Some plants, like beet, wheat, etc., require treatment of low temperature, besides photoperiodism, in order to flowers. The treatment of cold in order to flower is called vernalization. This term was coined by Lysenko in 1928, although it was reported by Klippart in 1859. Due to vernalization, a hypothetical flowering hormone called vernalin is formed. The presence of vernalin was reported by Melchers but has never been isolated or characterised so far.
Once a plant is placed for vernalization, it can be reverted or de-vernalized by exposing the same plant at a temperature above 30oC. Vernalin, the hypothetical hormone is synthesised at the shoot apical meristems and affects the same organ.
Several factors are needed for vernalization:
1. The vernalization process needs the presence of oxygen.
2. The tenure of treatment must be for a longer time, one to one and a half months.
3. Optimum temperature is 1-6oC. It is observed that above 7oC the effect declines.
4. Optimum hydration is absolutely necessary for the process.