π¨ββ€οΈβπβπ¨ Method of Propagation
Sexual, Asexual and Commercial propagation methods
ππ» Plants can be propagated by sexual and asexual means.
Sexual Methods of Propagation
- Propagation or multiplication of plants by seeds is known as βsexual propagationβ. Seeds are formed as a result of successful fertilisation and combination of parental gametes.
- It is an old and easy method and is widely used for the propagation of crops like ornamental annuals, vegetables, medicinal and fruit plants, such as papaya.
Merits of sexual propagation
- Plants propagated by seeds live longer, are vigorous and more resistant to biotic (insect-pests and diseases) and abiotic stresses (environmental conditions).
- It is an easy, simple and convenient method of plant propagation.
- Some plants like papaya, marigold, chilli, capsicum, tomato, etc., cannot be propagated by asexual method.
- It is the only means of creating genetic diversity of plants.
- New varieties and cultivars of ornamental and vegetable crops can be developed only by this method.
- A large number of rootstocks for budding and grafting purpose is also raised by this method.
- Seeds can be transported easily and stored for a longer time using this method.
Demerits of sexual propagation
- Sexually propagated plants show variations and are not genetically true-to-type to the mother plants.
- Plants that are propagated through seeds have long gestation period, which results in delayed flowering and fruiting.
- Plants grow vigorously and cause obstruction in intercultural practices like harvesting and spraying.
- Advantages offered by rootstocks and scion as in asexual propagation cannot be exploited through sexual method.
- Crop species, which do not produce seeds like pineapple, banana, strawberry, fig, jasmine, hibiscus, bougainvillea, etc., cannot multiply by this method.
Seed
- Seed quality is considered best if pure seed % is above 98%. Moisture content: 6-8% Germination %: 60-70%.
Dormancy
- Inability of viable seed to germinate.
- Hard seed coat dormancy: Ber, Guava, Walnut
- Dormancy due to presence of ABA β temperate fruits
- Seeds of tropical and subtropical fruits are sown during monsoon.
- In Walnut, Pecanut, Jackfruit, Ber-sowing of seeds in insitu is recommended.
- Orthodox seeds: Seeds remain viable for long time at low temperature.
- Recalcitrant seed: Seeds don’t remain viable for long time at low temperature. So they should be sown immediately after extraction.
- Example: 1.
Mango
2.Citrus
3.Litchi
4. Loquat 5. Mangosteen 6. Avocado 7. Jack fruit 8. Rambutan 9. Barbados Cherry
- Example: 1.
Methods to break dormancy
- Scarification: Process of breaking or softening the seed covering to make it permeable to water and gases.
- Mechanically: Ber, Walnut, Peach
- By Hot water: Guava, Strawberry
- By Acid: KNO3
- Stratification: Seeds are subjected to low temperature (Chilling temp) to break dormancy - Apple, Pear, Peach, Apricot
- Chemical treatment: Seeds are treated with 0.2% KNO3 (Potassium nitrate)
- Use of hormones: 1. 100-500 ppm GA; 2. Etheral (500 ppm) 3. BA (10-20 ppm) (F) Cryopreservation: Storage in liquid N, at - 196 Β°C temperature or liquid CO2 at 43 Β°C temperature.
- Cryoprotactants: 1. Glycerol 2. DMSO (Dimethyl-sulphoxide)
Asexual Methods of Propagation
- It is also called βvegetative propagationβ. The vegetative parts of a plant like leaf, stem, root or their modified forms are used for propagation.
- Most of the horticultural crops are commercially propagated by vegetative or asexual method of propagation.
- Most of the fruit crops are propagated by vegetative means.
- Types
- Cutting
- Layering
- Grafting
- Propagation by specialized organs
β Merits of asexual propagation
- Many fruit and ornamental plants that do not produce seeds are multiplied by this method.
- Plants propagated by asexual propagation are true-to-type genetically.
- By top working (using budding and grafting), old and economically low productive fruit plants can be converted into superior ones.
- Advantages offered by rootstocks and scion can be exploited through asexual method.
- Maturity is uniform and the plant gives quality yield.
- Plants propagated by asexual method are small in size, so spraying of chemicals and harvesting are easy.
- This method enables noble plant production, e.g., different colours of flowers in a single rose plant and different types of mangoes in one mango plant can be produced through asexual method only.
β Demerits of asexual propagation
- By vegetative propagation, new varieties cannot be developed.
- It requires specialised skills, so it is an expensive method of propagation.
- The life span of asexually propagated plants is short as compared to sexually propagated ones.
- These plants are more prone to biotic and abiotic stresses.
Tissue Culture (Micro propagation)
- It is a technique for growing plant tissues isolated from the parent plant in an artificial medium and controlled environment over a prolonged period under aseptic conditions.
- It is used on commercial scale in
banana
, gerbera, orchid, carnation, anthurium, etc. - It is based on the phenomenon of
totipotency
of a cell, which denotes the capacity of a plant cell to regenerate into a full-fledged plant having different organs. - Callus is produced on explant in vitro due to wounding and growth substances, either endogenous or supplied exogenous in the medium.
- By using this technique, a large number of
true-to-type
virus-free
saplings can be produced in a short span. - Types
- Callus culture
- Cell culture
- Meristem culture: Virus free plants are obtained
- Organ culture
- Protoplast culture
- Shoot tip culture technique produce female plant in
Banana
. - Micro Grafting:
Citrus
- Shoot tips and Micro-cuttings are highly suitable ex-plant for faster and disease free
grape
production.
Plant propagation by specialised organs
- Specialised organs are modified stems or roots, developing above the ground surface or underground, which may be used for multiplication of plants.
- In horticulture, bulbous ornamentals include bulbs, corms, tubers, tuberous roots and rhizomes.
Bulb
- Bulb is a specialised underground structure having a flat basal stem and surrounded by fleshy scales.
- E.g.,
Onion
.
Corm
- Corm is an underground modified solid or compressed
stem
oriented vertically in the side having nodes and buds. - E.g.
Gladiolus
etc.
Tuber
- It is an underground storage organ having special swollen modified
stem
orroots
. - E.g.
- Root tuber like dahlia, caladium, dioscorea, Jerusalem artichoke, etc. and
- Stem tuber like
potato
, begonia etc.
Rhizome
- A modified
stem
of some plant growing horizontally just below the ground surface - E.g.
ginger
etc.
Runner
- It is a modified stalk, which is creeping in nature, produced in the leaf axil and grows out from the parent plant.
- It grows horizontally along the ground, where roots are produced at the nodes, which can be used to produce new plants.
- E.g.,
Strawberry
(typical example) doob grass, chlorophytum, etc.
Sucker
- It is a special shoot arising from the root or stem portion of a plant below the ground level.
- E.g.,
Banana
, chrysanthemum (stem), Clerodendron splendens (root suckers), anthurium, etc.
Offsets
Date palm
Commercial propagation methods of major fruit crops
ππ» Plants can be propagated by sexual and asexual means.
Sexual Methods of Propagation
- Propagation or multiplication of plants by seeds is known as βsexual propagationβ. Seeds are formed as a result of successful fertilisation and combination of parental gametes.
- It is an old and easy method and is widely used for the propagation of crops like ornamental annuals, vegetables, medicinal and fruit plants, such as papaya.
Merits of sexual propagation
- Plants propagated by seeds live longer, are vigorous and more resistant to biotic (insect-pests and diseases) and abiotic stresses (environmental conditions).
- It is an easy, simple and convenient method of plant propagation.
- Some plants like papaya, marigold, chilli, capsicum, tomato, etc., cannot be propagated by asexual method.
- It is the only β¦
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