Micropropagation | Botany Optional for UPSC PDF Download

Micropropagation is an artificial process used for the vegetative reproduction of plants through tissue culture or cell culture techniques. In this method, plants are cultivated in a controlled, laboratory setting by means of asexual reproduction or vegetative propagation.

Plants can be reproduced using both asexual methods, such as the multiplication of vegetative parts, and sexual methods, which involve seed production. Asexual reproduction allows for the creation of genetic replicas of plants and is often referred to as clonal propagation. With clonal propagation, numerous plants can be derived from a single parent plant through asexual means of reproduction.

In cases where certain plants do not produce functional seeds, as is the situation with plants like figs, grapes, and bananas, asexual reproduction through the multiplication of vegetative parts becomes the primary method for propagating these plants. Clonal propagation has been successfully applied to various plants, including potatoes, apples, and numerous ornamental plant species.

Methods of Micropropagation

Micropropagation involves five distinct methods for artificially producing plantlets:

• Meristem Culture: In this method, a combination of the subtending leaf primordial and a meristem is placed into their respective culture media and allowed to grow. Over a few weeks, elongated plantlets with roots are produced. Once they reach a suitable size, these plantlets can be transplanted into soil. This method is valuable for generating disease-free plants and rapidly multiplying various herbaceous species.
• Callus Culture: This technique involves placing selected plant tissue in an artificial culture medium until callus (undifferentiated tissue) forms. After callus formation, it is transferred to a culture medium containing plant growth regulators to induce the development of adventitious organs. Over a few weeks, the resulting plantlet is gradually exposed to environmental conditions.
• Suspension Culture: In suspension culture, plant cells or cell groups are dispersed and allowed to grow in an aerated, sterile liquid culture medium.
• Embryo Culture: In this method, embryos are extracted and placed in a culture medium with the appropriate nutrients under aseptic conditions.
• Protoplast Culture: Protoplast culture involves isolating plant cells and culturing them in a suitable medium to regenerate the cell wall and form callus. Under suitable conditions, the cells develop cell walls, undergo increased cell division and cellular differentiation, ultimately growing into new plants. This method is particularly useful for genetic transformation and regeneration of plants with specific traits.

Stages of Micropropagation

Micropropagation typically consists of several stages, each with its specific tasks and objectives:

Stage 0: Initial Preparation

• Select stock plants and grow them under controlled conditions to ensure their health and vigor, as they will be used as the source of explants for culture initiation.

Stage I: Culture Initiation

• Isolate the explants (small sections of plant tissue) from the selected stock plants.
• Conduct surface sterilization to eliminate contaminants.
• Rinse the explants to remove any residual sterilizing agents.
• Establish the explants on an appropriate culture medium that provides the necessary nutrients and growth regulators to initiate growth.

Stage II: Shoot Multiplication or Somatic Embryo Formation

• In this stage, the explants are subjected to conditions that promote the rapid multiplication of shoots or the formation of somatic embryos.
• The culture medium is carefully formulated to support this proliferation.

Stage III: Root Development

• Once a sufficient number of shoots or somatic embryos have been produced, they are transferred to a medium that stimulates root development.
• Roots can either be induced in vitro on the nutrient medium or the shoots may be transplanted directly into soil for root growth.

Stage IV: Acclimatization and Establishment

• At this stage, plantlets with well-developed roots are transferred to a greenhouse or controlled environmental conditions.
• The greenhouse provides the necessary conditions, including temperature, humidity, and light, to facilitate the acclimatization of the plantlets to a soil-based environment.
• Throughout these stages, careful monitoring and maintenance of environmental conditions are critical to ensure the successful growth and development of the micropropagated plants.

Advantages of Micropropagation

Micropropagation offers several advantages in plant production:

• Enhanced Multiplication Rate: Micropropagation serves as an alternative method for vegetative propagation, significantly increasing the rate of plant multiplication.
• Rapid Multiplication: Large quantities of identical plants can be generated from a single piece of plant tissue within a short time frame.
• Short Cycle for Shoot Multiplication: The process of shoot multiplication has a short cycle, resulting in a logarithmic increase in the number of shoots with each cycle.
• Easy Storage and Transportation: Small-sized propagules can be easily stored and transported.
• Long-Term Germplasm Maintenance: Germplasm stocks can be maintained for several years using this technique.
• Pathogen-Free Varieties: Micropropagation allows for the production and maintenance of pathogen-free plant varieties.
• Controlled Sex Determination: In dioecious plants, where the seed progeny yield is typically 50% male and 50% female, this method helps obtain the desired sex of the plant.
• Compact Storage: Millions of plantlets can be efficiently maintained in cultural vials.
• Genetic Uniformity: Micropropagation ensures genetic uniformity of the propagated plants.
• Cost-Effective: It is a cost-effective process, especially for mass production of plants.
• Variety Propagation: New varieties of species can be propagated with precision.
• Space and Resource Efficiency: Micropropagation requires less space and fewer human resources compared to traditional methods.
• Year-Round Availability: This method is independent of seasonal constraints and can be carried out at any time of the year.
• Regeneration of Genetically Modified Cells: Micropropagation assists in regenerating genetically modified cells after protoplast fusion.
• Healthier Plants and Quicker Growth: Plants produced through micropropagation are often healthier and exhibit faster growth compared to those produced using conventional methods.

Disadvantages of Micropropagation

Micropropagation, while advantageous, also has its disadvantages:

• Non-Autotrophic Plants: Plants produced through micropropagation are typically non-autotrophic, meaning they may require additional support or nutrients to establish themselves in natural environments.
• Limited Applicability: Micropropagation cannot be implemented for all plant species or crops, as some may not respond well to the tissue culture conditions or may not be amenable to this method.
• Acclimatization Challenges: The plantlets produced through micropropagation can face difficulties when transitioning to the natural environment. This process, known as acclimatization, can be challenging and may require special care to ensure the plantlets successfully adapt to outdoor conditions.

Key Points of Micropropagation

Here are the key points to understand about micropropagation:

• Definition: Micropropagation is a plant propagation technique involving the growth of plantlets in tissue culture followed by their transplantation into soil.
• Desired Characteristics: It allows for the production of plants with specific and desired characteristics.
• Stepwise Process: Micropropagation is a stepwise process that results in the generation of a large number of plants from a single explant (a piece of plant tissue).
• Genetic Uniformity: The plants produced through micropropagation are genetically identical to the parent plant.
• Stages: The process involves several stages, including the establishment of the explant, multiplication of the explant in a culture medium, transfer of growing shoots into a medium for shoot development, transferring the plant into soil for root growth, and allowing the growth and development of plants under optimal conditions.