Plant tissue culture propagation, also known as micropropagation, involves several key steps to multiply or “proliferate” plants. Here’s a detailed description of how plant tissue culture seedlings are multiplied:

1. Selection of Explant: The first step is selecting the plant tissue (explant) from a healthy donor plant. Common explants include leaves, stems, roots, meristems, or buds. The explant is usually small and sterile.

2. Sterilization: The explant must be sterilized to remove contaminants like fungi or bacteria. This is done using chemical agents such as sodium hypochlorite or ethanol. After sterilization, the explant is placed in a sterile environment, typically under a laminar flow hood.

3. Callus Induction: Once the explant is sterilized, it is placed on a nutrient medium that contains the necessary minerals, vitamins, and plant growth regulators (like auxins and cytokinins). These regulators help induce cell division and the formation of callus tissue, a mass of undifferentiated cells. Callus formation is critical because these cells have the potential to differentiate into any part of the plant.

4. Shoot Induction: After the callus is formed, the nutrient medium is changed or supplemented with plant hormones (usually a higher ratio of cytokinins to auxins) to induce shoot development. Multiple shoots may arise from the same explant, allowing for rapid multiplication.

5. Shoot Proliferation: The newly developed shoots can be excised from the culture and subcultured onto fresh media to further increase the number of shoots. This process can be repeated multiple times, leading to exponential growth in the number of shoots.

6. Root Induction: After a sufficient number of shoots have been generated, they are transferred to a medium with a higher concentration of auxins, which promotes root development. Once the shoots develop roots, they are considered plantlets.

7. Acclimatization: The plantlets are then transferred from the in vitro environment (culture medium) to soil or a controlled growth environment (such as a greenhouse) for acclimatization. This step is critical, as the plantlets need to adjust to natural growing conditions like varying humidity, temperature, and light.

By repeating this cycle of shoot multiplication, a large number of plants can be produced from a small piece of tissue, which is the key advantage of plant tissue culture over conventional propagation methods.

This method is widely used in agriculture, horticulture, and forestry to produce uniform, disease-free, and genetically identical plants.