Vernalization : Definition and its Significance MCQ - Practice Questions with Answers

• Vernalisation refers especially to the promotion of flowering by a period of low temperature. 
• It prevents precocious reproductive development late in the growing season, and enables the plant to have sufficient time to reach maturity.
• The term was coined by Lysenko.
• Vernalisation simply prepares a plant to flower. It makes the plant perceptive to the stimulus; however, it itself does not function as a stimulus.
• Site of Vernalisation (Site of Perception): The stimulus of vernalization is perceived only by the meristem­atic cells, e.g., shoot tip, embryo tips, root apex, developing leaves, etc..

Requirements of Vernalization:

1. Low Temperature: Temperature required for vernalization is usually 0°—5°. It is 3°—17° in case of biennial Henbane (Hyoscyamus niger). Low temperature treatment should not be immediately followed by very high temperature (about 40°C) otherwise the effect of vernalization is lost. The phenomenon is called de-vernalization.

2. Actively Dividing Cells: Vernalization does not occur in dry seeds. The seeds must be germinated so that they contain an active embryo. For this the seeds are moistened before exposing them to low temperature. In whole plants, an active meristem is required.

3. Water: Proper protoplasmic hydration is a must for perceiving the stimulus of vernalization.

4. Aerobic respiration and proper nourishment.
 

• Vernalization is perceived in the form of vernalin.
• It can be passed from one plant to another through grafting in case of Henbane but not in others. 
• However, the chemical has not been separated. In some plants, cold treatment can be replaced by gibberellins.
• The formation of vernalin is not enough to bring about vernalisation.
• In addition, a suitable day length is also necessary. 

Significance of Vernalization:

(i) Vernalisation can help in shortening the juvenile or vegetative period of plant and induce early flowering. It is applicable to not only temperate plants but also to tropical plants, e.g., wheat, rice, millets, cotton.

(ii) It increases yield, resistance to cold and diseases.

(iii) It enables the biennials to behave as annuals.

(iv) Plants can be grown in such regions where normally they do not grow