Artificial vegetative propagation: The process of producing many new plants form the vegetative parts of a single plant artificially is called artificial vegetative propagation. It is done by cutting, layering, grafting, tissue culture etc.
1. Cutting: In this method, a branch of plant is cut by using sharp knife and the branch is buried partially in soil. After sometime, roots are developed in the underground part and it develops into new plant. This method is common in rose, hibiscus etc
2. Layering: The technique of producing roots in a branch of a plant by inserting some of its stem in the soil when it is attached with parent plant to form new plant is called layering. There are various methods of layering. They are:
a. Simple layering: In this Technique old lower branch of plant is bent and buried. Some of their stem in ground after few months roots are formed in buried part. Now it is separated from parent plant and used as new plant. Eg, in lemon, Nibuwa etc
b. Compound layering: In this method, the maximum part of on old branch is inserted into soil, leaving the apex in air, new plants grow from different nodes which are then separated from parent plant. Eg, apple, pear, walnut etc.
c. Tip layering: In his technique, tip of the branches are inserted in soil. After sometime, roots and shoots are formed in the tip now it can be separated from parent plant and used as new plant. This technique is suitable for plants like blackberry.
d. Mound or stool layering: In this technique, stem of a tree is cut from about 15cm above the ground in spring season. Many new buds start growing from the stem. Some of their portion is covered with soil and hummus. After some time, roots are developed in these branches. Now, they can be separated from parent plant and used as a new plant. This technique is suitable for heavy stemmed trees with tight branches mango, guava, plum etc.
e. Air layering: In this technique, at least 1 year old branch is selected and its bark a removed for about 10cm length in the form of ring. It is covered with grafting clay and wrapped with polythene sheet. After few months, roots appear inside the polythene. Now, it can be separated from parent plant and used as a new plant This method is suitable for plants like manga, papaya, citrus fruits etc.
3. Grafting: It is the technique in which a part of one plant is transplanted to other plant of closely related varieties.
Stock: The part of plant with root system used during grafting is called stock.
Scion: The part of plant which is grafted is called scion. It is the part of old branch.
There are various methods of grafting
a. Whip grafting: In this method, stock and scion of similar size and diameter are selected. Slanted cut of about 3.5 cm is made in both scion and stock. Both parts are kept together tightly so that both the cut face match closely. It is wiped with plastic and made air tight After few month they join together forming a single plant.
b.Tongue grafting: In this technique, scion and stock of similar diameter are selected, slanted cut is made for about 3cm in both of them along with fissure about 1cm depth. Cut parts of scion and stock are fixed together and made air tight by wrapping plastic which can be removed later.
c. Saddle grafting:
d. Cleff grafting: In this method, stock is cut and about 5 to 8cm deep fissure is made in lower part of scion is cut in V shape and fixed into fissure then it is covered with grafting wax, after few months both scion and stock are fused together.
Tissue culture: It is modern technique of reproduction in which tissue of a plant is grown in an artificial medium ta generate new plants.
Method: Artificial medium that is mixture of Nitrogen, auxin, and cytokinin is prepared in balanced condition. Some tissues of selected plant are cultured in this medium, after few days tissue grows into unorganized mass called callus.
Callus is divided into many pieces and kept in another culture medium where roots, and shoots are grown and plantlets are formed these plantlets are transferred into soil for independent growth.
Advantages of tissue culture.
- Numerous new plants can be produced in industrial scale which are generally similar to parent plant.
- Endangered plants con be preserved.
- It helps to minimize chances of transmitting diseases and pathogens.
Solve exercise
a. What is the role of chemicals auxin and cytokinin in tissue culture?
Auxin stimulates growth of root and cytokinin stimulates growth of shoots.
b. What is callus?
It is an unorganized mass of tissue which is formed due to culture of a tissue in an artificial medium.
c. What is layering? What is the best time of year for layering?
The process of growing a new plant from branch of a parent plant by growing roots on it is called layering. The best time of the year for layering is spring season.
d. Mango plant grown by grafting is better than the not grown from seed. Justify?
It is because when new plant is prepared from grafting, parental characters on be preserved. It gives production in short time period, desirable quality can be obtained but not in the one grown from seed.
e. Write any 2 differences between layering and grafting.
| Layering | Grafting |
| It is technique of producing roots in a branch of a plant by insertion of its stem in soil when it is attached with parent plant to form new plant. | It is the technique in which part of one plant is transplanted to other plant of closely related varieties. |
