Model Answer
0 min readIntroduction
Gladiolus, a popular ornamental bulb, is often propagated through corms. However, conventional propagation methods have limitations in terms of multiplication rate and maintaining cultivar purity. Tissue culture, also known as micropropagation, offers a solution by enabling rapid, clonal multiplication of desired gladiolus cultivars. This technique, rooted in plant biotechnology, involves the asexual propagation of plants from small pieces of plant tissue under sterile conditions. The global ornamental plant market is valued at billions of dollars, and tissue culture plays a vital role in meeting the demand for high-quality planting material.
What is Tissue Culture?
Tissue culture, fundamentally, is a method of plant propagation that uses small pieces of plant tissue (explants) on a nutrient medium under sterile conditions to produce a large number of identical plants. It bypasses the limitations of traditional propagation.
Procedure of Gladiolus Tissue Culture
The process of multiplying gladiolus cultivars through tissue culture involves several distinct stages:
1. Initiation Stage
- Explant Selection: The process begins with selecting a healthy, disease-free gladiolus plant. A small piece of corm tissue, typically a bud scale or a small portion of the corm, is excised as the explant.
- Sterilization: The explant is rigorously sterilized, usually with sodium hypochlorite (NaOCl) or mercuric chloride (HgCl2) to eliminate surface contaminants. This is crucial to prevent fungal or bacterial contamination.
- Culture Medium: The sterilized explant is placed on a nutrient-rich medium containing macro and micronutrients, vitamins, sugars (usually sucrose), and plant growth regulators (PGRs). Common PGRs include auxins (e.g., NAA - α-Naphthaleneacetic acid) and cytokinins (e.g., BAP - 6-Benzylaminopurine).
2. Multiplication Stage
- Shoot Proliferation: Under the influence of cytokinins (higher cytokinin:auxin ratio), the explant initiates shoot proliferation, forming multiple shoots. The medium is often transferred to fresh medium periodically to encourage continued growth.
- Subculturing: The newly formed shoots are subdivided and transferred to fresh media to increase the number of shoots exponentially. This is repeated several times (typically 3-4 times) to generate a large number of shoots.
3. Rooting Stage
- Root Induction: Shoots are transferred to a rooting medium containing a lower cytokinin:auxin ratio (higher auxin concentration) to induce root formation. Indole-3-acetic acid (IAA) is a commonly used auxin.
- Environmental Control: Temperature (25-28°C) and humidity are carefully controlled to promote root development.
4. Acclimatization Stage
- Gradual Transition: Plantlets with roots are gradually acclimatized to greenhouse conditions. This involves slowly reducing the humidity and increasing the light intensity.
- Potting: The acclimatized plantlets are transferred to potting mix and provided with regular watering and fertilization.
Advantages of Tissue Culture for Gladiolus
Compared to traditional corm propagation, tissue culture offers several advantages:
- Rapid Multiplication: Allows for the mass production of disease-free planting material within a short period.
- Genetic Uniformity: Ensures the production of genetically identical clones, maintaining cultivar purity.
- Disease Elimination: Can eliminate viruses and other pathogens from the parent plant material.
- Year-Round Production: Enables year-round production, independent of seasonal constraints.
| Stage | Key Components | Plant Growth Regulators (PGRs) |
|---|---|---|
| Initiation | Sterile Explant, Nutrient Medium | Low Auxin, Low Cytokinin |
| Multiplication | Fresh Medium, Subculturing | High Cytokinin:Auxin Ratio |
| Rooting | Rooting Medium | High Auxin:Cytokinin Ratio |
| Acclimatization | Greenhouse, Potting Mix | None (natural conditions) |
Conclusion
In conclusion, tissue culture is a crucial technique for the rapid and clonal propagation of gladiolus cultivars. The procedure, involving initiation, multiplication, rooting, and acclimatization, offers significant advantages over traditional methods, including disease elimination and year-round production. As biotechnology advances, further refinements in tissue culture protocols promise even more efficient and cost-effective gladiolus propagation, contributing to the flourishing of the ornamental horticulture sector.
Answer Length
This is a comprehensive model answer for learning purposes and may exceed the word limit. In the exam, always adhere to the prescribed word count.