BIOLOGY LESSON NOTE ON CROP PROPAGATION

Topic: Crop Propagation

Class: Senior Secondary School 2 (SS2)
Subject: Biology

Specific Objectives

By the end of this lesson, students should be able to:

  1. Define crop propagation.
  2. Differentiate between sexual and asexual propagation.
  3. Identify and explain various methods of crop propagation.
  4. Highlight the advantages and disadvantages of each method.
  5. Recognize common examples of crops propagated using each method.

Lesson Content

1. Meaning of Crop Propagation

Crop propagation refers to the process by which plants reproduce or are reproduced to give rise to new plants. This can occur naturally or be carried out artificially by farmers or agricultural scientists. It is a vital practice in agriculture that ensures the continuous production of food and other plant-based resources.

2. Types of Crop Propagation

Crop propagation is broadly categorized into two main types:

  • Sexual Propagation (Seed Propagation)
  • Asexual Propagation (Vegetative Propagation)

3. Sexual Propagation

This involves the use of seeds to grow new plants. It occurs through the process of fertilization, where male and female gametes fuse to form a zygote that develops into a seed.

Examples: Maize, Rice, Beans, Okra, Tomato.

Advantages:

  • Promotes genetic variation.
  • Seeds are easy to store and transport.
  • Useful for breeding new plant varieties.

Disadvantages:

  • Slower process compared to asexual propagation.
  • Plants may not retain the desirable traits of the parent plant.

4. Asexual (Vegetative) Propagation

This involves the reproduction of new plants without the use of seeds. It makes use of vegetative parts such as stems, roots, and leaves.

Types of Asexual Propagation:

a. Stem Cuttings:

  • Parts of the stem are cut and planted.
  • Example: Cassava, Sugarcane.

b. Grafting:

  • A portion of a stem (scion) is joined to the rooted part (stock) of another plant.
  • Example: Mango, Citrus fruits.

c. Budding:

  • A single bud is inserted into the bark of another plant.
  • Example: Orange, Rose.

d. Layering:

  • A branch is bent to touch the ground, covered with soil, and it forms roots.
  • Example: Guava, Grapes.

e. Suckers:

  • New shoots grow from the root or base of the parent plant.
  • Example: Banana, Plantain.

f. Runners:

  • Horizontal stems grow along the ground and form new plants at nodes.
  • Example: Strawberry.

Advantages:

  • Fast and efficient.
  • Maintains genetic uniformity (clones).
  • Useful in producing plants that do not produce viable seeds.

Disadvantages:

  • Lack of genetic diversity.
  • Some methods are labor-intensive.
  • Risk of transmitting diseases from parent plant.

Evaluation

1. Differentiate between sexual and asexual propagation.
2. Mention two crops propagated by seeds and two by stem cuttings.
3. Explain the process of grafting and its importance.
4. List any three advantages of vegetative propagation.
5. What is the main disadvantage of using asexual propagation in agriculture?

Objective Questions (20)

1. Crop propagation refers to:
A. Animal production
B. Watering of crops
C. Reproduction of plants
D. Weeding of crops
Answer: C

2. Which of these is a method of sexual propagation?
A. Budding
B. Grafting
C. Sowing seeds
D. Layering
Answer: C

3. Asexual propagation does NOT involve:
A. Seed formation
B. Stem cuttings
C. Budding
D. Grafting
Answer: A

4. The fusion of male and female gametes is called:
A. Pollination
B. Germination
C. Fertilization
D. Budding
Answer: C

5. Which plant is commonly propagated by stem cuttings?
A. Maize
B. Cassava
C. Beans
D. Tomato
Answer: B

6. Grafting is a method of:
A. Seed propagation
B. Soil preparation
C. Vegetative propagation
D. Irrigation
Answer: C

7. One advantage of sexual propagation is:
A. Uniform offspring
B. Fast growth
C. Disease resistance
D. Genetic variation
Answer: D

8. A sucker is used to propagate:
A. Mango
B. Plantain
C. Beans
D. Yam
Answer: B

9. Layering involves:
A. Cutting off the stem
B. Bending a branch to the ground
C. Cutting off the root
D. Grafting two plants
Answer: B

10. One disadvantage of asexual propagation is:
A. High cost
B. High genetic variation
C. Risk of disease transmission
D. Long germination time
Answer: C

11. Which of the following crops is not propagated by seed?
A. Rice
B. Maize
C. Potato
D. Beans
Answer: C

12. In grafting, the upper part inserted is called:
A. Rootstock
B. Bud
C. Scion
D. Node
Answer: C

13. The rooted part in grafting is known as:
A. Runner
B. Scion
C. Rootstock
D. Sucker
Answer: C

14. Which propagation method maintains the parent plant's traits?
A. Sexual
B. Natural
C. Asexual
D. Pollination
Answer: C

15. Which of these crops uses runners to propagate?
A. Banana
B. Strawberry
C. Sugarcane
D. Beans
Answer: B

16. A plant that can be propagated by budding is:
A. Okra
B. Orange
C. Maize
D. Millet
Answer: B

17. The main reason for using vegetative propagation is to:
A. Save cost
B. Produce new species
C. Get fast and uniform results
D. Increase seed use
Answer: C

18. Which method is best for propagating plants that do not produce viable seeds?
A. Sexual propagation
B. Germination
C. Asexual propagation
D. Fertilization
Answer: C

19. Cassava can be propagated by:
A. Seeds
B. Grafting
C. Stem cuttings
D. Budding
Answer: C

20. Banana is propagated through:
A. Seed
B. Runners
C. Suckers
D. Tubers
Answer: C

Conclusion

Crop propagation is an essential practice in agriculture, ensuring the continuous supply of food and economic crops. By understanding both sexual and asexual propagation methods, students and farmers can choose appropriate techniques to enhance crop yield, preserve desirable plant traits, and support agricultural sustainability. Whether by seeds or vegetative parts, knowing how plants multiply helps in planning effective cultivation practices.


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