1. What is Acclimatization?

Acclimatization is the critical transition phase where tissue-cultured plants are shifted from the highly controlled in vitro environment to open, non-sterile conditions.

It involves gradually introducing the plants to:

• Normal humidity levels

• Ambient light intensity

• Non-sugar-based nutrient uptake

• Soil microbial communities

This helps them rebuild natural defenses and regain physiological independence.

2. The Problem with In Vitro Plantlets

Plantlets in culture vessels are:

• Dependent on sucrose rather than photosynthesis

• Grown in high humidity with minimal transpiration

• Lacking functional cuticles and stomata

• Not accustomed to wind, temperature variation, or soil microbes

If planted directly into soil, they often wilt and die from water loss, light shock, or infection.

3. Key Biological Adjustments

Successful acclimatization allows:

These changes can take several days to weeks, depending on the species and growing conditions.

4. General Stages of Acclimatization

1. Potting: Plants are transferred from agar to moist, sterile potting mix

2. Humidity Protection: Covered with a dome or misted to maintain RH ~90%

3. Gradual Transition: Over 7–14 days, humidity is reduced, light intensity increased

4. Greenhouse Transfer: Hardened plants are moved to greenhouse or shadehouse

📌 Hardening-Off Procedures for Micropropagated Plants

5. Acclimatization Equipment

• Substrate: Sterile mix of peat, coco coir, vermiculite

• Humidity Control: Clear plastic domes, transparent boxes, or mist chambers

• Lighting: Filtered or shaded light to prevent shock

• Irrigation: Misting system or manual spray bottle

• Optional: Trays with drainage, heating pads, antifungal dips

The more gradual and consistent the environment, the higher the survival rate.