Acclimation is one of the highest-risk stages of micropropagation because an in-vitro plantlet is being moved from a protected culture vessel into an environment with very different humidity, light, microbial exposure and root-zone physics.
Why tissue-culture plants wilt
Plantlets developed at very high humidity can lose water faster than their roots can replace it after transfer. Root systems formed in vitro may also need time to become effective in a porous ex-vitro substrate.
Why roots rot after deflasking
Keeping the new substrate saturated is a common response to wilting, but this can reduce oxygen availability around roots. High humidity should protect the shoot while an aerated medium protects the root zone; these are separate requirements.
Leaf loss
Some in-vitro foliage may be poorly adapted to the new environment. Losing older leaves is not automatically fatal if the meristem and roots remain viable and new ex-vitro growth begins. Rapid whole-plant collapse, soft tissue or spreading lesions require closer investigation.
Light stress
Move plantlets into useful light gradually. A sudden increase in irradiance can increase leaf temperature and transpiration before stomatal control and root uptake are ready to compensate.
Humidity reduction
Do not treat acclimation as a race to remove a dome. Reduce humidity in response to plant performance and new growth. The goal is progressive development of functional ex-vitro water relations rather than an arbitrary number of days enclosed.
Contamination after transfer
Ex-vitro conditions are not sterile. Clean technique reduces the initial pathogen load, but a healthy substrate-air balance and avoidance of persistent free water are also important once plants leave culture.
Related troubleshooting
Start with our tissue-culture acclimation guide, then read about tissue-culture contamination and humidity, VPD and airflow.
Need a tissue culture project assessed?
For commercial propagation or specialist micropropagation enquiries, see our Plant Tissue Culture Services UK page.