What is the process of micropropagation using tissue from the shoot apex, nutrient agar gels, and growth hormones?

Sourav PanNovember 9, 2024

Answered

Micropropagation is a tissue culture technique that enables the rapid vegetative propagation of plants using small tissue samples, typically from the shoot apex. This method is widely used for producing large numbers of identical plants (clones) under controlled laboratory conditions. Here’s a detailed overview of the process of micropropagation using tissue from the shoot apex, nutrient agar gels, and growth hormones:

Steps in Micropropagation

1. Selection and Preparation of Explant

• Explant Selection: The process begins with selecting a healthy stock plant. The shoot apex, which contains undifferentiated meristematic cells, is commonly chosen as the explant due to its potential for continuous growth and organ formation.
• Surface Sterilization: The selected shoot apex is carefully excised and subjected to surface sterilization to eliminate contaminants such as bacteria and fungi. This typically involves soaking the explant in a solution of bleach or ethanol followed by rinsing with sterile water.

2. Culture Initiation

• Placement on Nutrient Agar Gel: The sterilized explant is placed on a sterile nutrient agar gel medium. This medium provides essential nutrients, vitamins, and minerals required for plant growth. Agar serves as a gelling agent that stabilizes the medium and allows for easy handling of the explant.
• Composition of Medium: The nutrient medium often includes macronutrients (such as nitrogen, phosphorus, potassium), micronutrients (like iron and manganese), and organic compounds (such as sucrose) to support growth.

3. Application of Growth Hormones

• Auxins and Cytokinins: Growth hormones play a crucial role in regulating plant development during micropropagation. Auxins (e.g., indole-3-acetic acid or IAA) are typically added to promote root formation, while cytokinins (e.g., benzylaminopurine or BAP) stimulate shoot multiplication.
• Hormonal Ratios: The ratio of auxins to cytokinins in the medium can influence whether the explant develops roots or shoots. A higher concentration of cytokinins relative to auxins tends to promote shoot formation, while higher auxin concentrations encourage root development.

4. Shoot Multiplication

• Induction of Shoots: Under optimal conditions (controlled temperature, light intensity, and humidity), the explant begins to develop multiple shoots from the meristematic tissue. This stage is characterized by rapid cell division and elongation.
• Subculturing: Once shoots are established, they can be subdivided and transferred to new agar media to promote further multiplication. This process can be repeated several times to produce numerous shoots from a single explant.

5. Rooting Phase

• Root Induction: After sufficient shoot multiplication, the shoots are transferred to a rooting medium that typically contains higher concentrations of auxins to encourage root development.
• Monitoring Root Growth: Roots begin to form after several weeks, and their growth can be monitored to ensure healthy development.

6. Acclimatization

• Transfer to Soil: Once the plantlets have developed sufficient roots and shoots, they are carefully removed from the agar medium and transplanted into pots containing soil or a suitable growing substrate.
• Gradual Acclimatization: The young plants are acclimatized gradually to external environmental conditions (light, humidity, temperature) to reduce transplant shock.