Plant kingdom includes enormous types of plants. Some of them multiply by seeds while some by vegetative plant parts and some of them use both means for multiplication. One finds similarity or likeliness in characteristic of vegetative progenies while variation in sexually multiplied population.
Seed propagation is the major tool in crop production. Higher plants reproduce naturally by seeds. Seedlings are extensively used in nurseries to provide rootstocks upon which grafting or budding is done. In plant breeding, growing of seedling is the most important means of developing new cultivars. There are different techniques in seed production of fruit trees, vegetables, and ornamental plants. Production of hybrid seed is highly technical and time consuming process.
Vegetative propagation is called asexual propagation and has special importance in keeping uniformity amongst offsprings and obtaining early production. It is the only way of propagation in certain plant. Stock and scion both are important and vary according to need and convenience. Considerable skill at various stages during propagation and after care is highly necessary. This is the only method to establish a new orchard in situ, renovate old unproductive orchard or convert undesirable varieties into desired one.
Sexual Plant Propagation
Sexual plant propagation involves the union of the pollen (male organ) with the egg (female organ) in plants to produce a seed. The seed is made up of three parts: the outer seed coat, which protects the seed; the endosperm, which is a food reserve; and the embryo, which is the young plant itself. When a mature seed is exposed to favorable environment, it germinates and begins its active growth.
Advantages of Sexual Plant Propagation
1. It is the easiest and least expensive method of plant propagation.
2. Seedling trees are hardier and have longer life span.
3. Plants which are difficult to propagate by vegetative method e.g. papaya, phalsa, coconut etc. can only be propagated by seed.
4. The rootstocks on which the fruit varieties are budded or grafted are usually obtained by means of sexual propagation.
5. Sexually propagated plants are more resistant to pests and disease.
6. Large number of plants can be produced at a time by this method.
7. Polyembryonic varieties (give rise to more than one seedling from one seed) can be propagated by seed eg. Nucellar Embryo in Nucellar Mosambi (Sweet Orange)
Disadvantages of Sexual Plant Propagation
1. Seedlings take more time to bear fruits (late bearing).
2. Quality of existing plants cannot be improved by sexual propagation.
3. Plants propagated sexually are large in size, thus the cost of manuring, pruning and spraying increases.
4. In case of sexually propagated plants, there is no assurance about genetic purity of the offspring or seedling.
Asexual Plant Propagation
In this method the vegetative parts of plants such as leaves, stems, and roots are used for propagation. These plants may be taken from single mother plant or other plants. It is also called as vegetative method of plant propagation.
Advantages of Asexual Plant Propagation
1. Plants propagated by this method are true to type and uniform in growth, yield and quality of fruits.
2. Some fruits such as Banana, Pineapple, seedless Guava and seedless Grape varieties can only be propagated through vegetative means.
3. Vegetatively propagated fruit tree comes into bearing earlier than seed propagated plants and have assured genetic configurations.
4. Plants produced are of manageable size and have uniform fruits making harvesting easy.
5. Some diseases can be avoided in susceptible varieties by grafting them on a resistant rootstock e.g. Use of „Rangpur Lime‟ as rootstock for budding Mandarin Orange to avoid gummosis disease.
6. Better rootstock can be conveniently combined with the method to suit the climatic requirement of the area.
7. Repairing of damaged portion of plant is possible by asexual methods through bridge grafting or buttressing. These methods can be used for healing of the wounds caused by rodents.
8. Inferior quality crown of the existing plants can be improved. For example, side grafting and crown grafting in mango.
9. It is possible to grow multiple varieties on the same plant. One can grow numerous varieties of Roses and Mangoes on different branches of the same stock.
10. Number of plant per hectare is more due to its small canopy and restricted growth.
11. Vegetative propagation helps in rapid multiplication with modern techniques like tissue culture and other micro propagation techniques.
Disadvantages of Asexual Plant Propagation
1. It is difficult and more expensive method of propagation in some plants like papaya, coconut, etc. 2. Plants are generally not so vigorous and long lived as seedling plants and they require special skill for propagation.
3. Hybridization in these plants is not possible because there is no variation in the progeny; these methods are not suitable for development of a new variety.
4. Plants propagated by this method are not hardy and fall easy prey to adverse conditions of soil, climate, diseases, pests, etc.