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Plants are propagated by two methods: 1. Sexual propagation or seed propagation. 2. Asexual or vegetative propagation by vegetative plant parts like root, stem, leaf etc.
Seeds can be defined as a dormant plant which develops into a complete plant subjected to required environmental conditions.
Germination of seed –
The activation of the metabolic machinery of the embryo leading in the emergence of a new seeding plant is known as germination. Germination is essentially a quickening of the growth of the embryo. As germination proceeds, the growing points of the radical and plumule divide rather rapidly. Usually the radical emerges from the seed coat first, proceeds downward, and develops into the root system, the plumule proceeds upward and develops into the shoot system. Germination is entirely a food utilization process. Processes going on in seed during germination are: 1) Absorption of water; 2) Secretion of enzymes and hormones; 3) Hydrolysis of stored food into soluble form; and 4) Translocation of soluble foods and hormones to the growing points. These processes are either wholly, or in part influenced by the food reserves, hormone supply, water supply, oxygen supply and temperature level.
Advantages of Sexual Propagation :-
1) This is very simple and easy method of propagation. 2) Some species of trees, ornamental annuals and vegetables which cannot be propagated by asexual means should be propagated by this method. E.g. Papaya, Marigold, Tomato etc. 3) Hybrid seeds can be developed by this method. 4) New variety of crops are developed only by sexual method of propagation. 5) Root stocks for budding and grafting can be raised by this method. 6) The plants propagated by this method are long lived and are resistant to water stress. 7) Transmission of viruses can be prevented by sexual method. 8) Seed can be transported and stored for longer time for propagation.
Disadvantages of sexual propagation :
- 1) Characteristics of seedling propagated by this method are not genetically true to type to that of their mother plant. 2) Plants propagated by sexual method requires long period for fruiting. 3) Plants grow very high, so they are difficult for intercultural practices like spraying, harvesting etc. 4) The plants which have no seeds cannot be propagated by this method. E.g. Banana, fig, Jasmine, Rose etc.
It is also called as vegetative propagation as it involves only vegetative parts without any sexual plant parts. The plant parts like leaf, stem, root and other root producing plant organs are used. The new individual propagated through this method is true to type. The commercially important fruit crops are propagated by vegetative method.
Types of vegetative propagation
1. Plants parts separated from mother plants.(Cuttings) Types of cuttings: A) Stem cutting: 1) Hardwood cutting - Fig 2) Semi hardwood cutting - Hibiscus 3) Softwood cutting - Pilia B) Leaf cutting - Begonia C) Root cutting. - Curry leaf 2. Still attached to mother plant. A) Layering: 1) Simple layering - Guava 2) Tip layering - Goose berry 3) Mound layering - Apple 4) Serpentine layering - Jasmines B) Air layering (Gootee layering) -Thuja C) Suckers - Banana D) Runners - Straw berry 3. Separated modified parts from mother plants: A) Separation: 1) Corm - Gladiolus 2) Bulb - Tube rose A) Division of plant parts: 1) Stem Tubers - Potato 2) Tuberous roots - Asparagus 3) Rhizome - Ginger 4. Grafting: 1) Approach grafting / inarching - Sapota 2) Stone grafting - Mango 3) Side grafting - mango 4) Root grafting - 5) Bridge grafting - 6) Butters grafting - 7) Cleft grafting - 8) Softwood grafting - 9) Tongue grafting / whip grafting – 5. Budding: 1) Shield / ‘T’ budding - Rose 2) Patch budding - Ber 3) Ring budding - Ber 4) Flute budding 5) Chip budding 6) Forkert budding 6. Tissue Culture – Banana, Gerbera, Carnation
Advantages of Asexual propagation
1. The horticultural crops which donot produce viable seeds are propagated by vegetative method. 2. Most of the important fruit crops are cross pollinated and are highly heterozygous. When propagated through seeds, the progenies shows large variation, so vegetative propagation is remedy for these crops. 3. The asexual propagation method gives true to type plants. 4. The vegetative way propagated plants bear fruits early. 5. In case of fruit crops where root stocks are used, the root stocks impart insect or disease resistance to the plant. 6. Vegetative propagation helps to alter the size of the plant. i.e. dwarfing effect. This helps for spraying, intercropping & harvesting of crops easy and economical. 7. By grafting method different variety of fruit crop can be grown & harvested. 8. Inferior quality fruit plants can be converted into good quality plants. 9. By means of bridge grafting a repairing of injured plants can be done.
Disadvantages of the vegetative propagation:
1. By vegetative propagation new variety can not be developed. 2. It is an expensive method of propagation and required specialized skill. 3. The life span of vegetatively propagated plants is short as compared to sexually propagated plants. 4. As all the plants are homozygous the whole plantation may get attacked by a particular pest or disease. 5. Viral diseases could be transferred through vegetative parts.
A Fill in the blanks: 1. Asexual propagation is also known as propagation. 2. In Banana method of propagation is used on commercial scale. 3. Shield budding is practiced in fruit crop.
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