Plant Propagation.

Plant propagation is the creation of new plants from existing ones. There are two main types of plant propagation: asexual (vegetative propagation), sexual (seed propagation).

Genetic control in propagation – in vegetative propagation plants are genetically similar to their parents. this does not improve the genetic diversity. In sexual propagation plants offspring plants are genetically dissimilar to their parents, genetic variation and the diversity is increases.

Mainly there are two types of plants propagations

1. Vegetative propagation
2. seed propagation

Vegetative propagation

Reproduce progeny plants identical in genotype to a single source plants. also known as cloning. the main principle for that is the totipotency(a single cell becomes a entire plants)

Advantages of vegetative propagation

1. Identical offsprings to parent plants. therefore resulting progeny are true to type.
2. This can maintain the uniformity of the plant populations.
3. Preservation of desirable traits because offsprings are genetically similar to the parent plants.
4. Rapid production of a large number of plants in a short time period.
5. Feasibility for propagation of plants that produce little or no seeds
6. Suitable for propagation of plants during the unfavourable environmental conditions.
7. Preservation of superior genotype. (species that tolerant to abiotic and biotic stress.)

Methods of vegetative propagation

• Propagation by naturally present specialized vegetative structures (bulbs, corms, tubers, rhizomes, tuberous roots)
• Induction of adventitious roots or shoots (cutting, layerings)

Cutting – Regeneration of the vegetative parts detached from parent plant.

Stem cutting – Auxin produce in the soot tips and transport downward to the cutting and accumulate then induce the root development.

• Herbaceous cutting – coleus, chrysanthemum, 8 cm -13 cm length, no need of PGRs
• Soft wood cutting – Jasmine, 10-15 cm. leaves are reduce to prevent the desiccation, no need of PGRs
• Semi hardwood cutting – 7.5 cm – 15 cm length, PGRs are required.
• Hardwood – 10 cm -30 cm length, PGRs are required.

Leaf cutting

• leaf blade or leaf blade with petiole. – whole leaf cutting with petiole – African violet, split vein – Begonia
• Leaf bud cutting – Camelia, Blackberry

Root cutting – plant that derived from the root cutting are large and vigorous

• Plants with large roots – straight cut, after the 2 – 8 inches slanted cut, carryout in outdoor.
• Plants with small roots – straight cut, after the 1 – 2 inches slanted cut, carryout in indoor.

Layering – Regeneration of the vegetation parts while attached to the parent plant.

Ground layering – stem that has horizontal, close to the ground, contains one or few buds is selected, make a cut on the stem and covered with the soil.

Air layering – Target region is wounded / strip of bark is removed, apply the PGRs (if necessary), covered with the coir dust and wrapped by black polythene.

• Merge of plant parts by means of tissue regeneration (grafting, budding) Structural and physiological requirements for a successful grafting. Structural requirements – Compatibility (rootstock and scion should be from the same or closely related species.), Size and the shape scion and rootstock, cambial region of the scion must be placed in close proximity with the cambium of the stock.physiological requirements – The rootstock and scion both be healthy and vigorous, temperature – 24-29, moisture – high RH, dark – light is known to inhibit callus development

• Micropropagation (tissue culture)
• Asexual seeds productions. – seed development without fertilization, use for maintain the possible genotype throughout the population.

Micropropagation (tissue culture)

Tissue culture is the process that generation of new plant from the existing small plant tissue.

Main steps of the micropropagation.

• Explant collection – small piece of tissue, called an explant, is taken from the mother plant and sterilized to remove any contaminants and harmful microorganisms
• Callus formation – form a mass of cells called a callus
• Regeneration – callus is induced to form new shoots and roots.
• Hardening – new plants are growth under control environmental condition until transplanting in the field.

Micro propagation methods.

Meristem culture – Culture of apical or axillary shoot meristems. Steps – explant collection, callus initiation, shoot induction, root induction, hardening

Organogenesis – development of new organs, shoots and roots, from plant tissue. Steps – explant collection, callus initiation, organ initiation, hardening. For shoot production–Aux/CK <1, For root formation–Aux/CK >1

Somatic embryogenesis – An artificial process in which a plant/embryo is derived from
vegetative cells rather than from gametes. Steps – explant collection, callus initiation, embryo initiation, hardening.

Seed propagation

Seed propagation is the production of new plants from the seeds. the basic step of the seed propagation

1. Seed collection – seeds are collected and stored in dry and cool place.
2. Seed cleaning and treatment: remove any debris, remove any seed coat.
3. Sowing: The seeds are sown in containers, in the ground, depending on the type of plant.
4. Germination: The seeds will germinate and start to grow into young plants.
5. Hardening: new plants are growth under control environmental condition until transplanting in the field.

function of the seeds – contain the genetic material for the growth of a new plant, dormancy, food storage, protection for embryo and the stored foods, dispersal of seeds.

Advantages of seed propagation

• Produce large number of plants that are beneficial for large scale commercial products.
• improve genetic variability.
• Seeds are used to preservation of species.
• cost effective and easy to use.
• produce diseases free plants because viral diseases are not usually transmitted through seeds, relatively few seed–borne diseases

Disadvantages of seed propagation

• Dormancy
• Slow growth
• phenotypic variability among species can negatively impact on large scale productions.
• All seed will not germinate.
• Some rare plants seeds are difficult to obtain
• longer production time than the vegetative propagation.

Seed quality

Ability to seed to germinate and grow into healthy, vigorous plant.

seed quality is mainly determined by the physical, physiological, and genetic attributes.

Physical attributes – consider the size, shape, color, texture, and seed coat thickness

Physiological attributes – viability (ability of the germination under favorable conditions), germination rate, and vigor. Seeds viability test – standard germination percentage, TTC test, Training embryo Seeds vigor concern with higher storability, successful field emergence, ability to perform well over a wide range of field conditions

Genetic attributes – Storability is mainly a genetically regulated characteristic of seeds, depending on their storability and moisture content seeds can be divided into 2 groups

Orthodox seeds – Usually are medium or long lived seeds, exhibit tolerance to desiccation, longevity is extended by gradual reduction in moisture content and exposing to low temperature

Recalcitrant seeds – Often are short–lived seeds, can be germinated immediately after seeds
are released

Seed dormancy – seed will not germinate even environmental condition is favourable to germinate.

Seed dormancy is two types

Physical dormancy (Exogenous factors )- Due hard seed coat, can be removed by naturally and artificially. Natural – weathering, forest fire, microbial interactions, digestive track of the animals. Artificial – Mechanical methods (rubbing), Hot water (77⁰C-100⁰C for 30 min), burning, use corrosive chemicals.

Physiological dormancy (Endogenous factors) – presence of inhibiting – Dry storage (to remove the volatile inhibitors) stratification – low temperature or directed to water flows to remove the inhibition (ABA), plant growth regulators (cytokinin, gibberellin), embryo rescue.