Photoperiodism and Vernalisation



Photoperiodism is the response of plants and animals to the relative lengths of light and dark periods. In plants, the most significant photoperiodic response is the initiation of flowering. The photoperiodism was been first observed in Maryland Mammoth variety of tobacco.

Based on the duration of plants to the light, it is further classified into  three categories:

  1. Long day plants- Example: Spinach, hibiscus, etc.
  2. Short day plants- Example: Sugarcane, cotton, etc.
  3. Day-neutral plants- Example:Tomato,rose, etc.

Apart from plant species certain birds and animals also respond during certain times of the year by showing certain behaviors. A number of biological and behavioral changes are dependent on the photoperiodism that includes migration, reproduction, and the changing of coats, etc. For example, the bird nightingale sings more frequently during the breeding seasons


Vernalization is the process of accelerating the ability of the flowering in plants by a chilling treatment. In this technique, a cold treatment is given especially to flower buds, seeds or seedlings. This type of process is mainly carried out for promoting early flowering in plants. In the year 1920, a Russian scientist T.D. Lysenko first introduced the term vernalization.

Vernalisation process was introduced on several species of biennials and perennials plants in order to produce flowers at the low temperature ranging between 1oC to 12 oC.

Differences between  Photoperiodism and Vernalisation

Photoperiodism Vernalisation
The response to the lengths of day and nights or light and dark period. The acceleration of the ability to produce flowers with a chilling treatment.
Mediated through Florigen. Mediated through Vernalin.
Provides both stimulus and induction of flowering. Prepare a plant for perceiving the flowering stimulus.
Gibberellin acid can replace exposure to long photoperiods. Gibberellin acid can replace cold treatment to induce vernalization.
Exposure to 2 to 3 appropriate photoperiods. Exposure to the low temperature between 1°C to 12°C for about 50 days required to induce flowering.

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Photoperiodism was first characterized in