CBSE Class 10 Science Practical Skills – Dicot Seed

CBSE Class 10 Science Practical Skills – Dicot Seed

BASIC BUILDING CONCEPTS
The ovule after fertilisation develops into seed. A scar called hilum is present at the outer surface of seed. This is the point where seed stalk remains attached to seed. A small pore called micropyle is also present near the hilum. Each seed has an outer covering called seed coat. The seed coat encloses an embryo which is differentiated into plumule, radicle and cotyledons. Plumule is the upper terminal part of embryo which elongates and develops into future shoot. The lower end of embryo is radicle. Radicle develops into future root. In a seed, one (in monocots) or two (in dicots) cotyledons may be present. The cotyledons are also known as seed leaves. The part of embryonic axis between the plumule and point of attachment of cotyledons is called epicotyl. Similarly, the part of embryonic axis between the radicle and point of attachment of cotyledons is called hypocotyl.

AIM
To identify the different parts of an embryo of a dicot seed (pea, gram or red kidney bean).

MATERIALS REQUIRED
Seeds of bengal gram/red kidney bean, forceps, cloth, magnifying glass, petridish, water.

THEORY

PROCEDURE

1. Soak a few bean seeds and keep them overnight.
2. Drain the excess water.
3. Cover the seeds with a moist cloth and keep them aside for a day.
4. Peel off the seed coat carefully.
5. Using your thumbs or the forceps, open the bean seed so that it falls into two halves.
6. With the help of the magnifying glass, locate the parts of the bean embryo carefully.
7. Draw a sketch of the inside of the dicot seed that you examined. Label all its parts.
   

OBSERVATIONS

1. Bean seed is kidney-shaped with a concave and convex side.
2. The concave side which is slightly darker has a scar called hilum.
3. Adjacent to hilum a small pore known as micropyle is present.
4. The seed is covered by a seed coat.
5. The embryo consists of two large, white and kidney-shaped cotyledons.
6. The cotyledons are attached laterally to the curved embryonal axis.
7. Rod shaped and slightly bulgy lower end of embryonal axis which lies towards micropylar end is called radicle.
8. Plumule is the upper end of embryonal axis.
9. The part of embryo axis between radicle and attachment of cotyledon leaves is called hypocotyl.
10. The part of embryo axis between plumule and attachment of cotyledon leaves is called epicotyl.

RESULT
The embryo of dicot seeds consists of three main parts – plumule, radicle and two cotyledons.

PRECAUTIONS

1. The cloth which is used to cover seeds should be moist and should not get dry.
2. Seeds should be open carefully so that the embryo does not get damaged.

INTERACTIVE SESSION

Question 1.
What is the difference between a dry seed and the soaked seed?
Answer:
Dry seed has hard and wrinkled seed coat, soaked seed has soft seed coat which can be removed easily.

Question 2.
Why should we soak the seed overnight?
Answer:
Soaking helps the cotyledons to absorb water and the embryo becomes active.

Question 3.
Why should we keep the seed covered with a moist cloth for another day?
Answer:
So that the baby plant grows up a little more.

Question 4.
What is the function of cotyledons?
Answer:
Cotyledons contain food for the baby plant.

Question 5.
What do you understand by dicot seed?
Answer:
A seed which contains two cotyledons.

Question 6.
What is the function of seed coat?
Answer:
Seed coat protects the cotyledons and the embryo during the dormant period.

Question 7.
What would happen if the seed covered with moist cloth is kept in the fridge? Why?
Answer:
If the seeds are kept in the fridge, the temperature required for germination is not available, so the embryo would not be able to grow.

Question 8.
What are the two main parts of the embryo?
Answer:
Plumule which grows into a shoot and the radicle which grows into a root.

Question 9.
What does the radicle grow into?
Answer:
The radicle grows to develop into the root system.

Question 10.
What conditions are required for the seed to grow into a complete plant?
Answer:
The conditions required for the seed to grow into a plant are

• Water
• Oxygen
• Right temperature
• Soil.

PRACTICAL BASED QUESTIONS

Multiple Choice Questions /VSA (1 Mark)

Question 1.
Seeds are produced within
(a) root
(b) stem
(c) fruit
(d) leaf

Question 2.
The development process in which a mature seed develops into a seedling is called
(a) transpiration
(b) germination
(c) photosynthesis
(d) dormancy

Question 3.
The protective covering of a seed is
(a) hilum
(b) stem
(c) seed coat
(d) micropyle

Question 4.
The scar where the seed was attached to the fruit is the
(a) micropyle
(b) hilum
(c) seed coat
(d) stem

Question 5.
Which of the following forms a tiny root?
(a) Radicle
(b) Epicotyl
(c) Hypocotyl
(d) Cotyledon

Question 6.
The baby shoot is formed by the
(a) hilum
(b) radicle
(c) hypocotyl
(d) plumule

Question 7.
Seed coat protects
(a) hypocotyl, hilum
(b) cotyledons, embryo
(c) micropyle, epicotyl
(d) cotyledons, micropyle

Question 8.
Water enters the seed through the
(a) seed coat
(b) hilum
(c) embryo
(d) micropyle

Question 9.
The part of the embryonic axis located above the point of attachment of cotyledons is called
(a) hypocotyl
(b) micropyle
(c) hilum
(d) epicotyl

Question 10.
The part of the embryo between root and cotyledons is called
(a) hypocotyl
(b) epicotyl
(c) plumule
(d) micropyle

Question 11.
The number of cotyledons present in pea, gram, j kidney bean is
(a) one
(b) two
(c) three
(d) either one or two

Question 12.
The food for the baby plant is stored in
(a) seed coat
(b) cotyledons
(c) micropyle
(d) embryo

Question 13.
Embryo consists of
(a) only plumule
(b) only radicle
(c) plumule and radicle both
(d) hilum

Question 14.
After a seed is germinated, it will develop and grow into a young plant. Arrange the following to show the correct order of events taking place during seed germination.
A. root appears
B. seed coat ruptures
C. seedling
D. shoot appears
(a) A, B, D, C
(b) B, A, D, C
(c) B, D, A, C
(d) C, A, B, D

Question 15.
The seed is produced by the fusion of
(a) micropyle and ovum
(b) pollen grains and hypocotyl
(c) pollen grains and ovum
(d) ova and ovum

Question 16.

What is A?
(a) Hilum
(b) Seed coat
(c) Plumule
(d) Micropyle

Question 17.
A student draws the diagram of a dicot seed to show the different parts of its embryo. He has marked its parts as A, B, C and D:

The correct labelling of these parts respectively is
(a) plumule, radicle, cotyledon, seed coat
(b) plumule, radicle, seed coat, cotyledon
(c) radicle, plumule, cotyledon, seed coat
(d) radicle, plumule, seed coat, cotyledon

Question 18.
Following are some differences between dicot and monocot seeds:

Of the above mentioned differences, which are correct?
(a) I and II only
(b) II and III only
(c) I and III only
(d) All I, II and III

ANSWER KEY

1. (c)
2. (b)
3. (c)
4. (b)
5. (a)
6. (d)
7. (b)
8. (d)
9. (d)
10. (a)
11. (b)
12. (b)
13. (c)
14. (b)
15. (c)
16. (c)
17. (b)
18. (a)

Short Answer Questions (2 Marks)

Question 1.
What are the various parts of an embryo of a dicot seed?
Answer:
The embryo is differentiated into three parts— plumule, radicle and cotyledons. Plumule is upper terminal part of embryo which elongates and develops into future shoot. The lower end of embryo is radicle. Radicle develops into future root. Seed leaves are called cotyledons.

Question 2.
What are cotyledons? What is their function in a seed? How is bean seed different from maize seed on the basis of number of cotyledons?
Answer:
Cotyledons are the part of embryo which provide nourishment to developing embryo during germination. Cotyledons contain food for the baby plant. Bean seed has two cotyledons while maize seed has only one cotyledon.

Question 3.
What do you understand by the terms: hypocotyl and epicotyl?
Answer:
The portion of embryonal axis which lies below the cotyledon in a dicot embryo is called hypocotyl. It terminates with radicle.
Epicotyl in the portion of embryonal axis which lies above the cotyledons in a dicot embryo. It terminates with plumule.

Question 4.
Mention the different steps of germination of seed in correct order.
Answer:

1. absorption of water by seeds.
2. rupture of seed coat.
3. emergence of radicle.
4. emergence of plumule.
5. development of radicle into baby root.
6. development qf plumule into shoot.

Question 5.
Differentiate between plumule and radicle.
Answer:

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