Micropropagation: Definition, Introduction, Parts, Structure, Characteristics

What Is Micropropagation?

Micropropagation is one of the techniques of plant propagation in which the in vitro culture of tissue cultures of plants helps produce a large number of plants with identical genetic makeup from only a small piece of plant tissue. It uses the totipotency of the plant cells, which provides the capacity for plant regeneration into a whole plant in controlled laboratory conditions.

Micropropagation techniques in agriculture and horticulture help raise high-quality and disease-free plant varieties in many folds. The technique is utilised in the conservation course of the rarest and most endangered plant species and finds application in the large-scale production of ornamental plants and crops with genetic modifications.

Micropropagation allows for the mass production of uniform and disease-free plants, hence ensuring that elite plant varieties increase quickly. This helps in the conservation, and production of pathogen-free plants, and the propagation of plants that are difficult to grow through conventional means.

Principles Of Micropropagation

The micropropagation technique is based on two principles: cellular totipotency and the requirement of sterile aseptic conditions.

Cellular Totipotency

• Each plant cell is capable of regenerating into a whole plant.

• Requires proper conditions and growth regulators.

• Explants can be any plant part including leaves, stems, or roots.

Aseptic Techniques

• Bound to prevent contamination.

• Encompasses surface sterilisation of explants and also includes sterile instruments.

Sterile Environment

• Culture vessels, media, and tools are sterilised

• Laminar flow chambers are used to provide a sterile environment.

Stages Of Micropropagation

In micropropagation, there are four main stages of the process.

Stage 1: Initiation Phase

• Selection and Preparation of Explants: A healthy and disease-free plant is selected for the regeneration experiment.

• Surface Sterilisation Methods: These methods include ethanol or bleach as chemicals for surface sterilisation of explants.

• Culture Medium Composition: Nutrient-rich media are used, for example, Murashige and Skoog medium.

Stage 2: Multiplication Phase

• Subculturing Techniques: Regular transference to new media to promote growth.

• Cytokinins and Auxins in Shoot Proliferation: Use of plant hormones versus endogenous systems for the induction of shoots and multiplication.

Stage 3: Rooting Phase

• Induction of Roots: Adjusting the concentration of hormones to induce roots.

• Application of Rooting Hormones: Auxin treatment to induce rooting.

Stage 4: Acclimatisation Phase

• Transfer to Soil: Transplantation of plantlets from in vitro to soil.

• Hardening Techniques: Render the plants tolerant of unfavourable exogenous conditions.

Methods Of Micropropagation

Micropropagation consists of several techniques.

Organogenesis

• The induction of shoots and roots from explants.

Somatic Embryogenesis

• Production of embryos from somatic cells may give rise to complete plants. Meristem Culture

• Long-term culturing of meristematic tissues to obtain virus-free plants.

Callus Culture

• Cultivation of undifferentiated cell masses, called callus, capable of differentiating into plants.

Media Used For Plant Tissue Culture

Cultural media are utilised that depend on the type of plant and stage of development.

Murashige and Skoog (MS) Medium

• Components and Preparation: It contains macronutrients, micro-nutrients, vitamins, and growth regulators.

Gamborg's B5 Medium

• Applied for the culture of certain types of plants at specific stages in their development.

Woody Plant Medium (WPM)

• Formulated for culturing woody plant species.

Factors That Affect Micropropagation

Factors Affecting Success of Micropropagation

Genotype Of The Plant

• Explant Source and Type: Response to culture conditions may vary with different parts of the plant.

• Culture Medium Composition: Nutrients and hormones should be in proper balance.

• Environmental Conditions (Light, Temperature, Humidity): Optimum for growth and development.

Applications Of Micropropagation

The applications of micropropagation in plant sciences are many.

Clonal Propagation Of Elite Varieties

• Production of Disease-Free Plants: Culture of healthy and pathogen-free plant stocks.

• Germplasm Conservation: It preserves the genetic diversity of rare and endangered species.

• Genetic Transformation and Research: It facilitates genetic engineering and breeding programs.

Advantages And Disadvantages Of Micropropagation

Micropropagation has advantages as well as limitations.

Advantages

• Rapid Multiplication, Uniformity, Disease-Free Plants

• Under this method, large numbers of plants can be produced within a very short period.

• Clonal propagation ensures the production of identical plants.

• It produces plants free from pathogens.

Disadvantages

• High Cost, Technical Expertise, Risk of Somaclonal Variation

• It requires a special type of equipment and trained personnel also.

• It requires expertise in the area of tissue culture techniques.

• However, genetic variation can also occur in culture.

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