower-bed from the previous crop usually do not germinate until the next sowing season. (True)
Reason – The seeds are dry and in dormant state. The germination take place only when the, seed is traffic sported to favorable environment.

(iv) Oxygen is necessary for the germination of seeds. (True)
Reason – There is much need of energy for the growth, division and respiration of cell which is available only with oxygen
Answer:
(i) F
(ii) F
(iii) T
(iv) T

Question 2.
Name the following :
(i) A monocotyledonous endospermic seed.
(ii) A chemical used in experiments, which absorbs oxygen.
(iii) Part of the plumule above the embryonic axis of the seed.
(iv) A plant which shows viviparous germination.
(v) The layer of endosperm of maize, rich in protein.
(vi) A seed with folded plumule leaves.
Answer:
(i) Maize,
(ii) Pyrogallic acid,
(iii) Shoot,
(iv) Rhizophora,
(v) Aleurone layer,
(vi) Bean.

Question 3.
Fill in the blanks :
(i) In bean seeds, …………….. grows faster and the seeds are brought …………….. ground.
(ii) ………….. is a protective layer of radicle and …………….. protects the rolled plumule.
(iii) A seed is protected by ……………. and ……………..
(iv) Seeds absorb water through ……………. which also helps in diffusion of respiratory gases.
(v) Rice, wheat, and maize are rich in ………………. food.
Answer:
(i) plumule, above,
(ii) coleorhiza, coleoptile,
(iii) seed coat, testa,
(iv) Micropyle,
(v) starch.

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) Radicle grows downward, seed coat bursts, hypocotyl elongates, hypocotyl forms loop above the soil, epicotyl elongates.

C. Short Answer Type

Question 1.
What is the difference between an embryo and a seed?
Answer:
A seed is a mature ovule after fertilization. It contains a tiny living-plant called embryo. The embryo within the seed remains in an inactive or dormant state, until it is exposed to favourable conditions when it germinates.

Question 2.
Give any two examples each of endospermic (albuminous) seeds, and non-endospermic (exalbuminous) seeds.
Answer:
Endospermic seeds e.g., :
Castor, Maize, Poppy. Non-Endospermic seeds e.g., : Bean, Gram, Pea.

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 absorbs food from the endosperm and hence, making it nutritive as 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:
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 call such fruits as grains.

D. Long Answer Type

Question 1.
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 –
It protects the delicate inner parts of the seed from injury and from the attack of bacteria, fungi and insects.

(b) Micropyle –
During germination micropyle allows the water enters the seed through his pore.

(c) Cotyledons –
Contain food for the embryo.

(d) Radicle –
Forms the root.

(e) Plumule – Forms the shoot.

Question 2.
Suggest an experiment to prove that a suitable temperature is necessary for germination.
Answer:

Take two beakers and name them A and B. Place some gram seeds on wet cotton wool- in each of the two beakers. Keep beaker A in an ordinary room and beaker B in a refrigerator. In a day or two, seeds in beaker A will germinate
showing the importance of a suitable temperature for germination. Seeds in beaker B may not show signs, for germination or may germinate after several days though not to the extent the seeds in beaker A germinate.

Question 3.
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:
We call it germination because all the changes leading to the formation of a seedling are collectively called germination. During germination either epicotyl or hypocotyl elongates.

Question 4.
Give two differences in each of the following pairs :
(a) Epigeal germination and hypogeal germination.
(b) Coleorhiza and coleoptile.
(c) Bean seed and maize grain.
Answer:
(a) Epigeal Germination

1. Cotyledons pushed above ground.
2. Hypocotyl elongates.

Hypogeal Germination

1. Cotyledons remain underground.
2. Epicotyl elongates.

(b) Coleorhiza

1. Protective sheath of radicle.
2. Presents towards the pointed end of embryonic region.

Coleoptile

1. Protective sheath of plumule.
2. Presents towards the upper broader side of the embryonic region.

(c) Bean seed

1. Two cotyledons.
2. No endosperm.

Maize grain

1. One cotyledon.
2. Large endosperm present.

Question 5.
Differentiate between germination and vivipary.
Answer:
Germination :
When the embryo in the seed becomes activated and begins to grow into a new plant then it is known as germination.
Vivipary :
It is known as the germination of seed within the fruit while it is still attached to the parent plant.

Question 6.
Justify the statement that the maize grain is a ‘one seeded fruit’.
Answer:
Maize is ‘one seeded fruit’ called caryopsis or grain because pericarp (fruit wall) is fused with testa (seed-coat) to form a protective layer after fertilisation.

Question 7.
What is the role played by the hypocotyl in epigeal germination?
Answer:
In epigeal germination, the cotyledons are pushed above the ground due to rapid elongation of hypocotyl i.e. the region just below the cotyledons.

Working of Hypocotyl in Epigeal germination in Endospermic Seed: Castor Seed

• As the seed absorbs moisture, they swell up. The seed coat bursts and the radicle comes out and grows downwards.
• The radicle elongates and forms the primary root and hypocotyl is visible.
• Hypocotyl elongates and arches above the ground. The two- cotyledons that have been absorbing the surrounding endosperm are still with the ruptured seed coat.
• Hypocotyl elongates further and lifts the seed out of the ground. The seed coat remains below the ground. The food stored in endosperm gradually moves to the growing parts of the embryo and so endosperm also gets thinner and soon it drops.
• Hypocotyl straightens up, and the two cotyledons expand and turns gren in colour. The minute plumule hidden between the two cotyledons now begins to grow. In the ground the primary root produces many secondary roots.

Question 8.
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 the structure named above.
Answer:
(a) The micropyle in the seed coat allows water to enter the seed and thereby helps in germination. Micropyle also allows gases to diffuse in and out through it.
(b) Hypocotyl
(c) Below the seed-coat, there are two thick cotyledons which contain food for the embryo and provide nutrition and protect it.
(d)

Additional Questions

Question 1.
Define the following terms :
(a) Germination
(b) Dormancy
(c) Seedling
Answer:
(a) GERMINATION. “Growing of new plant from a seed under suitable conditions like water, oxygen and temperature is called GERMINATION.”
OR
“The sum total of all the processes by which the dormant embryo of the seed grows out of the seed coats and establishes itself as an independent seedling is called GERMI¬NATION.”

(b) DORMANCY.
“The phenomenon in which a seed does not germinate even when provided with all the suitable conditions necessary for germination is called DORMANCY” and seed is called DORMANT SEED.

(c) SEEDLING.
“Is a stage in the growth of a plant before it has become wholly independent of the food stored in it.”

Question 2.
State two points of difference between epigeal germination and hypogeal germination.
Answer:
Epigeal Germination Hypogeal Germination

Question 3.
With the help of neatly labelled sketches, briefly outline the stages in the germination of a bean seed.
Answer:
Stages in Germination of a bean seed are :
1. Under favourable conditions the seed imbibes large quantities of water and swells up. As shown in Fig. (1) bewow

2. The seed coat ruptures at the radicular end. in fig (2)


GERMINATION OF BEAN SEED

3. The radicle pierces out of the seed coat, bends downwards and grows into the soil. Show in fig. (3)

4. The radicle forms the primary root. Lateral roots begin to emerge. Root hairs appear in the region where elongation has ceased. Water and salts absorbed by the root hairs are passed onto the seedling. Meanwhile the hypocotyl elongates and arches upwards above the soil. The two cotyledons are within the ruptured seed coat. Shown in fig. (4)

5. The hypocotyl straightens, pulling the cotyledons into the air. The ruptured seed coats may remain below the soil or are shed above the soil. Shown in fig. (5)

6. The hypocotyl becomes completely erect. The two cotyledons diverge to form the flat, green cotyledonary leaves. The epicotyl elongates, bearing at its tip the plumule. Shown in fig. (6).

7. Young leaves unfold at the tip of the epicotyl. The cotyle¬dons shrivel up and are shed. The primary root gives branches and persists all through the life of the plant. Such a root is called a tap root. The young leaves now prepare food. As shown in Fig. (7).

Question 4.
Give one examples each of :
(i) Dicotyledonous non-endospermic seeds showing hypogeal germination.
(ii) Monocotyledonous endospermic seeds showing hypogeal germ nation.
Answer:
(i) Pea, gram
(ii) Rice, maize

Question 5.
State the effect of the following on the growth of a seedling :
(i) Weak sunlight
(ii) Lack of magnesium
(iii) Force of gravity
Answer:
(i) Effect of weak sunlight
on growth of a seedling. Plants grow with weak, soft arid slender stems and branches with elongated internodes, pale green or yellow in colour and seldom produce flowers and fruits. Roots are also poorly developed and are called ETIOLATED plants.

(ii) Lack of magnesium.
As magnesium is essential for synthesisation of chlorophyll. Such seedlings lack chlorophyll.

(iii) Force of gravity.
Determines the direction of growth of particular organs of the plant body. Roots grow towards gravity, and the stem away from it.

Question 6.
(i) What is meant by tropism?
(ii) Fill in the blanks with the appropriate terms :
(a) The root is positively ……………….
(b) The root is …………….. hydrotropic.
(c) The root is negatively …………….
(d) the stem is negatively ……………………
(e) The stem is ……………. hydrotropic.
(f) the stem is positively ………………..
Answer:
(i) Tropism. “The movement of a plant in the direction of stimulus is called (TROPISM).

(ii) (a) GEOTROPIC. It grows toward the soil.
(b) Positively.
It grows towards water.
(c) Phototropic.
It grows away from sunlight.
(d) Geotropic.
It grows from the soil.
(e) Negatively.
It grows away from water.
(f) Phototropic.
It grows towards sunlight.

Question 7.
Explain the term ‘irritability’ with respect to plants.
Answer:
Plants being living being show response to Stimuli i.e. shows movement to heat, light, electricity, gravity, certain chemicals etc.

Hence.
IRRITABILITY is the capacity of plants or their particular organs to receive stimuli from without and to respond to them is called IRRITABILITY.
Irritability expresses itself in some kind of movement and is decided advantage to the plant since by this movement it can adjust itself according to the conditions of the environment.

Question 8.
What is growth?
Answer:
Growth is the irreversible change in the structure and for development of a cell, tissue, organism.

Question 9.
What is the main difference between growth in plants and growth in animals?
Answer:
The growth in plants is localised in the lateral and Apical meristems and occurs throughout the life of the plant. In animals, all cells are capable of dividing and growth is proportionate and determinate i.e. stops after maturation.

Question 10.
What is meant by development?
Answer:
All the cells of body do not divide at the same rate. As a result our body slowly changes shape. This is called DEVELOPMENT.

Question 11.
Name the parts from which the following develop after fertilisation in a flower.
(i) Seed
(ii) Stalk
(iii) Embryo
(iv) Endosperm
(v) Seed coats.
Answer:
(i) Ovule
(ii) funicle
(iii) Egg-cell
(iv) Definitive nucleus
(v) Integuments with hilum, micropyle, raphe and chalaza.

Question 12.
(a) A seed may be endospermic or non-endospermic. Explain the underlined terms.
(b) Give two examples of each :
(i) Endospermic seed :
(ii) Non-endospermic seed :
Answer:
(a)

• ENDOSPERMIC – “Seeds containing endosperm which store food are called ENDOSPERMIC SEEDS.”
• Non-ENDOSPERMIC – “Seeds in which endosperm is thin and papery and the cotyledons store food are called Non-ENDOSPERMIC SEEDS.”

(b) (i) Castor, Papaya
(ii) BEAN, PEAS.

Question 13.
In the diagram given below, mark the following parts, and state the function of each :
(i) Testa
(ii) Micropyle
(iii) Hilum
Answer:

(i) Testa :
Is the outer tough layer. It protects the seed from fungi, bacteria and insects.

(ii) Micropyle :
A minute pore above the hilum which allows entry of water into the embryo.

(iii) Hilum :
Is Scar left by the stalk and it represents the point of attachment of the ovule to the ovary wall.

Question 14.
Name the parts of the embryo and state the function of each.
Answer:
(i) Cotyledons :
In endospermic seeds cotyledons are fleshy and full of food. In non-endospermic cotyledons are thin and papery. Cotyledons remain attached to the embryonic axis.

(ii) Radicle :
It grows and develops into root system of the plant. It is pointed, lower end of the axis.
(iii) Plumule :
The feathery or leafy end of the axis is called the plumule. It grows into the shoot system of the plant.

Question 15.
On the diagram given below, label the parts of the embryonic axis.
Answer:

Question 16.
(a) What is meant by germination?
(b) Explain the significance of the following factors in seed germination :
(i) Water
(ii) Oxygen
(iii) Temperature
(c) Explain why seeds planted deep in the soil fail to germi¬nate.
Answer:
(a) The process of growing a seed into seedling (plant) is called germination.

(b) (i) dissolves the salts and enzymes present in cotyledons. It softens the seed coat. Seed coat swell up and burst open and helps embryo to come out.

(ii) is necessary for seed, for protoplasm to divide and grow during germination large amount of energy needed is provided by oxygen. Oxidation of stored food produces energy.

(iii) A suitable temperature is needed for germination of seed. Tropical plants have this temperature 25°- 40°C while Temperate Plants have optimum temperature 10°C to 20°C.

(c) Seeds planted deep in the soil fail to germinate, since they do not receive a proper supply of oxygen.

Question 17.
What is meant by dormancy?
Answer:
Is the period after maturation during which a seed will not germinate even when provided with all the conditions necessary for germination.

Question 18.
What is a seedling?
Answer:
Is a stage in the growth of a plant before it has become wholly independent of the food stored in it.

Question 19.
Give two examples each of seeds that store the following reserve food :
(i) Starch :
(ii) Oils :
(iii) Proteins :
Answer:
(i) Wheat : maize, rice
(ii) Mustard : Sunflower
(iii) Pulses : grams, peas.

Question 20.
A beaker containing distilled water was set up with three beans as shown below :

(i) State what you would observe after a few days?
(ii) Explain your observation with réspect to each seed.
(a) Seed A:
(b) Seed B:
(c) Seed C:
Answer:
(i) A – receives oxygen but no water, does not grow.
B – receives both oxygen and water and germinates properly.
C – receives water and barety enough oxygen. Hence it begins to germinate but soon stops.

(ii) (a) Does not germinate
(b) Germinates properly
(c) Starts germinating but soon stops.

Question 21.
(a) Name the two main types of germination.
(b) Give two points of difference between the types of germination named in (a).
(c) Give two examples of each type of germination named in (a).
Answer:
(a

1. Epigeal germination
2. Hypogeal germination

(b)

1. In Epigeal germination – Hypocotyl elongates, Cotyledons become green leaves.
2. In Hypogeal germination – epicotyl elongates, Cotyledon remain below the soil.

(c)

1. Epigeal germination – Bean, Cotton
2. Hypogeal germination – Pea, rice.

Question 22.
Shown below are the stages in seed germination of a certain type :
(i) Identify the type of germination taking place.
(ii) Label the parts indicated with guidelines.
(iii) State the development taking place in each stage numbered 1 to 7.

Answer:
(i) Epigeal germination.

1. Seed imbibes large quantities of water and swells up. Under favourable conditions.
2. The seed coat ruptures at the radicular end.
3. The radicle pierces out of the seed coat, bends downwards and grows into the soil.
4. The radicle forms the primary root. Root hairs appear, Hy- pocotyl elongates and arches upwards above the soil. Two cotyledons are within the ruptured seed coat.
5. The hypocotyl straightens, pulling the cotyledons into the air. The ruptured seed coats may rertiain below the soil or shed above the soil.
6. The hypocotyl becomes completely erect. The two cotyledons diverge to form the flat, green cotyledonary leaves the epicotyl elongates, bearing at its tip the plumule.
7. Young leaves unfold at the tip of the epicotyl. The cotyledons shrivel up and are shed. The primary roots give branches. This is called Tap root. The young leaves now prepare food.
   

Question 23.
Shown below are the stages in the germination of a certain type :
(i) Identify the type of germination taking place.
(ii) Label the parts indicated with guidelines.
(iii) State the development taking place in each stage numbered 1 to 5.

Answer:
(i) Hypogeal germination

1. Seed absorbs water and swells. The cotyledons absorb food material stored in the endosperm.
2. The radicle pierces through the protective root sheath and grows downwards into the soil.
3. The coleoptile elongates and pierces out of grain opposite in direction to the coleorhiza. The radicle develops into root.
4. A cluster of fibrous roots arise around the base of the pri¬mary root. The first leaf of the plumule pierces out of the coleoptile.
5. More leaves appear in succession. Primary root perishes giving rise to a fibrous root system.

Question 24.
Mention five conditions that are necessary for growth.
Answer:

1. Supply of water
2. Supply of oxygen
3. Light
4. Suitable Temperature
5. Supply of Nutrients.

Question 25.
(a) State the characteristics of a plant grown in the ab¬sence of light for a long period.
(b) Give a term that describes the conditions stated in (a).
Answer:
(a) Though in the initial stage of growth light not absolutely needed but continued absence of light affects the growth. Weak, soft, slender stems and branches with elongated internodes pale green (or yellow, in colour seldom produce flowers and fruits. Roots are also poorly developed.

(b) The condition is called ETIOLATED.

Question 26.
What is a plant growth hormone?
Answer:
AUXIN is an organic substance which is produced within a plant and which at low concentrations influences the growth process, usually at a site other than its place of origin.

Question 27.
What is the effect of gravity on plant growth?
Answer:
It determines the direction of growth of particular organs of the plant body. Roots grow towards gravity and stem away from it.

Question 28.
Explain the following terms :
(i) Tropism
(ii) Irritability
(iii) Chemotropism
Answer:
(i) The movement of plant in the direction of stimulus is called TROPISM.
(ii) The capacity of plants or their particular organs to receive stimuli from without and to respond to them is called IRRITABILITY.
(iii) “Movement of plant part due to chemical stimulus is called CHEMOTROPISM” Example-pollen tube growth.

ICSE Class 9 Biology Solutions