Here’s a professional, course-ready section on Plant Growth Regulators (PGRs) for COPI’s Agarwood Tissue Culture Course, designed for SOP manuals, lab guides, and technician training:
Plant Growth Regulators in Aquilaria Tissue Culture
1. Importance
Plant Growth Regulators (PGRs) are essential chemical signals that control:
- Cell division and differentiation
- Shoot and root induction
- Callus formation and somatic embryogenesis
- Organogenesis efficiency and plantlet vigor
Proper PGR selection and balance directly influence regeneration success and long-term plantlet quality in Aquilaria tissue culture.
2. Major Classes of PGRs
2.1 Auxins
| Auxin Type | Typical Concentration | Role in Aquilaria Tissue Culture |
|---|---|---|
| Indole-3-acetic acid (IAA) | 0.1–1.0 mg/L | Natural auxin; stimulates cell elongation and rooting |
| Indole-3-butyric acid (IBA) | 0.1–2.0 mg/L | Promotes root induction; often used for shoot tip and nodal explants |
| Naphthaleneacetic acid (NAA) | 0.1–2.0 mg/L | Induces callus and root formation; can be combined with cytokinins for organogenesis |
| 2,4-Dichlorophenoxyacetic acid (2,4-D) | 0.5–2.0 mg/L | Strong callus inducer; used for indirect organogenesis and somatic embryogenesis |
Key Notes:
- Auxin concentration influences callus vs. root induction.
- High auxin levels may inhibit shoot regeneration.
2.2 Cytokinins
| Cytokinin Type | Typical Concentration | Role in Aquilaria Tissue Culture |
|---|---|---|
| 6-Benzylaminopurine (BAP) | 0.5–3.0 mg/L | Stimulates shoot proliferation; enhances bud break in nodal cultures |
| Kinetin (KIN) | 0.5–2.0 mg/L | Promotes shoot multiplication and leaf expansion |
| Thidiazuron (TDZ) | 0.01–0.5 mg/L | Highly active; induces adventitious shoots and somatic embryos |
Key Notes:
- Cytokinins favor shoot induction and bud multiplication.
- Auxin-to-cytokinin ratio is critical for morphogenic outcomes.
2.3 Gibberellins (GA₃)
| GA Type | Typical Concentration | Role in Aquilaria Tissue Culture |
|---|---|---|
| Gibberellic acid (GA₃) | 0.1–1.0 mg/L | Promotes shoot elongation, reduces vitrification, and improves plantlet vigor |
Key Notes:
- GA₃ is usually combined with cytokinins during elongation phase.
- Excess GA₃ can cause excessive elongation and weak shoots.
3. Auxin–Cytokinin Balance Principle
| Effect | Auxin > Cytokinin | Auxin ≈ Cytokinin | Cytokinin > Auxin |
|---|---|---|---|
| Response | Root induction | Callus formation | Shoot induction / bud multiplication |
Manipulating auxin–cytokinin ratio allows targeted morphogenesis in Aquilaria tissue culture.
4. Practical Guidelines (COPI Standard)
- Explant type matters:
- Nodal/shoot tip → higher cytokinin for shoot multiplication
- Leaf/hypocotyl → higher auxin for callus induction
- PGR combinations:
- Use low auxin + moderate cytokinin for direct organogenesis
- Use 2,4-D + cytokinin for indirect organogenesis
- Concentration optimization:
- Start with literature-based range; adjust based on species and explant response
- Addition to media:
- Heat-sensitive PGRs must be filter-sterilized and added post-autoclaving
5. Key Principles for COPI Labs
- Maintain batch records for each PGR combination
- Monitor for hyperhydricity, callus browning, or abnormal growth
- Adjust auxin-cytokinin ratio based on explant and culture stage
- Ensure traceability of PGR stock solutions for reproducibility
6. Course-Ready Key Statement
PGRs are the master regulators of Aquilaria tissue culture. Careful selection, concentration, and balance of auxins, cytokinins, and gibberellins determine whether an explant forms roots, shoots, or callus, and ultimately influence the regeneration efficiency, plantlet vigor, and resin-yield potential of propagated plantlets.
I can next:
- Create a visual infographic showing PGR types, concentrations, explant-specific responses, and auxin:cytokinin balance
- Include a decision chart for morphogenesis pathway per explant type
- Integrate this into Module 2.5 of your course manual
Do you want me to create the visual infographic version next?