fabioclass

SEXUAL AND SEED PROPAGATION OF CROPS


1. Sexual or seed propagation
This method makes use of seeds. It is common with both se pollinated and cross-pollinated crops. It is sometimes the only possible way to propagate some crops like tomato, maize, rice, bearjl 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, okro, cocoa, palm, rubber, mango, cashew and guava.

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 rcproductive organ. It consists of the stigma which receives the pollen grains during pollination; style which connects the stigma to the ovart through which the pollen tube grows during the process of fertilizers: and the ovary which contains the ovules which develop Into seeds.
After fertilization, a zygote is formed from the ovule. This develops to form an embryo. The ovule eventually develops into the seeds, while the ovary which contains the ovule develops into a fruit. Therefore, a fruit can be described as fully grown, fertilized ovary containing fully developed ovules the seeds.



Classification of fruits: Fruits may be classified as simple, footpound, 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 fruitlets 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 fruittet. An example is kolanut.
Again fruits can also be divided into two: fleshy and dry fruits.
(i) Fleshy or succulent fruits: This group includes:
1. Berry: This has a fleshy pericarp with hard seeds which are embedded in the fleshy and pulpy endocarp. Examples are tomato and guava.


DIAGRAM
Figure 2.4.1 :Tomato fruits : Berry.

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: this consists of a thin epicarp. fleshy or fibrous mesoearp 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: Sorosis (Pineapple)

(ii) Dry fruits: These are fruits which have hard, dry pericarp. They include:
1. Legume: This has one carpel which can split along two edges. Examples are cowpea, groundnut.
2. Capsule: This has many joined carpels which split along all structures from base to the apex. Examples are okro, cotton.
3. Caryopsis: This is a simple dry one seeded fruit which does not split open (indehiscent). Examples are maize, guinea corn, millet and other cereals.
4. Nut: 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 pfarrt 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 secdi 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 plmule.
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.


Budding: 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 vear old.

During budding, 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 cambia 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 lias taken' or heal together with the stock. This wtll 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 b'e to avoid fungal or bacterial infection. It is commonly used in citrus.


DIAGRAM

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