Asexual Reproduction in Plants

THE TEACHERS’ GUIDE

SUBJECT : BIOLOGY

TOPIC : REPRODUCTION IN PLANTS

SUBTOPIC : Asexual Reproduction in Plants

CLASS : Senior Four

CLASS SIZE : 60 students

TIME REQUIRED : Minimum: 120 minutes – 160 minutes (i.e. 3 - 4 periods)

Brief description of unit

Plants give rise to young ones of their kind. This is either by seeds or vegetative part of the plant. The vegetative part may be a root, stem or leaf.

In this Unit learners will learn about vegetative reproduction as a form of asexual reproduction. They will also appreciate the fact that new off springs can be produced both naturally and artificially without involving the fusion of gametes.

Content and outline

• Concept of vegetative reproduction in plants
• Stem tubers and bulbs
• Suckers and rhizomes and their parts
• Corm and its parts
• Differences between corm and rhizome
• Practical activity on drawing, and labelling of vegetative parts
• Artificial propagation; use of stem cuttings, budding, layering, grafting, marcotting
• Importance of artificial propagation in plant growth

Objectives

• Define vegetative reproduction
• List plant parts used in vegetative reproduction
• Explain vegetative reproduction using leaves of Bryophyllum
• Describe structure of stem tuber and bulb
• Draw and label parts of sucker and rhizome
• Describe parts of a corm
• List differences between a rhizome and a corm
• Draw and label vegetative reproductive organs
• Explain how stem cuttings are used to produce new plants
• Describe the procedure used in marcotting, layering, grafting, to produce new plants
• Explain the importance of artificial propagation with regard to crop production and profitability

Requirements or Materials

• Runner stems
• Suckers
• Bulbs
• Rhizomes
• Bryophyllum leaves having developing buds.
• Charts showing one or all the vegetative reproductive structures.
• Video showing the procedure for grafting, layering, marcotting or budding
• Animated video or story about the process of vegetative reproduction namely layering, marcotting.
• Charts showing the process of artificial propagation using marcotting, layering, cuttings, budding, grafting.
• Resource person to talk to learners about artificial vegetative reproductive means.

Job related life skills

By the end of this topic, learners are expected to have acquired the following Job related Skills:

1. Personal attributes – self confidence, time management, creativity/imaginative, recording skills, enthusiasm, imagination, leadership skills and self awareness.

2. Communication – observation & listening skills, recording, reading, reporting in writing.

3. Team work – task-oriented leadership skills, group work.

4. Problem solving - information seeking, Practical experiment, environmental protection & conservation, seeking for information (research), discussion.

5. Application of number - numeracy (as they compare crop yields in treated and untreated plots)

Learners’ activities

Activity One – Fieldwork activity.

Structure of vegetative reproductive organs

Let learners move out to the field and Study the structure of the vegetative reproductive organs using actual specimens of their own. E.g. bulbs, suckers, Bryophyllum leaves, root tubers and stem tubers.

Procedure:

Studying structures of different vegetative reproductive organs

• Guide learners to recognize and identify the different, reproductive organs, Bryophyllum leaf, ginger potato tuber, stem tubers.
• Asks learners to identify parts of the different vegetative organs.

Activity Two

Let learners observe, draw and label the different organs of perennation.

Procedure:

• Guide learners to identify the parts of the vegetative reproductive organs.
• Demonstrate to them how to draw the vegetative reproductive organs.

Activity Three

Ask learners to list the differences between the different vegetative reproductive parts/organs namely, corms and rhizomes, suckers and bulbs, etc.

Procedure:

Brainstorm and lead the discussion to generate the differences between the various vegetative reproductive organs.

Activity Four

Demonstrate to the learners how artificial propagation procedures like layering, marcotting, budding, use of cuttings, grafting are carried out, and the use of perennating organs e.g. corms, rhizomes, bulbs, tubers, etc. .

Procedure:

• Invite a resource person to demonstrate to learners and also make a presentation about the procedures of artificial reproduction mechanisms like grafting, marcotting, layering, etc.
• Give learners chance to ask him/her questions and to interact freely with this resource person.

Activity 5

Field activity

1. Visiting a tree seed nursery centre like Namanve, to observe how grafting and other artificial propagation procedures are carried out.
2. Visiting an agricultural research centre like Kawanda Agriculture Research Institute (KARI), Namalele Agriculture Research institute e.t.c. to see the procedures of artificial propagation.

Procedure:

• Organize learners into groups of 5 to 8
• Ask each of them to carry with him/her a piece of paper and a pen. Emphasise to them to take notes of what they will have observed from the demonstrations of grafting, layering, etc while at the research centre.
• Ask the facilitator (resource person) about the different artificial propagation methods and their importance.
• Let learners report their findings to their colleagues when they get back to class so as to share results as a class.

Learners’ Exercise

Objective questions

1. The part of the Irish potato plant responsible for vegetative reproduction is:

A. Root

B. Stem

C. Leaf

D. Fruit

2. What feature of a shoot enables it to be used as an organ of vegetative reproduction?
   1. Leaves
   2. Flowers
   3. Lateral buds
   4. Lateral roots

3. Which of these does not represent artificial vegetative reproduction?

A. Cuttings

B. Layering

C. Grafting

D. Sporulation

2. Which of the following structures does the diagram below represent?

A. Corm

B. Stem tuber

C. Rhizome

D. Sucker

5. Which of the following is an example of a plant in which a leaf gives rise to new plants?

A. Cocoyam

2. Onion
3. Bryophyllum
4. Ginger

6. Which of the following is NOT a disadvantage of natural vegetative reproduction?

A. Successive generations become weaker.

B. Plants grow close to each other and so become overcrowded.

C. Diseases of parent plants may spread to young ones.

D. Bearing of identical offspring

7. The structure onto which a shoot or bud is attached in artificial propagation is called........

1. Scion
2. Stock
3. Bulbil
4. Bud

8. The feature on the diagram that is responsible for vegetative reproduction is

labelled (the leaf is not labelled)

A F

B G

C H

D I

Short answer question

9(a) What is vegetative reproduction?

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………………………………………………………………………………………

(b) State two examples of plants, which can be grown using artificial vegetative propagation

………………………………………………………………………………………

………………………………………………………………………………………

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(c) Give 3 advantages of vegetative reproduction to plants.

………………………………………………………………………………………

………………………………………………………………………………………

………………………………………………………………………………………

Essay question

10 a) What are the advantages and disadvantages of vegetative reproduction?

b) Which artificial method of propagation would you use for each of the

following?

Sugarcane, Oranges and Bougainvillea

c) Describe how marcotting is done.

Answers

1 B 2. C 3. D 4. C

5. C 6 D 7. B 8. A

9 (a) Vegetative reproduction is a type of reproduction where a vegetative part of a plant gives rise to new plants.

(b) Mango, avocado, tangerine, orange

• It gives rise to identical offsprings
• Offsprings bear good qualities of the parent plant.
• The process does not need pollination and fertilization.

10. a) Advantages

• New plants are identical to parent plant.
• Offsprings have good qualities of parent plant.
• Easy process of reproduction requiring no pollution and fertilization.
• Enables plants without viable seeds like bananas to reproduce.

Disadvantages

• No variation among offsprings.
• No genetic vigour.
• Unstable conditions may destroy the entire population.
• Produces fewer plants compared to reproduction by seeds.

b) Sugarcane - use of cuttings

Oranges - Grafting and budding

Bougainvillea - Layering or marcotting, use of cutting

3. Marcotting involves the ringing of the stem.

Mulch or manure is then applied to the ringed area. Secure the mulch or manure on to the stem using banana fibres or polythene.

The ringed area produces roots, or rooting occurs at the area where manure or mulch has been applied.

The twig with roots is cut off from the parent plant and planted to obtain a new plant.

Glossary

1. A bulb is a modified underground shoot with a short flattened stem and fleshy leaf bases e.g. onion. .

Rhizome: is a horizontal underground stem swollen with food. It has scale leaves that enable a plant to survive from one growing season to the next. In some species, it is used to propagate the plant vegetatively e.g. ginger.

Grafting: (Of plant tissues) is a horticultural practice used to propagate plants especially certain shrubs and fruit trees artificially.

Scion: This is a bud or shoot of the desired plant that is grafted onto a rootstock.

Budding: (in horticulture) is a method of grafting in which a bud or a scion is inserted onto the stock usually beneath the bark.

Corm - Is an underground plant organ formed by certain plants like crocus that enables them to survive from one growing season to the next. It consists of a short swollen vertical stem surrounded by protective scale leaves.

Vegetative reproduction: A form of asexual reproduction in plants whereby new plants develop from specialized vegetative structures like roots, stems or leaves that become detached from a parent plant.

Sucker is a short stem that arises from the underground root or stem and grows at the expense of the parent plant.