- Water and Oxygen
Seed need to imbibe 20 10% water. Therefore, dry seed cannot be vernalized. Similarly oxygen is also necessary for vernalization. Oxygen is used during respiration. A germinating seed need energy. This energy is provided by respiration. The inhibition of respiration blocks the process of vernalization.
The seeds are exposed to low temperature during vernalization. This temperature ranges from I — 7°C. Temperature lower than 4°C is not effective. Similarly, temperature above 12°C does not cause vernalization. The duration of vernalization varies in different species. It varies from 10 to 100 days. The period of 8. week is quite effective for vernalization in most of the species.
The exposing of vernalized seed to high temperature lost the effect of vernalization. It is called Devernalization. It occurs in case of suboptimal vernalization. The temperature above 30 -35°C is effective for devernalization. However, the optimum vernalization cannot be devernalized.
- Food substances
Food substances are required for respiration. Isolated embryos cannot be vernalized.
- Effect of light
Light has no effect on the process of vernalization. Thus seed of a plant can be vernalized in the presence or absence of light. But many plants like carrot require both vernalization and photoperiodic stimulus. They must be first vernalized. Then are given photoperiodic stimulus for flowering.
- Effect of hormones
Many species like carrot and Hyoscyamus have obligate vernalization requirement. They are rosette in habit during vegetative stage. These .plants show rapid flowering after vernalization. It also causes elongation or bolting in plant. The requirement of vernalization can be replaced by application of gibberellic acid. It causes both bolting and flowering.