1. Purpose of the Multiplication Stage
Shoot multiplication turns a single viable culture into hundreds or thousands of new shoots.
This is accomplished by:
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Encouraging axillary bud break
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Inducing adventitious shoot formation
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Repeating subcultures at 3–5 week intervals
This stage is cytokinin-dominant—unlike rooting or callus stages.
2. Hormonal Control – Cytokinins
Cytokinins promote:
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Cell division in shoot meristems
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Axillary bud activation
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Suppression of root initiation (temporarily)
| Cytokinin | Common Use |
|---|---|
| BAP | Universal shoot inducer for most species |
| Kinetin | Often used in leguminous plants |
| Zeatin | Less toxic, better for sensitive tissues |
| TDZ | Potent but can cause callus or vitrification if overused |
📌 Hormonal Regulation in Shoot Proliferation
3. Culture Conditions
To maximize shoot multiplication:
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Use MS or ½ MS medium + cytokinin
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Maintain pH ~5.6 before autoclaving
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Use gelling agents like agar or Gelrite
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Incubate under:
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25 ± 2°C
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16-hour photoperiod
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40–60 µmol m²/s light intensity
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Subculture every 3–4 weeks to avoid depletion of nutrients and hormones.
4. Dealing with Common Problems
| Issue | Cause | Solution |
|---|---|---|
| Hyperhydricity | High cytokinin or low agar | Reduce hormone or increase agar |
| Browning | Phenolic oxidation | Add activated charcoal or ascorbic acid |
| Uneven shoots | Nutrient imbalance | Optimize PGRs and light |
📌 Hyperhydricity in Plant Tissue Culture
5. Multiplication Potential
One node = 3–5 shoots in 3–4 weeks
One explant → 100+ plantlets in 2–3 months
This exponential potential is what makes micropropagation commercially viable.
Document every cycle to optimize:
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Hormone ratios
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Media volumes
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Light conditions