Photoperiodism and Vernalisation

Photoperiodism

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.

Photoperiodism

Photoperiodism

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 behaviours. A number of biological and behavioural 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.

Also Read: Seed germination

Vernalisation

Vernalisation

Vernalization

Vernalisation is the process of accelerating the ability of the flowering in plants by exposing them to cold temperatures. In this technique, 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 vernalisation.

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.

Difference between  Photoperiodism and Vernalisation

Following are the important difference between photoperiodism and vernalization:

Photoperiodism

Vernalisation

Induction of flowering in plants by exposing them to light and dark photoperiods.

Induction of flowering in plants by exposing them to cold temperatures.

It provides stimuli in addition to flowering induction.

It only prepares the plant to perceive flowering stimuli. It does not induce flowering.

The light stimulus in photoperiodism is only received by green leaves.

The cold treatment stimulus is received by leaves, embryo, and meristem.

Photoperiodism is mediated by a hypothetical hormone Florigen.

Vernalisation is mediated by a hypothetical hormone vernalin.

2-3 photoperiods are enough to induce flowering.

Exposure to low temperatures for 50 days induces flowering.

Gibberellic acid can replace exposure to long photoperiods only in long-day plants.

Gibberellic acid can replace cold treatments to induce vernalisation in all plants.

Photoperiodism can be nullified by exposing to unfavourable photoperiods.

Vernalisation can be nullified by exposing them to high temperatures.

Also Read: Seed Dormancy

For more detailed information on photoperiodism and vernalisation, keep visiting BYJU’S website or download BYJU’S app for further reference.

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