PROPAGATION OF CROPS
Propagation is the multiplication of crops population for the continued existence of crop species.
1. Outline the various methods of propagating crops.
2. List the various methods of sowing seeds,
3. State the advantages and disadvantages of each method of propagation.
4. Identify the various organs of vegetative propagation
Propagation is the multiplication of crops population for the continued existence of crop species.
Sexual or seed propagation
This method makes use of seeds. It is common with both self pollinated and cross-pollinated crops. It is sometimes the only possible way to propagate some crops like tomato, maize, rice, pea and groundnut. Seeds can be collected from healthy, vigorous and high yielding plants.
These are sown either directly on the farm or first in nursery before they are transplanted to the farm. Examples of crop that are propagated by seeds are maize, rice, tomato, okra, cocoa, oil palm, rubber, mango, cashew and guava.
Propagation through seeds and fruit
Seed and fruit formation
The main reproductive organ flowering plants is the flower.
The flower consists of two major parts – the male and the female parts.
The stamen is the reproductive organ and it is made up of filaments carrying anthers which contain the pollen grains.
The pistil is the female reproductive organ. It consists of the stigma which receives the pollen grains during pollination; style which connects the stigma to the ovary through which the pollen tube grows during the process of fertilizers: and the ovary which contains the ovules which develop Into seeds.
Classification of fruits for propagation
Fruits may be classified as simple, foot pound, and aggregate.
Simple fruits are those formed from a flower with a monocarpous pistil. Examples are beans, lemon and mango.
Compound/multiple fruits are formed from an inflorescence or bunch whose fruit-lets are fused together to form a , jingle large fruits. Examples are pineapple and jack fruit.
Aggregate joints are formed from a single flower with an apocarpous pistil, carpel constitutes a fruit let. An example is kola nut. Again fruits can also be divided into two: fleshy and dry fruits.
(i) Fleshy or succulent fruits:
This group includes:
2. Hesperiditrm: This class of fruit is made up of distinct chambers of separated sheets of endocarp. The epicarp and mesocarp are fused together to form the skin. Seeds are embedded in each chamber. Examples are orange, lemon, lime, tangerine.
3. Drupe: Phis consists of a thin epicarp. fleshy or fibrous mesocarp and a stony or hard endocarp surrounding the see Examples are mango, coconut and palm fruit.
4. Pome: This consists of an outer covering and a fleshy edible part which are formed by the swelling of the receptacle. Examples are pear and apple.
5. Sorosis: This is a fleshy multiple false fruit which develop from a dense inflorescence. Every part of each flower forms part of the fruit while the peduncle swells to form the core. Example are pineapple and Jack fruit. DIAGRAM
Figure 2.4.2a: Internal Structure of Orange (Hesperidium) DIAGRAM Figure 2.4.2b: Internal Structure of Coconut (Drape) DIAGRAM Figure 2.4.2c: Pome (Peat) DIAGRAM Figure 2.4.2d:
(Pineapple) (ii) Dry fruits: These are fruits which have hard, dry pericarp.
This has one carpel which can split along two edges. Examples are cowpea, groundnut.
This has many joined carpels which split along all structures from base to the apex. Examples are okra, cotton.
This is a simple dry one seeded fruit which does not split open (indehiscent). Examples are maize, guinea corn, millet and other cereals.
This has a hard pericarp which can be broken or cracked. Examples are cashew nut, walnut, almond.
Advantages of sexual or seed propagation
1. It is very easy to practice. That is seeds can be carried conveniently to the farm 2. It brings about easy multiplication of plant population. 3. Well stored seeds can remain viable for a long time. 4. It is a sure way to start a disease free crop. 5. It can be used to improve crops through cross-breeding.
Disadvantages of sexual or seed propagation
1. Some crops take long time to mature and fruit when planted by seeds. Example is orange.
2. Some seeds are lost in the soil during propagation because of termites, rats and hare. 3. It is difficult to grow crops that are seedless with this method
Seed treatment before sowing:
1. Pre-soak the seeds. This is to allow some very hard secd to absorb water that will aid germination.
2. Scarification is carried out to loosen the surface of the seeds for easy emergence of the radical and plumule.
3. Chemical dressing of seeds. This is done so that disease organisms do not affect the seeds. It is also to prevent pests from destroying the seeds.
2. Asexual or vegetative propagation This involves the use of parts of plant in multiplying the plant, parts of plant such as roots, stem and leaves can be used instead of seeds. For example, the root can be used to grow breadfruit and potato. The leaf can be used to multiply the plant Bryophyllum.
Crops such as cassava and sugar-cane can be grown from stem. Methods of Asexual or Vegetative Propagation: There are several methods of asexual or vegetative propagation
These are: 1. Budding 4. Layering 2. Grafting 5. Marcotting 3. Cutting 6. Others. 1. DIAGRAM
1. Budding type of propagation
This is the bringing together of the bud and stock. The bud is taken from a tree already producing or matured. This forms the bud stick or slip. The stock is a young plant of about a year old.
During budding propagation, a T-shaped cut or inverted T-shaped is made at about 45 cm from the ground on the stem of the stock plant. The cut shape is slightly raised to expose the cambium.
The bud is carefully slipped into the raised bark and pressed firmly to ensure that the combination of both bud and stock unite together. It is tied with plastic material, or any device to hold it in place. This should be done quickly to prevent the bud from drying. Air and water should be prevented from the cut until the bud lies taken’ or heal together with the stock
This will show when the bud remains green. The bud then shoots after some days. When it becomes well established, the part of the stock above the bud should be cut-off. The cut surface should be to avoid fungal or bacterial infection. It is commonly used in citrus. .
2. Grafting propagation of crop
This is the union of the stock and scion. The part of the plant whose root is in the ground is called the stock while the stem removed from other plant is called scion. The scion is normally attached to the stock for grafting to take place.
The junction is rubbed with grafting wax to prevent trie entrance of air water and pathogens. It is advisable to water until when the wrapping may be removed after two weeks.
Advantages of budding and grafting:
3. Layering type of propagation of crop
This involves bending a shoot or branch of a plant to the ground so that the nodes can make contact with the soil. It is then pegged below the ground and covered with rich soil to provide good medium for root development.
When roots have emerged the branch is cut from the parent plant. This can be transplanted after a time as rooted cuttings. Layering can be used in coffee, cocoa and kola production. DIAGRAM Figure 2.4.5: Layering Method
4. Cutting type of propagation of crop
The plants produced, have the same characteristics as the original plant from which the cuttings were obtained. Cuttings can be obtained from soft wood as in sweet potato, semi hard wood as in cassava and hard wood as in hibiscus plant.
they should be cut from stems that have started to harden. The cutting should be about 20 cm long or convenient length, with two to three nodes or buds. It should be put into the ground to enable it have contact with the soil. It should be watered after planting or raised in shade during dry periods or planted during the rains.
5. Marcotting type of propagation
Marcotting is a practical vegetative propagation method. In this practice, the bark of a branch is peeled off with a knife, up to a considerable length. This should not be more than 5 cm long. Soil rich in organic manure is tied to the peeled portion by means of coconut husks or any suitable device.
6. Other methods: Some plants are grown or propagated means of suckers as in pineapple and plantain
, tubers as in yam, under-ground stem (corms) in cocoyam, bulbs in onion.
Vines (runners) in Irish potato. Some are grown from rhizomes as in grasses and ginger with horizontal underground stems, containing nodes and internodes. Also, the roots of plants can be used as is the case of breadfruit-and carrot and cut leaf as in the case of bryophyllum.
Advantages of vegetative propagation:
1. It enables crop to produce in very short time e.g. citrus.
2. Plants propagated vegetatively have uniform growth rate.
3. They can stand a more adverse environmental conditions e.g. poor soil.
4. Plants that do not produce viable seeds can be propagated by this method.
5. The offspring are identical to the parent plant always
6. It is easy to obtain planting materials.
7. Many flowers or ornamental plants are easily grown with the method.
1. It is sometimes very laborious because planting materials are bulky.
2. Diseases are easily transferred from parent to offspring.
3. Vegetative parts of plant cannot be stored for a long time for planting.
4. Genetic improvement of crop is impossible. STUDY QUESTIONS 1. Outline the various methods of crop propagation. 2. State Three advantages and disadvantages of seed or sexual propagation. 3. Enumerate Five types of vegetative propagation of crops.describe any Three of such methods. 4. State four advantages of budding and grafting as methods of vegetative propagation. 5. What are the advantages of vegetative propagation of crops? 6. Write short notes on the following: i. Vegetative propagation ii. Marcotting iii. Caryopsis iv. drupe 7. (a) Describe layering as a vegetative method of crop propagation. (b) Mention some crops that can be propagated by layering.
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HERE YOU WILL FIND EVERY AVAILABLE TOPICS ABOUT AGRICULTURAL SCIENCE AND BIOLOGY. AND THE LINKS TO THEIR VARIOUS SOURCES.
1. DEVELOPMENT OF AGRICULTURE
2. IMPORTANCE OF AGRICULTURE
3. SUBSISTENCE AGRICULTURE
4. COMMERCIAL AGRICULTURE
5. PROBLEM OF AGRICULTURAL DEVELOPMENT
6. SOLUTIONS TO POOR AGRICULTURAL DEVELOPMENT
7. AGRICULTURAL LAWS AND REFORMS
8. ROLES OF GOVERNMENT IN AGRICULTURAL DEVELOPMENT
9. AGRICULTURAL POLICIES
10. PROGRAM PLANNING IN AGRICULTURE
35. WILDLIFE CONSERVATION
36. FACTORS AFFECTING LAND AVAILABILITY