Methods of cultivation
Medicinal plants can be cultivated by two methods (applicable to non-medicinal plants) : Sexual and Asexual method
Sexual Method (seed propagation):
In this method, the plants are raised from seeds. Such plants are known as seedlings. Seeds are sown in the fields by methods like broadcast, dibbling, or placing them in drills or holes. The seeds must be of good quality, capable of high germination rate, and free from diseases.
ADVANTAGES:
Seedlings are comparatively much cheaper and easy to raise.
Seedlings are long-lived, bear more heavy fruits and plants obtained are more sturdy.
In those plants where other methods of cultivation cannot be utilized, seed propagation becomes the only method of choice.
There are chances of production of some chance-seedlings of very high superiority which may be of great importance for e.g., orange, papaya, etc.
DISADVANTAGES:
The seedlings obtained from this method require more time to bear and are not uniform in their growth and yielding capacity as compared to other methods like grafting.
Also, the cost involved in harvesting and protection from pests is more.
Asexual Methods (vegetative propagation):
In this method, any of the vegetative part of the plant like root or stem is provided such an environment that it develops into a new plant. The environment is provided by setting various parts of the plant in well prepared soil.
Bulbs: A bulb is originally and structurally a bud, which possesses the capability of perennation. It consists of a very short stem ending in an apical meristem and enclosed by closely set leaves, which are thick and fleshy , being stored with reserves of food. Each of the leaves has of course its axillary bud .
After flowering , the foliage leaves persist for a time, forming food materials, which are now stored in one or more of the axillary buds. The axillary buds thus used as store houses become the bulbs of the new generation. Evidently, whenever more than one new bulb is formed from an old one, there has been vegetative reproduction as well as perennation e.g., Squill, garlic.
Corms: In a corm, the storage organ is swollen base of the stem and this is wrapped in thin scale-leaves, each of which, of course, has an axillary bud e.g. colchicum, saffron.
Tubers: It is a swelling on an underground stem branch. The stem grows axillary buds formed low down on the aerial stem and push through the soil, swelling at their ends to form the tubers. The ‘eyes’ of the tuber are very small scale-leaves, each with three axillary buds e.g., jalap, aconite, potato.
Rhizomes: In underground stems, the older parts of rhizome die off. The buds borne on the detached younger portions thus become separate new plants e.g., ginger, turmeric.
Runners: The stem grows along the ground (horizontally over the surface of the soil), and produces roots and erect flowering shoots from lateral buds at many of its nodes. The growth of the creeping stem is continued by the terminal bud. Some of the older internodes die, and the detached rooted and shoot bearing parts become independent plants e.g., peppermint, strawberry.
Suckers: A shoot arising from a root of a woody plant e.g., mint, pineapple, banana.
Offsets: These originate from the axil of the leaf as short thick horizontal branches and also characterized by the presence of rosette type of leaves and a cluster of roots at their bottom e.g., aloe, valerian.
Stolons: A creeping stem that roots at nodes e.g., arrow-root, liquorice.
Other methods,
Cutting: A clear cut is made preferably below the node and the lower leaves are removed. It is then placed in a suitable medium and provided with suitable conditions of moist atmosphere, temperature which favouring the development of roots e.g., mint, vanilla.
Layering: A layer is a branch or a shoot which is induced to develop roots before it is completely severed from the parent plant. It is done by a cut or ligature and embedding the part so treated in the soil e.g., cascara.
Grafting and Budding: Grafting is a process in which two cut surfaces of different but closely related plants are placed so as to unite and grow together. The rooted portion is called the stock and the cut off is the scion or graft e.g., female scion of Myristica fragrans on male stock to increase fruit bearing proportion.
Budding consists of the introduction of a piece of bark bearing a bud into a suitable cavity or ‘T’ shaped slit made in the bark of the stock e.g., citrus species, sweet and sour oranges.
Aseptic methods of propagation: In this method, the plants are developed in an artificial medium under aseptic conditions from very fine pieces of plants like single cells, callus, seeds, embryos, root tips, shoot tips, pollen grains, etc. They are provided with nutritional and hormonal requirements.
ADVANTAGES (Asexual method):
There is no variation between the plant grown and plant from which it is grown. As such, the plants are uniform in growth and yielding capacity.
Seedless varieties of fruits can only be propagated vegetatively e.g., pomegranates, grapes, lemon.
Plants start bearing earlier as compared to seedlings.
Budding or grafting encourages disease-resistant varieties of plants.
DISADVANTAGES:
In comparison to seedling trees, these are not vigorous in growth and are not long lived.
No new varieties can be evolved by this method.
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