Vegetative Propagation - Agriculture Form 2
Vegetative propagation methods
Suggested Practical Activities in vegetative propagation
Activity 1:Grafting practical
1a)Learners should carry out the whip(tongue)grafting method using suitable plants for example lemon (root stalk) & orange (scion)
i.Ensure the scion and rootstock are of the same diameter
ii. Make a smooth cutting that is slanting on both scion and the rootstock ,using a sharp knife.
iii. Bring the cut surface together and firmly hold the union together by wrapping it with a grafting tape, or polythene paper.
iv. Place the graft under a shade and water regularly.
Note the graft union is successful when the scion buds starts growing into shoots
Vegetative propagation is an important method of raising crops in the nursery and seedbed. It is important to be familiar with the following terms used in Vegetative propagation:-
- Grafting: It is the practice of uniting of two separate woody stems for continued growth as one plant.
- Scion: Refers to the upper part of the that scion develops into the future plant. It is obtained from another plant.
- Rootstock: The lower part with the rooting system.
- Graft union: The point where plant parts are joined.
- Compatibility: is the ability of the rootstock and the scion to form a successful union.
Root stock- the part with the rooting system in budding and grafting.
Scion- refers to the upper part of the that scion develops into the future plant. It is obtained from another plant.
Compatibility- is the ability of the rootstock and the scion to form a successful union.
Budding- Budding is a technique of propagation where a vegetative bud removed with a bark (scion) is united with another plant ( rootstock ).
Grafting- it is the practice of uniting of two separate woody stems for continued growth as one plant.
Graft union- the point where plant parts are joined.
Layering- is the method of propagation that induces a plant stem to produce roots while still attached to the mother/parent plant.The newly rooted layered stem is then detached and established as new independent plant
By the end of the sub-topic, you should be able to;
- graft a seedling.
- explain the importance of budding, grafting, layering, and tissue culture.
- describe the damage caused by animals on tree seedlings and how to prevent it.
In this lesson we will discuss the various methods of vegetative propagation, these methods are; Grafting, budding layering and tissue culture propagation.
We will also discuss their importance in crop production.
See the video below to appreciate vegetative propagation
Advantages of grafting
- Can be use to produce planting materials through asexual means.
- It makes plants to benefit from good quality rootstocks.
- Can be used to repair damaged plants thus restoring them back to productivity.
- Hastens the growth of seedlings from the graft.
Conditions necessary for successful grafting.
- Only plants that are botanically closely related are compatible e.g Lemon and orange.
- The cambium tissue of the rootstock must be in contact with that of the scion.
- The graft union must be covered with grafting wax to prevent rotting.
Methods of grafting
Whip / tongue grafting
Used when the diameter of the two plants are of the same size. (pencil thick) A slanting cut is made using a sharp sterilised knife on the scion and the rootstock. The two are then fitted and tied together using grafting tape. It is the commonest method of grafting and tends to be more successful than the other methods.
The method is practiced when the rootstock is of a larger diameter than scion.The scion is inserted onto a cut made on the side of the rootstock.
- This method requires good cambial contact to be successful.
- A V- shaped split is the middle of the rootstock using a grafting knife
- The scion is inserted in the split ensuring that the cambial tissue is in proper contact.
- The graft union is method is tied together using a grafting tape.
See the video below to appreciate method of grafting
Budding is a technique of propagation where a vegetative bud removed with a bark (scion) is united with another plant ( rootstock ).
Common methods budding are:
- Patch budding.
The rootstock and the scion should have the desired characteristics.
The bud is inserted onto a slit made on bark of the rootstock and the union held tightly using a budding tape.
The bark is then raised slightly and the vegetative bud inserted and pushed downwards until it is below the horizontal line of the rootstock.
The bud union is then tied firmly using a budding tape.
The budding tape is removed two weeks after grafting to inspect the buds.
The rootstock is then cut a few centimetres above the union, the green bud develops into a shoot.
When the shoot is 25 cm it is tied onto the rootstock to prevent it from strong winds
If the bud is green then bud union is successful.
If the bud is dry the bud union is unsuccessful and must be repeated.
It involves inserting on various different desired locations on the same stem of young trees.
It allows production of different varieties of fruits and flowers on the same plant as long as they are from the same species.
It involves the removal of a rectangular patch of bark from the rootstock and replacing with another patch with the desired bud stick of the same dimensions and shape. The union is then tied both at the top and the bottom so as to hold tightly.
Importance of budding and grafting
Plants with desirable root characteristics may be utilised to produce plant products.
- The top part of the tree can be changed from being undesirable to desirable.
- More than one type of fruits or flowers can be produced on the same plant.
- Can be used to repair old and damaged trees.
- Can be used to propagate trees that cannot be propagated in other way.
- Can be used to shorten maturity age of trees.
Layering is the method of propagation that induces a plant stem to produce roots while still attached to the mother/parent plant.
Newly rooted layered stem is then detached and established as new independent plant.
Common types of Layering includeAerial layering / Marcotting:
It is used on hardwood where the stem cannot be bent easily to reach the ground.The moist rooting media is heaped and tied around the stem, induces root development.
A shoot of currently growing bearing a terminal branch is bent to the ground and covered with a layer of wet soil, the terminal end is left uncovered.
Rooting can be initiated by cutting the bark at the covered part.
The branch to be propagated is laid in a shallow trench, held in position by pegs and covered with moist soil.Buds and roots develop at various points. The shoots are then cut and transplanted as independent plants
The branch should be long and flexible; the branch is bent several times along its length and held in position by pegs.Several new rooted plants are produced which are transplanted as independent plants.
It involves cutting the stem of a plant to the ground during the dormant season, then covered with soil.New shoots with roots develop and can split from the mother plant and established independently.
Tissue Culture Propagation
Tissue culture propagation is a biotechnology method of propagation in which a part of plant or single plant cell is isolated properly under controlled laboratory conditions and placed in suitable growth medium where it will develop into a whole plant.
Propagules or explants, derived from shoot tips where cell are undifferentiated.
Culture medium containing correct nutrients and growth regulator, under the correct environmental conditions eg light intensity, relative humidity, temperature.
Importance of Tissue culture propagation
- Can be used to recover and produce pathogen free plants eg control of viral diseases.
- Mass production of propagules especially from one superior plant.
- It is a cheap and faster method of propagation and requires a very small space.
See the video below to appreciate tissue culture propagation
Stages of tissue culture propagation
Establishment of an aseptic media using ingredients such as inorganic minerals, minerals, carbon and energy source (sugar), vitamins, growth regulators, organic supplements.
Developing the propagule through enhancing cell division and enlargement.
Use of disinfectants to eliminate contaminations, eg alcohol, mercury chloride, calcium or sodium hypochlorite and antibiotics.
A series of sub culturing to encourage rapid multiplication of propagules through somatic development of embryos to produce auxiliary buds and adventitious roots.
Culture medium to be enriched with substances that enhance development of plant organs.
This stage involves preparation of propagule for establishment.
Rooting of regenerated plantlets. This is through adding auxins to the growth medium
Hardening of plantlets to tolerate moisture stress and attack by pathogens. This may involve change in physical environments of the plantlets.
Converting the plantlets from heterotrophic to autotrophic mode nutrition.
Crop Production III (Nursery Practices)
Transplanting tree seedlings
The are raised in potted sleeves, bags or seedling boxes. They take much longer in the nursery bed, the time varying depending on the particular species
Hole are dug one month before transplanting of the seedlings. The topsoil is separated from the subsoil. Topsoil is used to halfway fill the planting hole.
Seedbed should be well watered a day before transplanting. For easy lifting and for the soil to stick around the roots hence prevent root damage.
Done at the onset of heavy rains. Use appropriate type and amount of fertilizer and manure in the planting hole.
Seedlings are placed at the centre of the hole, and a sharp knife used to cut and remove the polythene sleeves.
Covered at the same depth as was in the nursery. The soil is then firmed gently .
Management of seedlings
The seedling is watered, mulched and shaded.
Protected from domesticated and wild animals when still young.
Different types of fences can be erected around the trees, these include
Protecting trees seedlings after transplanting.
- Use of stakes or timber fence.
- Use of plain wire and stakes fence.
- Chicken wire on stakes fence.
- Barbed wire on stakes fence.
- Thorns and bushes fence.
- Post and Iron sheets fence.
- Post and polyethylene sheets
Protected trees seedlings after transplanting.
As a learners you are required set up a tree nursery in schools or acquire tree seedlings transplant and manage them appropriately.
See the video to appreciate tree seedlings transplanting.
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